Discussion:
brahma
(too old to reply)
umashankar manthravadi
2017-01-02 06:57:40 UTC
Permalink
Raw Message
This is just an announcement that Nakul Sood and Embrace video will no longer be manufacturing or selling Brahma ambisonic microphones. Our very informal arrangement has come to an end as Nakul Sood demanded 1)I hand over complete technology and manufacturing protocols, 2) sign a non-disclosure agreement and 3) sign a non-compete agreement. (there were other demands) I have always worked on Brahma as a shared project, with help from many people and I have no desire to sign a non-disclosure agreement.

I had made atleast 20 Brahma microphones before this project began, and I will continue to make one off brahmas as demanded (I am currently making five second order microphones for Angelo Farina) and I am setting up fairly high tech processes in Bangalore where I now live (laser cut microphone bodies!)

Umashankar

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

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Dave Malham
2017-01-02 11:13:42 UTC
Permalink
Raw Message
Just to wish you good luck with this project in this New Year!

Dave

On 2 January 2017 at 06:57, umashankar manthravadi <***@hotmail.com>
wrote:

> This is just an announcement that Nakul Sood and Embrace video will no
> longer be manufacturing or selling Brahma ambisonic microphones. Our very
> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
> over complete technology and manufacturing protocols, 2) sign a
> non-disclosure agreement and 3) sign a non-compete agreement. (there were
> other demands) I have always worked on Brahma as a shared project, with
> help from many people and I have no desire to sign a non-disclosure
> agreement.
>
> I had made atleast 20 Brahma microphones before this project began, and I
> will continue to make one off brahmas as demanded (I am currently making
> five second order microphones for Angelo Farina) and I am setting up fairly
> high tech processes in Bangalore where I now live (laser cut microphone
> bodies!)
>
> Umashankar
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
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> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>



--

As of 1st October 2012, I have retired from the University.

These are my own views and may or may not be shared by the University

Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Gerard Lardner
2017-01-02 14:01:18 UTC
Permalink
Raw Message
Sorry to hear of the falling-out. I have had some issues with the
build-quality of my Brahma, which was made by Embrace Video, but
nevertheless it remains my 'go-to' mic for choral recording.

With best wishes for 2017, and for your ongoing Ambisonic microphone
projects,

Gerard


On 02/01/2017 06:57, umashankar manthravadi wrote:
> This is just an announcement that Nakul Sood and Embrace video will no longer be manufacturing or selling Brahma ambisonic microphones. Our very informal arrangement has come to an end as Nakul Sood demanded 1)I hand over complete technology and manufacturing protocols, 2) sign a non-disclosure agreement and 3) sign a non-compete agreement. (there were other demands) I have always worked on Brahma as a shared project, with help from many people and I have no desire to sign a non-disclosure agreement.
>
> I had made atleast 20 Brahma microphones before this project began, and I will continue to make one off brahmas as demanded (I am currently making five second order microphones for Angelo Farina) and I am setting up fairly high tech processes in Bangalore where I now live (laser cut microphone bodies!)
>
> Umashankar
>

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Bo-Erik Sandholm
2017-01-03 05:59:18 UTC
Permalink
Raw Message
Good luck in your continued effekt.

By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
capsules.
I have not yet assembler it.
I Wonder is there any software package and description on How to create
calibration files for The mic?
I will probably have The possibility to get temporary access to a anechoic
room.
In worst case i Will use the generic calibration from sennheiser :-)

The mechanical size of The tetraeder is about right.
Bo-Erik



Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:

> Sorry to hear of the falling-out. I have had some issues with the
> build-quality of my Brahma, which was made by Embrace Video, but
> nevertheless it remains my 'go-to' mic for choral recording.
>
> With best wishes for 2017, and for your ongoing Ambisonic microphone
> projects,
>
> Gerard
>
>
> On 02/01/2017 06:57, umashankar manthravadi wrote:
>
>> This is just an announcement that Nakul Sood and Embrace video will no
>> longer be manufacturing or selling Brahma ambisonic microphones. Our very
>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>> over complete technology and manufacturing protocols, 2) sign a
>> non-disclosure agreement and 3) sign a non-compete agreement. (there were
>> other demands) I have always worked on Brahma as a shared project, with
>> help from many people and I have no desire to sign a non-disclosure
>> agreement.
>>
>> I had made atleast 20 Brahma microphones before this project began, and I
>> will continue to make one off brahmas as demanded (I am currently making
>> five second order microphones for Angelo Farina) and I am setting up fairly
>> high tech processes in Bangalore where I now live (laser cut microphone
>> bodies!)
>>
>> Umashankar
>>
>>
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> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
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umashankar manthravadi
2017-01-03 06:46:58 UTC
Permalink
Raw Message
Don't call it tetramic. It will upset len Moskowitz.
I use a process developed by Angelo Farina's team, using Matlab scripts. Initially, I was given permission only to use it, but not share it, but a few months ago, Angelo said I can forward the scripts to Marc Lavallee, who is modifying them to run on Octave. Octave is a free program, and these scripts will be released to public, so it should be possible for anyone who builds a tetrahedral microphone to calibrate it and generate filtermatrix files. These files can be used with VVEncode (purchased) or X-volver (free) to produce B format files.
In the meantime, I am willing to create filtermatrix files for anyone who wants to do their own measurements. (Fons will also do it, but mostly he does it for Linux)
You do not need an anechoic chamber. You need a space with the first reflection atleast 2.5 metres away. A room with a five meter high ceiling and dimensions of 7.5 meters by 5 meters will be adequate. You can use Angelo's inverse sine sweep. I will describe my process in detail if you wish, but I am very happy with the imaging I am getting with Brahma microphones. The tetrahedral structure printed by Shapeways is very accurate, and that helps too.

Umashankar
Don't use sennheiser's generic filters. Their capsules are also 14 mm, but they are spaced much further apart (mine are almost at the theoretical minimum). At the AES, the Sennheiser booth was next to Brahma, and many people compared the imaging of the two.

Umashankar

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: Bo-Erik Sandholm<mailto:***@gmail.com>
Sent: Tuesday, January 3, 2017 11:29 AM
To: sursound<mailto:***@music.vt.edu>; ***@iol.ie<mailto:***@iol.ie>
Subject: Re: [Sursound] [allowed] brahma

Good luck in your continued effekt.

By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
capsules.
I have not yet assembler it.
I Wonder is there any software package and description on How to create
calibration files for The mic?
I will probably have The possibility to get temporary access to a anechoic
room.
In worst case i Will use the generic calibration from sennheiser :-)

The mechanical size of The tetraeder is about right.
Bo-Erik



Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:

> Sorry to hear of the falling-out. I have had some issues with the
> build-quality of my Brahma, which was made by Embrace Video, but
> nevertheless it remains my 'go-to' mic for choral recording.
>
> With best wishes for 2017, and for your ongoing Ambisonic microphone
> projects,
>
> Gerard
>
>
> On 02/01/2017 06:57, umashankar manthravadi wrote:
>
>> This is just an announcement that Nakul Sood and Embrace video will no
>> longer be manufacturing or selling Brahma ambisonic microphones. Our very
>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>> over complete technology and manufacturing protocols, 2) sign a
>> non-disclosure agreement and 3) sign a non-compete agreement. (there were
>> other demands) I have always worked on Brahma as a shared project, with
>> help from many people and I have no desire to sign a non-disclosure
>> agreement.
>>
>> I had made atleast 20 Brahma microphones before this project began, and I
>> will continue to make one off brahmas as demanded (I am currently making
>> five second order microphones for Angelo Farina) and I am setting up fairly
>> high tech processes in Bangalore where I now live (laser cut microphone
>> bodies!)
>>
>> Umashankar
>>
>>
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> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
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***@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.

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seva, soundcurrent mastering
2017-01-03 10:29:49 UTC
Permalink
Raw Message
umashankar, i send my best wishes for the New Year and for your microphone
building!

seva

On Tue, Jan 3, 2017 at 1:46 AM, umashankar manthravadi <
***@hotmail.com> wrote:

> Don't call it tetramic. It will upset len Moskowitz.
> I use a process developed by Angelo Farina's team, using Matlab scripts.
> Initially, I was given permission only to use it, but not share it, but a
> few months ago, Angelo said I can forward the scripts to Marc Lavallee, who
> is modifying them to run on Octave. Octave is a free program, and these
> scripts will be released to public, so it should be possible for anyone who
> builds a tetrahedral microphone to calibrate it and generate filtermatrix
> files. These files can be used with VVEncode (purchased) or X-volver (free)
> to produce B format files.
> In the meantime, I am willing to create filtermatrix files for anyone who
> wants to do their own measurements. (Fons will also do it, but mostly he
> does it for Linux)
> You do not need an anechoic chamber. You need a space with the first
> reflection atleast 2.5 metres away. A room with a five meter high ceiling
> and dimensions of 7.5 meters by 5 meters will be adequate. You can use
> Angelo's inverse sine sweep. I will describe my process in detail if you
> wish, but I am very happy with the imaging I am getting with Brahma
> microphones. The tetrahedral structure printed by Shapeways is very
> accurate, and that helps too.
>
> Umashankar
> Don't use sennheiser's generic filters. Their capsules are also 14 mm, but
> they are spaced much further apart (mine are almost at the theoretical
> minimum). At the AES, the Sennheiser booth was next to Brahma, and many
> people compared the imaging of the two.
>
> Umashankar
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
> From: Bo-Erik Sandholm<mailto:***@gmail.com>
> Sent: Tuesday, January 3, 2017 11:29 AM
> To: sursound<mailto:***@music.vt.edu>; ***@iol.ie<mailto:glardne
> ***@iol.ie>
> Subject: Re: [Sursound] [allowed] brahma
>
> Good luck in your continued effekt.
>
> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> capsules.
> I have not yet assembler it.
> I Wonder is there any software package and description on How to create
> calibration files for The mic?
> I will probably have The possibility to get temporary access to a anechoic
> room.
> In worst case i Will use the generic calibration from sennheiser :-)
>
> The mechanical size of The tetraeder is about right.
> Bo-Erik
>
>
>
> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>
> > Sorry to hear of the falling-out. I have had some issues with the
> > build-quality of my Brahma, which was made by Embrace Video, but
> > nevertheless it remains my 'go-to' mic for choral recording.
> >
> > With best wishes for 2017, and for your ongoing Ambisonic microphone
> > projects,
> >
> > Gerard
> >
> >
> > On 02/01/2017 06:57, umashankar manthravadi wrote:
> >
> >> This is just an announcement that Nakul Sood and Embrace video will no
> >> longer be manufacturing or selling Brahma ambisonic microphones. Our
> very
> >> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
> >> over complete technology and manufacturing protocols, 2) sign a
> >> non-disclosure agreement and 3) sign a non-compete agreement. (there
> were
> >> other demands) I have always worked on Brahma as a shared project, with
> >> help from many people and I have no desire to sign a non-disclosure
> >> agreement.
> >>
> >> I had made atleast 20 Brahma microphones before this project began, and
> I
> >> will continue to make one off brahmas as demanded (I am currently making
> >> five second order microphones for Angelo Farina) and I am setting up
> fairly
> >> high tech processes in Bangalore where I now live (laser cut microphone
> >> bodies!)
> >>
> >> Umashankar
> >>
> >>
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
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> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> > edit account or options, view archives and so on.
> >
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> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
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> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
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>
>


--
best
seva

***@soundcurrent.com
www.soundcurrent.com
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Augustine Leudar
2017-01-03 14:15:32 UTC
Permalink
Raw Message
Good Luck Umashankar a\nd Happy New Year !!

On 3 January 2017 at 10:29, seva, soundcurrent mastering <
***@soundcurrent.com> wrote:

> umashankar, i send my best wishes for the New Year and for your microphone
> building!
>
> seva
>
> On Tue, Jan 3, 2017 at 1:46 AM, umashankar manthravadi <
> ***@hotmail.com> wrote:
>
> > Don't call it tetramic. It will upset len Moskowitz.
> > I use a process developed by Angelo Farina's team, using Matlab scripts.
> > Initially, I was given permission only to use it, but not share it, but a
> > few months ago, Angelo said I can forward the scripts to Marc Lavallee,
> who
> > is modifying them to run on Octave. Octave is a free program, and these
> > scripts will be released to public, so it should be possible for anyone
> who
> > builds a tetrahedral microphone to calibrate it and generate filtermatrix
> > files. These files can be used with VVEncode (purchased) or X-volver
> (free)
> > to produce B format files.
> > In the meantime, I am willing to create filtermatrix files for anyone who
> > wants to do their own measurements. (Fons will also do it, but mostly he
> > does it for Linux)
> > You do not need an anechoic chamber. You need a space with the first
> > reflection atleast 2.5 metres away. A room with a five meter high ceiling
> > and dimensions of 7.5 meters by 5 meters will be adequate. You can use
> > Angelo's inverse sine sweep. I will describe my process in detail if you
> > wish, but I am very happy with the imaging I am getting with Brahma
> > microphones. The tetrahedral structure printed by Shapeways is very
> > accurate, and that helps too.
> >
> > Umashankar
> > Don't use sennheiser's generic filters. Their capsules are also 14 mm,
> but
> > they are spaced much further apart (mine are almost at the theoretical
> > minimum). At the AES, the Sennheiser booth was next to Brahma, and many
> > people compared the imaging of the two.
> >
> > Umashankar
> >
> > Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> > Windows 10
> >
> > From: Bo-Erik Sandholm<mailto:***@gmail.com>
> > Sent: Tuesday, January 3, 2017 11:29 AM
> > To: sursound<mailto:***@music.vt.edu>; ***@iol.ie<mailto:
> glardne
> > ***@iol.ie>
> > Subject: Re: [Sursound] [allowed] brahma
> >
> > Good luck in your continued effekt.
> >
> > By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> > capsules.
> > I have not yet assembler it.
> > I Wonder is there any software package and description on How to create
> > calibration files for The mic?
> > I will probably have The possibility to get temporary access to a
> anechoic
> > room.
> > In worst case i Will use the generic calibration from sennheiser :-)
> >
> > The mechanical size of The tetraeder is about right.
> > Bo-Erik
> >
> >
> >
> > Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
> >
> > > Sorry to hear of the falling-out. I have had some issues with the
> > > build-quality of my Brahma, which was made by Embrace Video, but
> > > nevertheless it remains my 'go-to' mic for choral recording.
> > >
> > > With best wishes for 2017, and for your ongoing Ambisonic microphone
> > > projects,
> > >
> > > Gerard
> > >
> > >
> > > On 02/01/2017 06:57, umashankar manthravadi wrote:
> > >
> > >> This is just an announcement that Nakul Sood and Embrace video will no
> > >> longer be manufacturing or selling Brahma ambisonic microphones. Our
> > very
> > >> informal arrangement has come to an end as Nakul Sood demanded 1)I
> hand
> > >> over complete technology and manufacturing protocols, 2) sign a
> > >> non-disclosure agreement and 3) sign a non-compete agreement. (there
> > were
> > >> other demands) I have always worked on Brahma as a shared project,
> with
> > >> help from many people and I have no desire to sign a non-disclosure
> > >> agreement.
> > >>
> > >> I had made atleast 20 Brahma microphones before this project began,
> and
> > I
> > >> will continue to make one off brahmas as demanded (I am currently
> making
> > >> five second order microphones for Angelo Farina) and I am setting up
> > fairly
> > >> high tech processes in Bangalore where I now live (laser cut
> microphone
> > >> bodies!)
> > >>
> > >> Umashankar
> > >>
> > >>
> > > -------------- next part --------------
> > > An HTML attachment was scrubbed...
> > > URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
> > > nts/20170102/572ce57e/attachment.html>
> > > _______________________________________________
> > > Sursound mailing list
> > > ***@music.vt.edu
> > > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> > > edit account or options, view archives and so on.
> > >
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <https://mail.music.vt.edu/mailman/private/sursound/
> > attachments/20170103/f956a4dd/attachment.html>
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> > edit account or options, view archives and so on.
> >
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <https://mail.music.vt.edu/mailman/private/sursound/
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> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> > edit account or options, view archives and so on.
> >
> >
>
>
> --
> best
> seva
>
> ***@soundcurrent.com
> www.soundcurrent.com
> -------------- next part --------------
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> _______________________________________________
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> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>



--
Augustine Leudar
Artistic Director Magik Door LTD
Company Number : NI635217
Registered 63 Ballycoan rd,
Belfast BT88LL
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Augustine Leudar
2017-01-03 14:20:32 UTC
Permalink
Raw Message
I think thats the one I made Bo (mine was the velan) - I wrote a max patch
for extracting B format from the A format (it was a while ago) and I wrote
a paper as part of my masters years ago on callibration etc which you can
read here :

https://www.researchgate.net/publication/267626535_Practical_guide_to_designing_the_Velan_6_Capsule_Ambisonic_Microphone

Happy to send you the patch if its any use.



On 3 January 2017 at 05:59, Bo-Erik Sandholm <***@gmail.com> wrote:

> Good luck in your continued effekt.
>
> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> capsules.
> I have not yet assembler it.
> I Wonder is there any software package and description on How to create
> calibration files for The mic?
> I will probably have The possibility to get temporary access to a anechoic
> room.
> In worst case i Will use the generic calibration from sennheiser :-)
>
> The mechanical size of The tetraeder is about right.
> Bo-Erik
>
>
>
> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>
> > Sorry to hear of the falling-out. I have had some issues with the
> > build-quality of my Brahma, which was made by Embrace Video, but
> > nevertheless it remains my 'go-to' mic for choral recording.
> >
> > With best wishes for 2017, and for your ongoing Ambisonic microphone
> > projects,
> >
> > Gerard
> >
> >
> > On 02/01/2017 06:57, umashankar manthravadi wrote:
> >
> >> This is just an announcement that Nakul Sood and Embrace video will no
> >> longer be manufacturing or selling Brahma ambisonic microphones. Our
> very
> >> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
> >> over complete technology and manufacturing protocols, 2) sign a
> >> non-disclosure agreement and 3) sign a non-compete agreement. (there
> were
> >> other demands) I have always worked on Brahma as a shared project, with
> >> help from many people and I have no desire to sign a non-disclosure
> >> agreement.
> >>
> >> I had made atleast 20 Brahma microphones before this project began, and
> I
> >> will continue to make one off brahmas as demanded (I am currently making
> >> five second order microphones for Angelo Farina) and I am setting up
> fairly
> >> high tech processes in Bangalore where I now live (laser cut microphone
> >> bodies!)
> >>
> >> Umashankar
> >>
> >>
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
> > nts/20170102/572ce57e/attachment.html>
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> > edit account or options, view archives and so on.
> >
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> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
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--
Augustine Leudar
Artistic Director Magik Door LTD
Company Number : NI635217
Registered 63 Ballycoan rd,
Belfast BT88LL
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Fernando Lopez-Lezcano
2017-01-04 18:57:37 UTC
Permalink
Raw Message
On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
> Good luck in your continued effekt.
>
> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> capsules.
> I have not yet assembler it.
> I Wonder is there any software package and description on How to create
> calibration files for The mic?
> I will probably have The possibility to get temporary access to a anechoic
> room.

Hi Bo-Erik,
You could take a look at my project here (I posted about this a while back):

https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
(there is mailing list with 0 posts so far, ha ha..)

See paper here (been working on this for over a year):
https://ccrma.stanford.edu/~nando/publications/sphear.pdf

The project includes free software (open source, GPL) that runs in
Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
can be used directly with TetraProc (by Fons Adriansen) - or any other
software that can run the filters.

Just a few days ago I _finally_ managed to get the software into
somewhat usable shape in that I think (and I'm pretty much wrong every
time I say this, so...) it is working correctly. The calibration relies
on having 16 measurements (could be 8) in the horizontal plane around
the Ambisonics microphone plus one more of a calibration microphone in
the same exact location. Aliki is used to capture the IRs and edit (trim
and window) them. DRC (Digital Room Correction) is used to equalize the
excitation speaker. Then the software I wrote processes those IRs and
outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
a couple of pictures later...

Documentation (surprise!) is mostly lacking. I hope to remedy that
somewhat soon (at least a list of the sequence of octave function calls
you need to get the job done).

My latest prototype with 10mm capsules was hastily measured before I
left for "vacation" and the plotted results of the calibration are
looking good. A re-calibration with the latest software of my first
prototype which captured a full concert also sounds fairly decent.

Anyway,
Good luck!
-- Fernando



> In worst case i Will use the generic calibration from sennheiser :-)
>
> The mechanical size of The tetraeder is about right.
> Bo-Erik
>
>
>
> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>
>> Sorry to hear of the falling-out. I have had some issues with the
>> build-quality of my Brahma, which was made by Embrace Video, but
>> nevertheless it remains my 'go-to' mic for choral recording.
>>
>> With best wishes for 2017, and for your ongoing Ambisonic microphone
>> projects,
>>
>> Gerard
>>
>>
>> On 02/01/2017 06:57, umashankar manthravadi wrote:
>>
>>> This is just an announcement that Nakul Sood and Embrace video will no
>>> longer be manufacturing or selling Brahma ambisonic microphones. Our very
>>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>>> over complete technology and manufacturing protocols, 2) sign a
>>> non-disclosure agreement and 3) sign a non-compete agreement. (there were
>>> other demands) I have always worked on Brahma as a shared project, with
>>> help from many people and I have no desire to sign a non-disclosure
>>> agreement.
>>>
>>> I had made atleast 20 Brahma microphones before this project began, and I
>>> will continue to make one off brahmas as demanded (I am currently making
>>> five second order microphones for Angelo Farina) and I am setting up fairly
>>> high tech processes in Bangalore where I now live (laser cut microphone
>>> bodies!)
>>>
>>> Umashankar
>>>
>>>
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>> nts/20170102/572ce57e/attachment.html>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
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> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
>
umashankar manthravadi
2017-01-05 04:52:46 UTC
Permalink
Raw Message
Dear fernando



I forwarded your link to marc Lavallée when you first posted them. My intent is that we should have multiple compatible systems for calibrating A format mics



Sent from my Windows 10 phone



From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
Sent: 05 January 2017 00:28
To: Surround Sound discussion group<mailto:***@music.vt.edu>; ***@iol.ie<mailto:***@iol.ie>
Subject: Re: [Sursound] [allowed] brahma



On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
> Good luck in your continued effekt.
>
> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> capsules.
> I have not yet assembler it.
> I Wonder is there any software package and description on How to create
> calibration files for The mic?
> I will probably have The possibility to get temporary access to a anechoic
> room.

Hi Bo-Erik,
You could take a look at my project here (I posted about this a while back):

https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
(there is mailing list with 0 posts so far, ha ha..)

See paper here (been working on this for over a year):
https://ccrma.stanford.edu/~nando/publications/sphear.pdf

The project includes free software (open source, GPL) that runs in
Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
can be used directly with TetraProc (by Fons Adriansen) - or any other
software that can run the filters.

Just a few days ago I _finally_ managed to get the software into
somewhat usable shape in that I think (and I'm pretty much wrong every
time I say this, so...) it is working correctly. The calibration relies
on having 16 measurements (could be 8) in the horizontal plane around
the Ambisonics microphone plus one more of a calibration microphone in
the same exact location. Aliki is used to capture the IRs and edit (trim
and window) them. DRC (Digital Room Correction) is used to equalize the
excitation speaker. Then the software I wrote processes those IRs and
outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
a couple of pictures later...

Documentation (surprise!) is mostly lacking. I hope to remedy that
somewhat soon (at least a list of the sequence of octave function calls
you need to get the job done).

My latest prototype with 10mm capsules was hastily measured before I
left for "vacation" and the plotted results of the calibration are
looking good. A re-calibration with the latest software of my first
prototype which captured a full concert also sounds fairly decent.

Anyway,
Good luck!
-- Fernando



> In worst case i Will use the generic calibration from sennheiser :-)
>
> The mechanical size of The tetraeder is about right.
> Bo-Erik
>
>
>
> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>
>> Sorry to hear of the falling-out. I have had some issues with the
>> build-quality of my Brahma, which was made by Embrace Video, but
>> nevertheless it remains my 'go-to' mic for choral recording.
>>
>> With best wishes for 2017, and for your ongoing Ambisonic microphone
>> projects,
>>
>> Gerard
>>
>>
>> On 02/01/2017 06:57, umashankar manthravadi wrote:
>>
>>> This is just an announcement that Nakul Sood and Embrace video will no
>>> longer be manufacturing or selling Brahma ambisonic microphones. Our very
>>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>>> over complete technology and manufacturing protocols, 2) sign a
>>> non-disclosure agreement and 3) sign a non-compete agreement. (there were
>>> other demands) I have always worked on Brahma as a shared project, with
>>> help from many people and I have no desire to sign a non-disclosure
>>> agreement.
>>>
>>> I had made atleast 20 Brahma microphones before this project began, and I
>>> will continue to make one off brahmas as demanded (I am currently making
>>> five second order microphones for Angelo Farina) and I am setting up fairly
>>> high tech processes in Bangalore where I now live (laser cut microphone
>>> bodies!)
>>>
>>> Umashankar
>>>
>>>
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>> nts/20170102/572ce57e/attachment.html>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
> -------------- next part --------------
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> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
>

_______________________________________________
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https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
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Bo-Erik Sandholm
2017-01-05 10:01:35 UTC
Permalink
Raw Message
To get a good calibration, I expect I will need at least one
known/reference source or sensor?

The reference for me will probably be my coresound Tetramic.

I will probably use Kef eggs as speakers as they are coaxial transducers.
Only at low frequency will The port be offerter.

Have I understood The basics?
I will probably measure outside a calibration Day orborrow a anechoic room
at swedish radio.

Bo-Erik

Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
***@hotmail.com>:

> Dear fernando
>
>
>
> I forwarded your link to marc Lavallée when you first posted them. My
> intent is that we should have multiple compatible systems for calibrating A
> format mics
>
>
>
> Sent from my Windows 10 phone
>
>
>
> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
> Sent: 05 January 2017 00:28
> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
> ***@iol.ie<mailto:***@iol.ie>
> Subject: Re: [Sursound] [allowed] brahma
>
>
>
> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
> > Good luck in your continued effekt.
> >
> > By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> > capsules.
> > I have not yet assembler it.
> > I Wonder is there any software package and description on How to create
> > calibration files for The mic?
> > I will probably have The possibility to get temporary access to a
> anechoic
> > room.
>
> Hi Bo-Erik,
> You could take a look at my project here (I posted about this a while
> back):
>
> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
> (there is mailing list with 0 posts so far, ha ha..)
>
> See paper here (been working on this for over a year):
> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>
> The project includes free software (open source, GPL) that runs in
> Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
> can be used directly with TetraProc (by Fons Adriansen) - or any other
> software that can run the filters.
>
> Just a few days ago I _finally_ managed to get the software into
> somewhat usable shape in that I think (and I'm pretty much wrong every
> time I say this, so...) it is working correctly. The calibration relies
> on having 16 measurements (could be 8) in the horizontal plane around
> the Ambisonics microphone plus one more of a calibration microphone in
> the same exact location. Aliki is used to capture the IRs and edit (trim
> and window) them. DRC (Digital Room Correction) is used to equalize the
> excitation speaker. Then the software I wrote processes those IRs and
> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
> a couple of pictures later...
>
> Documentation (surprise!) is mostly lacking. I hope to remedy that
> somewhat soon (at least a list of the sequence of octave function calls
> you need to get the job done).
>
> My latest prototype with 10mm capsules was hastily measured before I
> left for "vacation" and the plotted results of the calibration are
> looking good. A re-calibration with the latest software of my first
> prototype which captured a full concert also sounds fairly decent.
>
> Anyway,
> Good luck!
> -- Fernando
>
>
>
> > In worst case i Will use the generic calibration from sennheiser :-)
> >
> > The mechanical size of The tetraeder is about right.
> > Bo-Erik
> >
> >
> >
> > Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
> >
> >> Sorry to hear of the falling-out. I have had some issues with the
> >> build-quality of my Brahma, which was made by Embrace Video, but
> >> nevertheless it remains my 'go-to' mic for choral recording.
> >>
> >> With best wishes for 2017, and for your ongoing Ambisonic microphone
> >> projects,
> >>
> >> Gerard
> >>
> >>
> >> On 02/01/2017 06:57, umashankar manthravadi wrote:
> >>
> >>> This is just an announcement that Nakul Sood and Embrace video will no
> >>> longer be manufacturing or selling Brahma ambisonic microphones. Our
> very
> >>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
> >>> over complete technology and manufacturing protocols, 2) sign a
> >>> non-disclosure agreement and 3) sign a non-compete agreement. (there
> were
> >>> other demands) I have always worked on Brahma as a shared project, with
> >>> help from many people and I have no desire to sign a non-disclosure
> >>> agreement.
> >>>
> >>> I had made atleast 20 Brahma microphones before this project began,
> and I
> >>> will continue to make one off brahmas as demanded (I am currently
> making
> >>> five second order microphones for Angelo Farina) and I am setting up
> fairly
> >>> high tech processes in Bangalore where I now live (laser cut microphone
> >>> bodies!)
> >>>
> >>> Umashankar
> >>>
> >>>
> >> -------------- next part --------------
> >> An HTML attachment was scrubbed...
> >> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
> >> nts/20170102/572ce57e/attachment.html>
> >> _______________________________________________
> >> Sursound mailing list
> >> ***@music.vt.edu
> >> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> >> edit account or options, view archives and so on.
> >>
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <https://mail.music.vt.edu/mailman/private/sursound/
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> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
> >
>
> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
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> _______________________________________________
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> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
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umashankar manthravadi
2017-01-05 10:19:46 UTC
Permalink
Raw Message
I use an earthworks calibration microphone, but any good quality six mm Omni microphone will be okay. Noise is not important, but flat frequency response is. You could use a tetramic and take the W signal after processing, but it might be overcomplicating things. Coaxial speakers sound ideal, but many of them have problems. A small five inch full range, or 5 inch plus tweeter mounted close together, is best. I use an Adam 5 after first sealing off the bass port. Choice of microphone is more important than the speaker.

umashankar

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: Bo-Erik Sandholm<mailto:***@gmail.com>
Sent: Thursday, January 5, 2017 3:31 PM
To: sursound<mailto:***@music.vt.edu>
Subject: Re: [Sursound] [allowed] brahma

To get a good calibration, I expect I will need at least one
known/reference source or sensor?

The reference for me will probably be my coresound Tetramic.

I will probably use Kef eggs as speakers as they are coaxial transducers.
Only at low frequency will The port be offerter.

Have I understood The basics?
I will probably measure outside a calibration Day orborrow a anechoic room
at swedish radio.

Bo-Erik

Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
***@hotmail.com>:

> Dear fernando
>
>
>
> I forwarded your link to marc Lavallée when you first posted them. My
> intent is that we should have multiple compatible systems for calibrating A
> format mics
>
>
>
> Sent from my Windows 10 phone
>
>
>
> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
> Sent: 05 January 2017 00:28
> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
> ***@iol.ie<mailto:***@iol.ie>
> Subject: Re: [Sursound] [allowed] brahma
>
>
>
> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
> > Good luck in your continued effekt.
> >
> > By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
> > capsules.
> > I have not yet assembler it.
> > I Wonder is there any software package and description on How to create
> > calibration files for The mic?
> > I will probably have The possibility to get temporary access to a
> anechoic
> > room.
>
> Hi Bo-Erik,
> You could take a look at my project here (I posted about this a while
> back):
>
> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
> (there is mailing list with 0 posts so far, ha ha..)
>
> See paper here (been working on this for over a year):
> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>
> The project includes free software (open source, GPL) that runs in
> Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
> can be used directly with TetraProc (by Fons Adriansen) - or any other
> software that can run the filters.
>
> Just a few days ago I _finally_ managed to get the software into
> somewhat usable shape in that I think (and I'm pretty much wrong every
> time I say this, so...) it is working correctly. The calibration relies
> on having 16 measurements (could be 8) in the horizontal plane around
> the Ambisonics microphone plus one more of a calibration microphone in
> the same exact location. Aliki is used to capture the IRs and edit (trim
> and window) them. DRC (Digital Room Correction) is used to equalize the
> excitation speaker. Then the software I wrote processes those IRs and
> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
> a couple of pictures later...
>
> Documentation (surprise!) is mostly lacking. I hope to remedy that
> somewhat soon (at least a list of the sequence of octave function calls
> you need to get the job done).
>
> My latest prototype with 10mm capsules was hastily measured before I
> left for "vacation" and the plotted results of the calibration are
> looking good. A re-calibration with the latest software of my first
> prototype which captured a full concert also sounds fairly decent.
>
> Anyway,
> Good luck!
> -- Fernando
>
>
>
> > In worst case i Will use the generic calibration from sennheiser :-)
> >
> > The mechanical size of The tetraeder is about right.
> > Bo-Erik
> >
> >
> >
> > Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
> >
> >> Sorry to hear of the falling-out. I have had some issues with the
> >> build-quality of my Brahma, which was made by Embrace Video, but
> >> nevertheless it remains my 'go-to' mic for choral recording.
> >>
> >> With best wishes for 2017, and for your ongoing Ambisonic microphone
> >> projects,
> >>
> >> Gerard
> >>
> >>
> >> On 02/01/2017 06:57, umashankar manthravadi wrote:
> >>
> >>> This is just an announcement that Nakul Sood and Embrace video will no
> >>> longer be manufacturing or selling Brahma ambisonic microphones. Our
> very
> >>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
> >>> over complete technology and manufacturing protocols, 2) sign a
> >>> non-disclosure agreement and 3) sign a non-compete agreement. (there
> were
> >>> other demands) I have always worked on Brahma as a shared project, with
> >>> help from many people and I have no desire to sign a non-disclosure
> >>> agreement.
> >>>
> >>> I had made atleast 20 Brahma microphones before this project began,
> and I
> >>> will continue to make one off brahmas as demanded (I am currently
> making
> >>> five second order microphones for Angelo Farina) and I am setting up
> fairly
> >>> high tech processes in Bangalore where I now live (laser cut microphone
> >>> bodies!)
> >>>
> >>> Umashankar
> >>>
> >>>
> >> -------------- next part --------------
> >> An HTML attachment was scrubbed...
> >> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
> >> nts/20170102/572ce57e/attachment.html>
> >> _______________________________________________
> >> Sursound mailing list
> >> ***@music.vt.edu
> >> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> >> edit account or options, view archives and so on.
> >>
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <https://mail.music.vt.edu/mailman/private/sursound/
> attachments/20170103/f956a4dd/attachment.html>
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
> >
>
> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
> -------------- next part --------------
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> URL: <https://mail.music.vt.edu/mailman/private/sursound/
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> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
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>
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Fernando Lopez-Lezcano
2017-01-05 19:21:08 UTC
Permalink
Raw Message
On 01/05/2017 02:19 AM, umashankar manthravadi wrote:
> I use an earthworks calibration microphone, but any good quality six mm Omni microphone will be okay. Noise is not important, but flat frequency response is. You could use a tetramic and take the W signal after processing, but it might be overcomplicating things. Coaxial speakers sound ideal, but many of them have problems. A small five inch full range, or 5 inch plus tweeter mounted close together, is best. I use an Adam 5 after first sealing off the bass port. Choice of microphone is more important than the speaker.

Indeed. I have an (if memory serves) emm6 "reference microphone" which
is not very expensive but comes with its own calibration curve. Flatness
is important as that will define how true is the frequency response of
the calibration. For the excitation I use a single driver small speaker,
so far it has been fine. I record is our rather small concert hall (the
Stage) and I managed to get about 5 mSecs of useful data before the
first reflection arrives. That seems to be enough. Completely agree with
sealing the bass port if you have one like that, that's what Eric
Benjamin recommended doing.

I'll probably be offline for a few days, sorry (vacation, no internet,
bliss)...
Good luck!
-- Fernando


> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
>
> From: Bo-Erik Sandholm<mailto:***@gmail.com>
> Sent: Thursday, January 5, 2017 3:31 PM
> To: sursound<mailto:***@music.vt.edu>
> Subject: Re: [Sursound] [allowed] brahma
>
> To get a good calibration, I expect I will need at least one
> known/reference source or sensor?
>
> The reference for me will probably be my coresound Tetramic.
>
> I will probably use Kef eggs as speakers as they are coaxial transducers.
> Only at low frequency will The port be offerter.
>
> Have I understood The basics?
> I will probably measure outside a calibration Day orborrow a anechoic room
> at swedish radio.
>
> Bo-Erik
>
> Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
> ***@hotmail.com>:
>
>> Dear fernando
>>
>>
>>
>> I forwarded your link to marc Lavallée when you first posted them. My
>> intent is that we should have multiple compatible systems for calibrating A
>> format mics
>>
>>
>>
>> Sent from my Windows 10 phone
>>
>>
>>
>> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
>> Sent: 05 January 2017 00:28
>> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
>> ***@iol.ie<mailto:***@iol.ie>
>> Subject: Re: [Sursound] [allowed] brahma
>>
>>
>>
>> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
>>> Good luck in your continued effekt.
>>>
>>> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
>>> capsules.
>>> I have not yet assembler it.
>>> I Wonder is there any software package and description on How to create
>>> calibration files for The mic?
>>> I will probably have The possibility to get temporary access to a
>> anechoic
>>> room.
>>
>> Hi Bo-Erik,
>> You could take a look at my project here (I posted about this a while
>> back):
>>
>> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
>> (there is mailing list with 0 posts so far, ha ha..)
>>
>> See paper here (been working on this for over a year):
>> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>>
>> The project includes free software (open source, GPL) that runs in
>> Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
>> can be used directly with TetraProc (by Fons Adriansen) - or any other
>> software that can run the filters.
>>
>> Just a few days ago I _finally_ managed to get the software into
>> somewhat usable shape in that I think (and I'm pretty much wrong every
>> time I say this, so...) it is working correctly. The calibration relies
>> on having 16 measurements (could be 8) in the horizontal plane around
>> the Ambisonics microphone plus one more of a calibration microphone in
>> the same exact location. Aliki is used to capture the IRs and edit (trim
>> and window) them. DRC (Digital Room Correction) is used to equalize the
>> excitation speaker. Then the software I wrote processes those IRs and
>> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
>> a couple of pictures later...
>>
>> Documentation (surprise!) is mostly lacking. I hope to remedy that
>> somewhat soon (at least a list of the sequence of octave function calls
>> you need to get the job done).
>>
>> My latest prototype with 10mm capsules was hastily measured before I
>> left for "vacation" and the plotted results of the calibration are
>> looking good. A re-calibration with the latest software of my first
>> prototype which captured a full concert also sounds fairly decent.
>>
>> Anyway,
>> Good luck!
>> -- Fernando
>>
>>
>>
>>> In worst case i Will use the generic calibration from sennheiser :-)
>>>
>>> The mechanical size of The tetraeder is about right.
>>> Bo-Erik
>>>
>>>
>>>
>>> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>>>
>>>> Sorry to hear of the falling-out. I have had some issues with the
>>>> build-quality of my Brahma, which was made by Embrace Video, but
>>>> nevertheless it remains my 'go-to' mic for choral recording.
>>>>
>>>> With best wishes for 2017, and for your ongoing Ambisonic microphone
>>>> projects,
>>>>
>>>> Gerard
>>>>
>>>>
>>>> On 02/01/2017 06:57, umashankar manthravadi wrote:
>>>>
>>>>> This is just an announcement that Nakul Sood and Embrace video will no
>>>>> longer be manufacturing or selling Brahma ambisonic microphones. Our
>> very
>>>>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>>>>> over complete technology and manufacturing protocols, 2) sign a
>>>>> non-disclosure agreement and 3) sign a non-compete agreement. (there
>> were
>>>>> other demands) I have always worked on Brahma as a shared project, with
>>>>> help from many people and I have no desire to sign a non-disclosure
>>>>> agreement.
>>>>>
>>>>> I had made atleast 20 Brahma microphones before this project began,
>> and I
>>>>> will continue to make one off brahmas as demanded (I am currently
>> making
>>>>> five second order microphones for Angelo Farina) and I am setting up
>> fairly
>>>>> high tech processes in Bangalore where I now live (laser cut microphone
>>>>> bodies!)
>>>>>
>>>>> Umashankar
>>>>>
>>>>>
>>>> -------------- next part --------------
>>>> An HTML attachment was scrubbed...
>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>>>> nts/20170102/572ce57e/attachment.html>
>>>> _______________________________________________
>>>> Sursound mailing list
>>>> ***@music.vt.edu
>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>>> edit account or options, view archives and so on.
>>>>
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>> attachments/20170103/f956a4dd/attachment.html>
>>> _______________________________________________
>>> Sursound mailing list
>>> ***@music.vt.edu
>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>>
>>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>> attachments/20170105/7f2afed4/attachment.html>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
> -------------- next part --------------
> An HTML attachment was scrubbed...
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> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
>
> -------------- next part --------------
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> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
>
David McGriffy
2017-01-06 01:54:58 UTC
Permalink
Raw Message
I recently developed a MatLab script to create calibrations based on
Angelo's method. Set up equations for each measurement's expected results,
find the LMS solution in each frequency bin, then build the resulting
filter matrix. A little engineering around the low and high frequencies
and it seems to work pretty well.

I'd also like to point out that VVEncode (alas not VVTetraVST or VVMic)
will process anyone's 4x4 matrix of filters if they are put in wav files
like Angelo and Brahma do. I also have matrix calibration processing in my
command line tool and I've done it in pure MatLab. Contact me if you want
to try this and have any questions.

I mention all this mostly because I'd be interesting in processing anyone's
custom measurements. For me this is test data for my scripts. So far I've
only run data out of one lab and with one type of
excitation/reference/etc. I'd like to make sure I'm not dependent on those
things. And I can return a working calibration, I hope.

David
VVAudio

On Thu, Jan 5, 2017 at 1:21 PM, Fernando Lopez-Lezcano <
***@ccrma.stanford.edu> wrote:

> On 01/05/2017 02:19 AM, umashankar manthravadi wrote:
>
>> I use an earthworks calibration microphone, but any good quality six mm
>> Omni microphone will be okay. Noise is not important, but flat frequency
>> response is. You could use a tetramic and take the W signal after
>> processing, but it might be overcomplicating things. Coaxial speakers sound
>> ideal, but many of them have problems. A small five inch full range, or 5
>> inch plus tweeter mounted close together, is best. I use an Adam 5 after
>> first sealing off the bass port. Choice of microphone is more important
>> than the speaker.
>>
>
> Indeed. I have an (if memory serves) emm6 "reference microphone" which is
> not very expensive but comes with its own calibration curve. Flatness is
> important as that will define how true is the frequency response of the
> calibration. For the excitation I use a single driver small speaker, so far
> it has been fine. I record is our rather small concert hall (the Stage) and
> I managed to get about 5 mSecs of useful data before the first reflection
> arrives. That seems to be enough. Completely agree with sealing the bass
> port if you have one like that, that's what Eric Benjamin recommended doing.
>
> I'll probably be offline for a few days, sorry (vacation, no internet,
> bliss)...
> Good luck!
> -- Fernando
>
>
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
>> Windows 10
>>
>> From: Bo-Erik Sandholm<mailto:***@gmail.com>
>> Sent: Thursday, January 5, 2017 3:31 PM
>> To: sursound<mailto:***@music.vt.edu>
>> Subject: Re: [Sursound] [allowed] brahma
>>
>> To get a good calibration, I expect I will need at least one
>> known/reference source or sensor?
>>
>> The reference for me will probably be my coresound Tetramic.
>>
>> I will probably use Kef eggs as speakers as they are coaxial transducers.
>> Only at low frequency will The port be offerter.
>>
>> Have I understood The basics?
>> I will probably measure outside a calibration Day orborrow a anechoic room
>> at swedish radio.
>>
>> Bo-Erik
>>
>> Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
>> ***@hotmail.com>:
>>
>> Dear fernando
>>>
>>>
>>>
>>> I forwarded your link to marc Lavallée when you first posted them. My
>>> intent is that we should have multiple compatible systems for
>>> calibrating A
>>> format mics
>>>
>>>
>>>
>>> Sent from my Windows 10 phone
>>>
>>>
>>>
>>> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
>>> Sent: 05 January 2017 00:28
>>> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
>>> ***@iol.ie<mailto:***@iol.ie>
>>> Subject: Re: [Sursound] [allowed] brahma
>>>
>>>
>>>
>>> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
>>>
>>>> Good luck in your continued effekt.
>>>>
>>>> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
>>>> capsules.
>>>> I have not yet assembler it.
>>>> I Wonder is there any software package and description on How to create
>>>> calibration files for The mic?
>>>> I will probably have The possibility to get temporary access to a
>>>>
>>> anechoic
>>>
>>>> room.
>>>>
>>>
>>> Hi Bo-Erik,
>>> You could take a look at my project here (I posted about this a while
>>> back):
>>>
>>> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
>>> (there is mailing list with 0 posts so far, ha ha..)
>>>
>>> See paper here (been working on this for over a year):
>>> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>>>
>>> The project includes free software (open source, GPL) that runs in
>>> Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
>>> can be used directly with TetraProc (by Fons Adriansen) - or any other
>>> software that can run the filters.
>>>
>>> Just a few days ago I _finally_ managed to get the software into
>>> somewhat usable shape in that I think (and I'm pretty much wrong every
>>> time I say this, so...) it is working correctly. The calibration relies
>>> on having 16 measurements (could be 8) in the horizontal plane around
>>> the Ambisonics microphone plus one more of a calibration microphone in
>>> the same exact location. Aliki is used to capture the IRs and edit (trim
>>> and window) them. DRC (Digital Room Correction) is used to equalize the
>>> excitation speaker. Then the software I wrote processes those IRs and
>>> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
>>> a couple of pictures later...
>>>
>>> Documentation (surprise!) is mostly lacking. I hope to remedy that
>>> somewhat soon (at least a list of the sequence of octave function calls
>>> you need to get the job done).
>>>
>>> My latest prototype with 10mm capsules was hastily measured before I
>>> left for "vacation" and the plotted results of the calibration are
>>> looking good. A re-calibration with the latest software of my first
>>> prototype which captured a full concert also sounds fairly decent.
>>>
>>> Anyway,
>>> Good luck!
>>> -- Fernando
>>>
>>>
>>>
>>> In worst case i Will use the generic calibration from sennheiser :-)
>>>>
>>>> The mechanical size of The tetraeder is about right.
>>>> Bo-Erik
>>>>
>>>>
>>>>
>>>> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>>>>
>>>> Sorry to hear of the falling-out. I have had some issues with the
>>>>> build-quality of my Brahma, which was made by Embrace Video, but
>>>>> nevertheless it remains my 'go-to' mic for choral recording.
>>>>>
>>>>> With best wishes for 2017, and for your ongoing Ambisonic microphone
>>>>> projects,
>>>>>
>>>>> Gerard
>>>>>
>>>>>
>>>>> On 02/01/2017 06:57, umashankar manthravadi wrote:
>>>>>
>>>>> This is just an announcement that Nakul Sood and Embrace video will no
>>>>>> longer be manufacturing or selling Brahma ambisonic microphones. Our
>>>>>>
>>>>> very
>>>
>>>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>>>>>> over complete technology and manufacturing protocols, 2) sign a
>>>>>> non-disclosure agreement and 3) sign a non-compete agreement. (there
>>>>>>
>>>>> were
>>>
>>>> other demands) I have always worked on Brahma as a shared project, with
>>>>>> help from many people and I have no desire to sign a non-disclosure
>>>>>> agreement.
>>>>>>
>>>>>> I had made atleast 20 Brahma microphones before this project began,
>>>>>>
>>>>> and I
>>>
>>>> will continue to make one off brahmas as demanded (I am currently
>>>>>>
>>>>> making
>>>
>>>> five second order microphones for Angelo Farina) and I am setting up
>>>>>>
>>>>> fairly
>>>
>>>> high tech processes in Bangalore where I now live (laser cut microphone
>>>>>> bodies!)
>>>>>>
>>>>>> Umashankar
>>>>>>
>>>>>>
>>>>>> -------------- next part --------------
>>>>> An HTML attachment was scrubbed...
>>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>>>>> nts/20170102/572ce57e/attachment.html>
>>>>> _______________________________________________
>>>>> Sursound mailing list
>>>>> ***@music.vt.edu
>>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
>>>>> here,
>>>>> edit account or options, view archives and so on.
>>>>>
>>>>> -------------- next part --------------
>>>> An HTML attachment was scrubbed...
>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>>>>
>>> attachments/20170103/f956a4dd/attachment.html>
>>>
>>>> _______________________________________________
>>>> Sursound mailing list
>>>> ***@music.vt.edu
>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>>>
>>> edit account or options, view archives and so on.
>>>
>>>>
>>>>
>>> _______________________________________________
>>> Sursound mailing list
>>> ***@music.vt.edu
>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>> edit account or options, view archives and so on.
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>>> attachments/20170105/7f2afed4/attachment.html>
>>> _______________________________________________
>>> Sursound mailing list
>>> ***@music.vt.edu
>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>> edit account or options, view archives and so on.
>>>
>>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>> nts/20170105/3d4d92e6/attachment.html>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>> nts/20170105/006695a8/attachment.html>
>> _______________________________________________
>> Sursound mailing list
>> ***@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
>>
> _______________________________________________
> Sursound mailing list
> ***@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
-------------- next part --------------
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umashankar manthravadi
2017-01-06 03:03:16 UTC
Permalink
Raw Message
I can send you a bunch, as front and rear IR sets. These have been processed, but I would like to see your results and see how they compare. I can send you the result filtermatrixes too, of course

umashankar

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: David McGriffy<mailto:***@mcgriffy.com>
Sent: Friday, January 6, 2017 7:25 AM
To: Surround Sound discussion group<mailto:***@music.vt.edu>
Subject: Re: [Sursound] [allowed] brahma

I recently developed a MatLab script to create calibrations based on
Angelo's method. Set up equations for each measurement's expected results,
find the LMS solution in each frequency bin, then build the resulting
filter matrix. A little engineering around the low and high frequencies
and it seems to work pretty well.

I'd also like to point out that VVEncode (alas not VVTetraVST or VVMic)
will process anyone's 4x4 matrix of filters if they are put in wav files
like Angelo and Brahma do. I also have matrix calibration processing in my
command line tool and I've done it in pure MatLab. Contact me if you want
to try this and have any questions.

I mention all this mostly because I'd be interesting in processing anyone's
custom measurements. For me this is test data for my scripts. So far I've
only run data out of one lab and with one type of
excitation/reference/etc. I'd like to make sure I'm not dependent on those
things. And I can return a working calibration, I hope.

David
VVAudio

On Thu, Jan 5, 2017 at 1:21 PM, Fernando Lopez-Lezcano <
***@ccrma.stanford.edu> wrote:

> On 01/05/2017 02:19 AM, umashankar manthravadi wrote:
>
>> I use an earthworks calibration microphone, but any good quality six mm
>> Omni microphone will be okay. Noise is not important, but flat frequency
>> response is. You could use a tetramic and take the W signal after
>> processing, but it might be overcomplicating things. Coaxial speakers sound
>> ideal, but many of them have problems. A small five inch full range, or 5
>> inch plus tweeter mounted close together, is best. I use an Adam 5 after
>> first sealing off the bass port. Choice of microphone is more important
>> than the speaker.
>>
>
> Indeed. I have an (if memory serves) emm6 "reference microphone" which is
> not very expensive but comes with its own calibration curve. Flatness is
> important as that will define how true is the frequency response of the
> calibration. For the excitation I use a single driver small speaker, so far
> it has been fine. I record is our rather small concert hall (the Stage) and
> I managed to get about 5 mSecs of useful data before the first reflection
> arrives. That seems to be enough. Completely agree with sealing the bass
> port if you have one like that, that's what Eric Benjamin recommended doing.
>
> I'll probably be offline for a few days, sorry (vacation, no internet,
> bliss)...
> Good luck!
> -- Fernando
>
>
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
>> Windows 10
>>
>> From: Bo-Erik Sandholm<mailto:***@gmail.com>
>> Sent: Thursday, January 5, 2017 3:31 PM
>> To: sursound<mailto:***@music.vt.edu>
>> Subject: Re: [Sursound] [allowed] brahma
>>
>> To get a good calibration, I expect I will need at least one
>> known/reference source or sensor?
>>
>> The reference for me will probably be my coresound Tetramic.
>>
>> I will probably use Kef eggs as speakers as they are coaxial transducers.
>> Only at low frequency will The port be offerter.
>>
>> Have I understood The basics?
>> I will probably measure outside a calibration Day orborrow a anechoic room
>> at swedish radio.
>>
>> Bo-Erik
>>
>> Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
>> ***@hotmail.com>:
>>
>> Dear fernando
>>>
>>>
>>>
>>> I forwarded your link to marc Lavallée when you first posted them. My
>>> intent is that we should have multiple compatible systems for
>>> calibrating A
>>> format mics
>>>
>>>
>>>
>>> Sent from my Windows 10 phone
>>>
>>>
>>>
>>> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
>>> Sent: 05 January 2017 00:28
>>> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
>>> ***@iol.ie<mailto:***@iol.ie>
>>> Subject: Re: [Sursound] [allowed] brahma
>>>
>>>
>>>
>>> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
>>>
>>>> Good luck in your continued effekt.
>>>>
>>>> By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
>>>> capsules.
>>>> I have not yet assembler it.
>>>> I Wonder is there any software package and description on How to create
>>>> calibration files for The mic?
>>>> I will probably have The possibility to get temporary access to a
>>>>
>>> anechoic
>>>
>>>> room.
>>>>
>>>
>>> Hi Bo-Erik,
>>> You could take a look at my project here (I posted about this a while
>>> back):
>>>
>>> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
>>> (there is mailing list with 0 posts so far, ha ha..)
>>>
>>> See paper here (been working on this for over a year):
>>> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>>>
>>> The project includes free software (open source, GPL) that runs in
>>> Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
>>> can be used directly with TetraProc (by Fons Adriansen) - or any other
>>> software that can run the filters.
>>>
>>> Just a few days ago I _finally_ managed to get the software into
>>> somewhat usable shape in that I think (and I'm pretty much wrong every
>>> time I say this, so...) it is working correctly. The calibration relies
>>> on having 16 measurements (could be 8) in the horizontal plane around
>>> the Ambisonics microphone plus one more of a calibration microphone in
>>> the same exact location. Aliki is used to capture the IRs and edit (trim
>>> and window) them. DRC (Digital Room Correction) is used to equalize the
>>> excitation speaker. Then the software I wrote processes those IRs and
>>> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
>>> a couple of pictures later...
>>>
>>> Documentation (surprise!) is mostly lacking. I hope to remedy that
>>> somewhat soon (at least a list of the sequence of octave function calls
>>> you need to get the job done).
>>>
>>> My latest prototype with 10mm capsules was hastily measured before I
>>> left for "vacation" and the plotted results of the calibration are
>>> looking good. A re-calibration with the latest software of my first
>>> prototype which captured a full concert also sounds fairly decent.
>>>
>>> Anyway,
>>> Good luck!
>>> -- Fernando
>>>
>>>
>>>
>>> In worst case i Will use the generic calibration from sennheiser :-)
>>>>
>>>> The mechanical size of The tetraeder is about right.
>>>> Bo-Erik
>>>>
>>>>
>>>>
>>>> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
>>>>
>>>> Sorry to hear of the falling-out. I have had some issues with the
>>>>> build-quality of my Brahma, which was made by Embrace Video, but
>>>>> nevertheless it remains my 'go-to' mic for choral recording.
>>>>>
>>>>> With best wishes for 2017, and for your ongoing Ambisonic microphone
>>>>> projects,
>>>>>
>>>>> Gerard
>>>>>
>>>>>
>>>>> On 02/01/2017 06:57, umashankar manthravadi wrote:
>>>>>
>>>>> This is just an announcement that Nakul Sood and Embrace video will no
>>>>>> longer be manufacturing or selling Brahma ambisonic microphones. Our
>>>>>>
>>>>> very
>>>
>>>> informal arrangement has come to an end as Nakul Sood demanded 1)I hand
>>>>>> over complete technology and manufacturing protocols, 2) sign a
>>>>>> non-disclosure agreement and 3) sign a non-compete agreement. (there
>>>>>>
>>>>> were
>>>
>>>> other demands) I have always worked on Brahma as a shared project, with
>>>>>> help from many people and I have no desire to sign a non-disclosure
>>>>>> agreement.
>>>>>>
>>>>>> I had made atleast 20 Brahma microphones before this project began,
>>>>>>
>>>>> and I
>>>
>>>> will continue to make one off brahmas as demanded (I am currently
>>>>>>
>>>>> making
>>>
>>>> five second order microphones for Angelo Farina) and I am setting up
>>>>>>
>>>>> fairly
>>>
>>>> high tech processes in Bangalore where I now live (laser cut microphone
>>>>>> bodies!)
>>>>>>
>>>>>> Umashankar
>>>>>>
>>>>>>
>>>>>> -------------- next part --------------
>>>>> An HTML attachment was scrubbed...
>>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
>>>>> nts/20170102/572ce57e/attachment.html>
>>>>> _______________________________________________
>>>>> Sursound mailing list
>>>>> ***@music.vt.edu
>>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
>>>>> here,
>>>>> edit account or options, view archives and so on.
>>>>>
>>>>> -------------- next part --------------
>>>> An HTML attachment was scrubbed...
>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>>>>
>>> attachments/20170103/f956a4dd/attachment.html>
>>>
>>>> _______________________________________________
>>>> Sursound mailing list
>>>> ***@music.vt.edu
>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>>>
>>> edit account or options, view archives and so on.
>>>
>>>>
>>>>
>>> _______________________________________________
>>> Sursound mailing list
>>> ***@music.vt.edu
>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>>> edit account or options, view archives and so on.
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/
>>> attachments/20170105/7f2afed4/attachment.html>
>>> _______________________________________________
>>> Sursound mailing list
>>> ***@music.vt.edu
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>>> edit account or options, view archives and so on.
>>>
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Bo-Erik Sandholm
2017-01-06 03:06:49 UTC
Permalink
Raw Message
I will be in contact after I am back from my Thailand holiday.

But even then I will have to concentrate a few Days in getting a
headtracker sensor to talk bluetooth.

Bo-Erik

Den 6 jan. 2017 8:55 fm skrev "David McGriffy" <***@mcgriffy.com>:

> I recently developed a MatLab script to create calibrations based on
> Angelo's method. Set up equations for each measurement's expected results,
> find the LMS solution in each frequency bin, then build the resulting
> filter matrix. A little engineering around the low and high frequencies
> and it seems to work pretty well.
>
> I'd also like to point out that VVEncode (alas not VVTetraVST or VVMic)
> will process anyone's 4x4 matrix of filters if they are put in wav files
> like Angelo and Brahma do. I also have matrix calibration processing in my
> command line tool and I've done it in pure MatLab. Contact me if you want
> to try this and have any questions.
>
> I mention all this mostly because I'd be interesting in processing anyone's
> custom measurements. For me this is test data for my scripts. So far I've
> only run data out of one lab and with one type of
> excitation/reference/etc. I'd like to make sure I'm not dependent on those
> things. And I can return a working calibration, I hope.
>
> David
> VVAudio
>
> On Thu, Jan 5, 2017 at 1:21 PM, Fernando Lopez-Lezcano <
> ***@ccrma.stanford.edu> wrote:
>
> > On 01/05/2017 02:19 AM, umashankar manthravadi wrote:
> >
> >> I use an earthworks calibration microphone, but any good quality six mm
> >> Omni microphone will be okay. Noise is not important, but flat frequency
> >> response is. You could use a tetramic and take the W signal after
> >> processing, but it might be overcomplicating things. Coaxial speakers
> sound
> >> ideal, but many of them have problems. A small five inch full range, or
> 5
> >> inch plus tweeter mounted close together, is best. I use an Adam 5 after
> >> first sealing off the bass port. Choice of microphone is more important
> >> than the speaker.
> >>
> >
> > Indeed. I have an (if memory serves) emm6 "reference microphone" which is
> > not very expensive but comes with its own calibration curve. Flatness is
> > important as that will define how true is the frequency response of the
> > calibration. For the excitation I use a single driver small speaker, so
> far
> > it has been fine. I record is our rather small concert hall (the Stage)
> and
> > I managed to get about 5 mSecs of useful data before the first reflection
> > arrives. That seems to be enough. Completely agree with sealing the bass
> > port if you have one like that, that's what Eric Benjamin recommended
> doing.
> >
> > I'll probably be offline for a few days, sorry (vacation, no internet,
> > bliss)...
> > Good luck!
> > -- Fernando
> >
> >
> >
> > Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> >> Windows 10
> >>
> >> From: Bo-Erik Sandholm<mailto:***@gmail.com>
> >> Sent: Thursday, January 5, 2017 3:31 PM
> >> To: sursound<mailto:***@music.vt.edu>
> >> Subject: Re: [Sursound] [allowed] brahma
> >>
> >> To get a good calibration, I expect I will need at least one
> >> known/reference source or sensor?
> >>
> >> The reference for me will probably be my coresound Tetramic.
> >>
> >> I will probably use Kef eggs as speakers as they are coaxial
> transducers.
> >> Only at low frequency will The port be offerter.
> >>
> >> Have I understood The basics?
> >> I will probably measure outside a calibration Day orborrow a anechoic
> room
> >> at swedish radio.
> >>
> >> Bo-Erik
> >>
> >> Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
> >> ***@hotmail.com>:
> >>
> >> Dear fernando
> >>>
> >>>
> >>>
> >>> I forwarded your link to marc Lavallée when you first posted them. My
> >>> intent is that we should have multiple compatible systems for
> >>> calibrating A
> >>> format mics
> >>>
> >>>
> >>>
> >>> Sent from my Windows 10 phone
> >>>
> >>>
> >>>
> >>> From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
> >>> Sent: 05 January 2017 00:28
> >>> To: Surround Sound discussion group<mailto:***@music.vt.edu>;
> >>> ***@iol.ie<mailto:***@iol.ie>
> >>> Subject: Re: [Sursound] [allowed] brahma
> >>>
> >>>
> >>>
> >>> On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:
> >>>
> >>>> Good luck in your continued effekt.
> >>>>
> >>>> By the way, i have accuired one of your Tetra mic 3d shapeway for 14
> mm
> >>>> capsules.
> >>>> I have not yet assembler it.
> >>>> I Wonder is there any software package and description on How to
> create
> >>>> calibration files for The mic?
> >>>> I will probably have The possibility to get temporary access to a
> >>>>
> >>> anechoic
> >>>
> >>>> room.
> >>>>
> >>>
> >>> Hi Bo-Erik,
> >>> You could take a look at my project here (I posted about this a while
> >>> back):
> >>>
> >>> https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
> >>> (there is mailing list with 0 posts so far, ha ha..)
> >>>
> >>> See paper here (been working on this for over a year):
> >>> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
> >>>
> >>> The project includes free software (open source, GPL) that runs in
> >>> Matlab and derives a calibration matrix (4x4 matrix of FIR filters)
> that
> >>> can be used directly with TetraProc (by Fons Adriansen) - or any other
> >>> software that can run the filters.
> >>>
> >>> Just a few days ago I _finally_ managed to get the software into
> >>> somewhat usable shape in that I think (and I'm pretty much wrong every
> >>> time I say this, so...) it is working correctly. The calibration relies
> >>> on having 16 measurements (could be 8) in the horizontal plane around
> >>> the Ambisonics microphone plus one more of a calibration microphone in
> >>> the same exact location. Aliki is used to capture the IRs and edit
> (trim
> >>> and window) them. DRC (Digital Room Correction) is used to equalize the
> >>> excitation speaker. Then the software I wrote processes those IRs and
> >>> outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll
> post
> >>> a couple of pictures later...
> >>>
> >>> Documentation (surprise!) is mostly lacking. I hope to remedy that
> >>> somewhat soon (at least a list of the sequence of octave function calls
> >>> you need to get the job done).
> >>>
> >>> My latest prototype with 10mm capsules was hastily measured before I
> >>> left for "vacation" and the plotted results of the calibration are
> >>> looking good. A re-calibration with the latest software of my first
> >>> prototype which captured a full concert also sounds fairly decent.
> >>>
> >>> Anyway,
> >>> Good luck!
> >>> -- Fernando
> >>>
> >>>
> >>>
> >>> In worst case i Will use the generic calibration from sennheiser :-)
> >>>>
> >>>> The mechanical size of The tetraeder is about right.
> >>>> Bo-Erik
> >>>>
> >>>>
> >>>>
> >>>> Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:
> >>>>
> >>>> Sorry to hear of the falling-out. I have had some issues with the
> >>>>> build-quality of my Brahma, which was made by Embrace Video, but
> >>>>> nevertheless it remains my 'go-to' mic for choral recording.
> >>>>>
> >>>>> With best wishes for 2017, and for your ongoing Ambisonic microphone
> >>>>> projects,
> >>>>>
> >>>>> Gerard
> >>>>>
> >>>>>
> >>>>> On 02/01/2017 06:57, umashankar manthravadi wrote:
> >>>>>
> >>>>> This is just an announcement that Nakul Sood and Embrace video will
> no
> >>>>>> longer be manufacturing or selling Brahma ambisonic microphones. Our
> >>>>>>
> >>>>> very
> >>>
> >>>> informal arrangement has come to an end as Nakul Sood demanded 1)I
> hand
> >>>>>> over complete technology and manufacturing protocols, 2) sign a
> >>>>>> non-disclosure agreement and 3) sign a non-compete agreement. (there
> >>>>>>
> >>>>> were
> >>>
> >>>> other demands) I have always worked on Brahma as a shared project,
> with
> >>>>>> help from many people and I have no desire to sign a non-disclosure
> >>>>>> agreement.
> >>>>>>
> >>>>>> I had made atleast 20 Brahma microphones before this project began,
> >>>>>>
> >>>>> and I
> >>>
> >>>> will continue to make one off brahmas as demanded (I am currently
> >>>>>>
> >>>>> making
> >>>
> >>>> five second order microphones for Angelo Farina) and I am setting up
> >>>>>>
> >>>>> fairly
> >>>
> >>>> high tech processes in Bangalore where I now live (laser cut
> microphone
> >>>>>> bodies!)
> >>>>>>
> >>>>>> Umashankar
> >>>>>>
> >>>>>>
> >>>>>> -------------- next part --------------
> >>>>> An HTML attachment was scrubbed...
> >>>>> URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme
> >>>>> nts/20170102/572ce57e/attachment.html>
> >>>>> _______________________________________________
> >>>>> Sursound mailing list
> >>>>> ***@music.vt.edu
> >>>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> >>>>> here,
> >>>>> edit account or options, view archives and so on.
> >>>>>
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> >>>>
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> >>>
> >>>> _______________________________________________
> >>>> Sursound mailing list
> >>>> ***@music.vt.edu
> >>>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> >>>>
> >>> edit account or options, view archives and so on.
> >>>
> >>>>
> >>>>
> >>> _______________________________________________
> >>> Sursound mailing list
> >>> ***@music.vt.edu
> >>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> >>> edit account or options, view archives and so on.
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> >>> ***@music.vt.edu
> >>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> >>> edit account or options, view archives and so on.
> >>>
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> >> ***@music.vt.edu
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> >>
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> >> ***@music.vt.edu
> >> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> >> edit account or options, view archives and so on.
> >>
> >>
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
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> > edit account or options, view archives and so on.
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Stefan Schreiber
2017-01-06 03:29:03 UTC
Permalink
Raw Message
Bo-Erik Sandholm wrote:

>I will be in contact after I am back from my Thailand holiday.
>
>But even then I will have to concentrate a few Days in getting a
>headtracker sensor to talk bluetooth.
>
>Bo-Erik
>
>

Hey "Bo"...

You should not read all these sursound postings and my e-mails during
your holidays...

Just enjoy the sun and the beach! ;-)

Best,

Stefan


>Den 6 jan. 2017 8:55 fm skrev "David McGriffy" <***@mcgriffy.com>:
>
>
>
>>I recently developed a MatLab script to create calibrations based on
>>Angelo's method. Set up equations for each measurement's expected results,
>>find the LMS solution in each frequency bin, then build the resulting
>>filter matrix. A little engineering around the low and high frequencies
>>and it seems to work pretty well.
>>
>>I'd also like to point out that VVEncode (alas not VVTetraVST or VVMic)
>>will process anyone's 4x4 matrix of filters if they are put in wav files
>>like Angelo and Brahma do. I also have matrix calibration processing in my
>>command line tool and I've done it in pure MatLab. Contact me if you want
>>to try this and have any questions.
>>
>>I mention all this mostly because I'd be interesting in processing anyone's
>>custom measurements. For me this is test data for my scripts. So far I've
>>only run data out of one lab and with one type of
>>excitation/reference/etc. I'd like to make sure I'm not dependent on those
>>things. And I can return a working calibration, I hope.
>>
>>David
>>VVAudio
>>
>>On Thu, Jan 5, 2017 at 1:21 PM, Fernando Lopez-Lezcano <
>>***@ccrma.stanford.edu> wrote:
>>
>>
>>
>>>On 01/05/2017 02:19 AM, umashankar manthravadi wrote:
>>>
>>>
...
Politis Archontis
2017-01-06 12:29:00 UTC
Permalink
Raw Message
Hello and a happy new year to the list,

just to mention some more resources on this topic: part of the open-source Matlab libraries I made public last year deals with this matter: deriving the matrix of filters form the microphone to the B-format signals, FOA or HOA.

The filters can be computed from a description of the array (e.g. 6 super-cardioids at some desired radius and with desired orientation, or 16 omnis on a hard sphere), or from a set of anechoic measured responses of the array. The solution can be chosen from a few different published approaches, based either on a regularized LMS (similar to Farina’s solution) or a thresholding inversion approach.

There is not extensive documentation at the moment, one needs to study the functions a bit, but you can see the results in action for the Eigenmike in these demos, along with the code that produces them:

http://research.spa.aalto.fi/projects/spharrayproc-lib/spharrayproc.html#3

where the filters are computed and evaluated based on a “theoretical” perfect Eigenmike, and then based on actual Eigenmike measurements. The evaluation is based on spatial correlation of the filtered responses, showing how similar the directivity shape across frequency is to the ideal one, (e.g. how closely the X channel resembles the perfect dipole), and level difference between the actual and the ideal component, taken as the RMS across all directions (diffuse level).

A report on these may follow soon - in the meantime if somebody’s interested to use these, let me know for additional help.

Regards,
Archontis


On 06 Jan 2017, at 03:54, David McGriffy <***@mcgriffy.com<mailto:***@mcgriffy.com>> wrote:

I recently developed a MatLab script to create calibrations based on
Angelo's method. Set up equations for each measurement's expected results,
find the LMS solution in each frequency bin, then build the resulting
filter matrix. A little engineering around the low and high frequencies
and it seems to work pretty well.

I'd also like to point out that VVEncode (alas not VVTetraVST or VVMic)
will process anyone's 4x4 matrix of filters if they are put in wav files
like Angelo and Brahma do. I also have matrix calibration processing in my
command line tool and I've done it in pure MatLab. Contact me if you want
to try this and have any questions.

I mention all this mostly because I'd be interesting in processing anyone's
custom measurements. For me this is test data for my scripts. So far I've
only run data out of one lab and with one type of
excitation/reference/etc. I'd like to make sure I'm not dependent on those
things. And I can return a working calibration, I hope.

David
VVAudio

On Thu, Jan 5, 2017 at 1:21 PM, Fernando Lopez-Lezcano <
***@ccrma.stanford.edu<mailto:***@ccrma.stanford.edu>> wrote:

On 01/05/2017 02:19 AM, umashankar manthravadi wrote:

Indeed. I have an (if memory serves) emm6 "reference microphone" which is
not very expensive but comes with its own calibration curve. Flatness is
important as that will define how true is the frequency response of the
calibration. For the excitation I use a single driver small speaker, so far
it has been fine. I record is our rather small concert hall (the Stage) and
I managed to get about 5 mSecs of useful data before the first reflection
arrives. That seems to be enough. Completely agree with sealing the bass
port if you have one like that, that's what Eric Benjamin recommended doing.

I'll probably be offline for a few days, sorry (vacation, no internet,
bliss)...
Good luck!
-- Fernando



Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
Windows 10

From: Bo-Erik Sandholm<mailto:***@gmail.com>
Sent: Thursday, January 5, 2017 3:31 PM
To: sursound<mailto:***@music.vt.edu>
Subject: Re: [Sursound] [allowed] brahma

To get a good calibration, I expect I will need at least one
known/reference source or sensor?

The reference for me will probably be my coresound Tetramic.

I will probably use Kef eggs as speakers as they are coaxial transducers.
Only at low frequency will The port be offerter.

Have I understood The basics?
I will probably measure outside a calibration Day orborrow a anechoic room
at swedish radio.

Bo-Erik

Den 5 jan. 2017 11:53 fm skrev "umashankar manthravadi" <
***@hotmail.com<mailto:***@hotmail.com>>:

Dear fernando



I forwarded your link to marc Lavallée when you first posted them. My
intent is that we should have multiple compatible systems for
calibrating A
format mics



Sent from my Windows 10 phone



From: Fernando Lopez-Lezcano<mailto:***@ccrma.Stanford.EDU>
Sent: 05 January 2017 00:28
To: Surround Sound discussion group<mailto:***@music.vt.edu>;
***@iol.ie<mailto:***@iol.ie><mailto:***@iol.ie>
Subject: Re: [Sursound] [allowed] brahma



On 01/02/2017 09:59 PM, Bo-Erik Sandholm wrote:

Good luck in your continued effekt.

By the way, i have accuired one of your Tetra mic 3d shapeway for 14 mm
capsules.
I have not yet assembler it.
I Wonder is there any software package and description on How to create
calibration files for The mic?
I will probably have The possibility to get temporary access to a

anechoic

room.


Hi Bo-Erik,
You could take a look at my project here (I posted about this a while
back):

https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
(there is mailing list with 0 posts so far, ha ha..)

See paper here (been working on this for over a year):
https://ccrma.stanford.edu/~nando/publications/sphear.pdf

The project includes free software (open source, GPL) that runs in
Matlab and derives a calibration matrix (4x4 matrix of FIR filters) that
can be used directly with TetraProc (by Fons Adriansen) - or any other
software that can run the filters.

Just a few days ago I _finally_ managed to get the software into
somewhat usable shape in that I think (and I'm pretty much wrong every
time I say this, so...) it is working correctly. The calibration relies
on having 16 measurements (could be 8) in the horizontal plane around
the Ambisonics microphone plus one more of a calibration microphone in
the same exact location. Aliki is used to capture the IRs and edit (trim
and window) them. DRC (Digital Room Correction) is used to equalize the
excitation speaker. Then the software I wrote processes those IRs and
outputs a 4x4 matrix of filters. Many parameters can be tuned. I'll post
a couple of pictures later...

Documentation (surprise!) is mostly lacking. I hope to remedy that
somewhat soon (at least a list of the sequence of octave function calls
you need to get the job done).

My latest prototype with 10mm capsules was hastily measured before I
left for "vacation" and the plotted results of the calibration are
looking good. A re-calibration with the latest software of my first
prototype which captured a full concert also sounds fairly decent.

Anyway,
Good luck!
-- Fernando



In worst case i Will use the generic calibration from sennheiser :-)

The mechanical size of The tetraeder is about right.
Bo-Erik



Den 2 jan. 2017 9:01 em skrev "Gerard Lardner" <***@iol.ie>:

Sorry to hear of the falling-out. I have had some issues with the
build-quality of my Brahma, which was made by Embrace Video, but
nevertheless it remains my 'go-to' mic for choral recording.

With best wishes for 2017, and for your ongoing Ambisonic microphone
projects,

Gerard


On 02/01/2017 06:57, umashankar manthravadi wrote:

This is just an announcement that Nakul Sood and Embrace video will no
longer be manufacturing or selling Brahma ambisonic microphones. Our

very

informal arrangement has come to an end as Nakul Sood demanded 1)I hand
over complete technology and manufacturing protocols, 2) sign a
non-disclosure agreement and 3) sign a non-compete agreement. (there

were

other demands) I have always worked on Brahma as a shared project, with
help from many people and I have no desire to sign a non-disclosure
agreement.

I had made atleast 20 Brahma microphones before this project began,

and I

will continue to make one off brahmas as demanded (I am currently

making

five second order microphones for Angelo Farina) and I am setting up

fairly

high tech processes in Bangalore where I now live (laser cut microphone
bodies!)

Umashankar


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