brahma on kickstarter

[umashankar]

everybody take a look http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone

umashankar

[Peter Larsen[_3_]]

umashankar wrote:

> everybody take a look
> http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone

Yes, looks like spam, is spam, but nonetheless, interesting enough to go
take a look at.

> umashankar

Kind regards

Peter Larsen

[umashankar]

On Wednesday, October 30, 2013 8:13:03 AM UTC+5:30, umashankar wrote:
> everybody take a look http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone
>
>
>
> umashankar

oops. I did not intend to spam. umashankar

[Peter Larsen[_3_]]

umashankar wrote:

> On Wednesday, October 30, 2013 8:13:03 AM UTC+5:30, umashankar wrote:
>> everybody take a look

>> http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone

>> umashankar

> oops. I did not intend to spam. umashankar

Not to worry, actually quite relevant in the context of a recent discussion,
I had certainly appreciated your potential input and ocmments to it.
Marketing via media presence, be it here or on FB is - to say it very
tersely - very much about being present and getting known.

Kind regards

Peter Larsen

[hank alrich]

Peter Larsen > wrote:

> umashankar wrote:
>
> > On Wednesday, October 30, 2013 8:13:03 AM UTC+5:30, umashankar wrote:
> >> everybody take a look
>
> >>
> http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonic
> s-microphone
>
> >> umashankar
>
> > oops. I did not intend to spam. umashankar
>
> Not to worry, actually quite relevant in the context of a recent discussion,
> I had certainly appreciated your potential input and ocmments to it.
> Marketing via media presence, be it here or on FB is - to say it very
> tersely - very much about being present and getting known.

I haven't seen this project before. Have you an idea how this compares
with Core-Sound's Tetramic?

--
shut up and play your guitar * HankAlrich.Com
HankandShaidriMusic.Com
YouTube.Com/WalkinayMusic

[Peter Larsen[_3_]]

hank alrich wrote:

>> http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonic
>> s-microphone

> I haven't seen this project before. Have you an idea how this compares
> with Core-Sound's Tetramic?

Ignoramus me, I don't know what the Tetramic is. I didn't find as many hard
data as I would have liked on the brahma site.

Kind regards

Peter Larsen

[William Sommerwerck]

It would be nice to know something about the capsules used in the Core and
Brahma mics.

I made Ambisonic recordings with both discrete mics and the SoundField. In
principle, A- or B-format recording gives unlimited control over single-point
miking, for stereo or surround.

[hank alrich]

Peter Larsen > wrote:

> hank alrich wrote:
>
> >> http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonic
> >> s-microphone
>
> > I haven't seen this project before. Have you an idea how this compares
> > with Core-Sound's Tetramic?
>
> Ignoramus me, I don't know what the Tetramic is. I didn't find as many hard
> data as I would have liked on the brahma site.

http://core-sound.com/TetraMic/1.php

--
shut up and play your guitar * HankAlrich.Com
HankandShaidriMusic.Com
YouTube.Com/WalkinayMusic

[Scott Dorsey]

William Sommerwerck > wrote:
>It would be nice to know something about the capsules used in the Core and
>Brahma mics.

I know something about the ones used in the Core mikes. They aren't the
best but they aren't the worst, and they hand-select them for matching.
But, they are using cardioids rather than figure-8s so the compound pattern
isn't going to be as good.

The Tetramic is not up to the quality of the Calrecs, but by the same token
it is a WHOLE lot cheaper and it is an excellent way to get into ambisonic
recording at a reasonable starting price.

For broadcast folks and for fixed installed applications, the ability to
control the stereo image in the process of bumping down the A-format input
to stereo is a huge advantage of the ambisonic stuff, even if you are just
going to 2-channel stereo out.

I don't know what is in the Brahma mike; looking at the picture on the
website I don't recognize the capsules and they don't have any side vents
so it's possible they are somebody's figure-8 electrets. Would be interesting
to see how they work.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[umashankar]

On Wednesday, October 30, 2013 8:13:03 AM UTC+5:30, umashankar wrote:
> everybody take a look http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone
>
>
>
> umashankar

the capsules used are TSB 140s. These are 14 mm diameter electret capsules with built in FETs and outputs from both drain and source. The capsules used by Coresound are smaller. The outer body is 12 mm, but it more like a whole mic than a capsule so the diaphgram would be much smaller.

I believe there is a few db difference in sensitivity between the two capsules, based on manufacturer's specifications. (the tetramic has lowish output.

[William Sommerwerck]

"Scott Dorsey" wrote in message ...
William Sommerwerck > wrote:

>> It would be nice to know something about the capsules
>> used in the Core and Brahma mics.

> I know something about the ones used in the Core mikes.
> They aren't the best but they aren't the worst, and they
> hand-select them for matching. But, they are using cardioids
> rather than figure-8s so the compound pattern isn't going to
> be as good.

Whoops. You can't produce B-format from figure-8 mics. That is, you can't
produce the mono first-order signal (W) from signals which have no first-order
component. You have to have cardioids.

Of course, it would be desirable if the capsules had matched patterns (as well
as frequency response).


> The Tetramic is not up to the quality of the Calrecs, but by the
> same token it is a WHOLE lot cheaper and it is an excellent
> way to get into ambisonic recording at a reasonable starting price.

I owned an "official" SoundField, and was not pleased with the sound quality.
If the Core and Brahma mics are inferior...

[Tom McCreadie]

Scott Dorsey wrote:

>I know something about the ones used in the Core mikes. They aren't the
>best but they aren't the worst, and they hand-select them for matching.
>But, they are using cardioids rather than figure-8s so the compound pattern
>isn't going to be as good.
>
>The Tetramic is not up to the quality of the Calrecs, but by the same token
>it is a WHOLE lot cheaper and it is an excellent way to get into ambisonic
>recording at a reasonable starting price.

You've got me a bit confused here, Scott, for I recall reading reliable reports
that the (tetrahedrally-aligned) capsules in the Calrec Soundfield are of a wide
cardioid pattern.

Besides, whenever Fig-8's were involved, I thought the 3-D coverage was usually
taken care of by employing an array of 3 Fig-8's along the X,Y,Z axes, plus an
omni - rather than with 4 tetrahedrally-aligned Fig-8's.

[Scott Dorsey]

Tom McCreadie > wrote:
>You've got me a bit confused here, Scott, for I recall reading reliable reports
>that the (tetrahedrally-aligned) capsules in the Calrec Soundfield are of a wide
>cardioid pattern.

Right. This creates an "A-format" output, which goes into some sum and
difference logic to create the "B-format" signals which are three pure
velocity signals and one pressure signal. That is, they are synthesizing
figure-8 and omni mikes from the cardioid capsules.

>Besides, whenever Fig-8's were involved, I thought the 3-D coverage was usually
>taken care of by employing an array of 3 Fig-8's along the X,Y,Z axes, plus an
>omni - rather than with 4 tetrahedrally-aligned Fig-8's.

Yes, precisely. This is a better way of doing it than the Core Sound or
Calrec folks have chosen, in theory. The problem is that in practice putting
all those mikes together causes them to interfere with the patterns of one
another. There are various ways to deal with this using either of the two
configurations.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Tom McCreadie]

On 1 Nov 2013 21:44:03 -0400, (Scott Dorsey) wrote:

>Tom McCreadie > wrote:
>>You've got me a bit confused here, Scott, for I recall reading reliable reports
>>that the (tetrahedrally-aligned) capsules in the Calrec Soundfield are of a wide
>>cardioid pattern.
>
>Right. This creates an "A-format" output, which goes into some sum and
>difference logic to create the "B-format" signals which are three pure
>velocity signals and one pressure signal. That is, they are synthesizing
>figure-8 and omni mikes from the cardioid capsules.
>
Thanks for the clarification. As I suspected, I'd misread your post: inferred
that you were saying that the Coresound mics used cardioid physical capsules -
in contrast to the Soundield, that used Fig-8 capsules.

I've since unearthed my info* on the Calrec's subcardioid pattern:

V = 0.667 + 0.334.cos(theta)

* Kenneth Farrar, 1977, Soundfield Microphone, AMS Calrec technical paper.

[Scott Dorsey]

Tom McCreadie > wrote:
>>
>Thanks for the clarification. As I suspected, I'd misread your post: inferred
>that you were saying that the Coresound mics used cardioid physical capsules -
>in contrast to the Soundield, that used Fig-8 capsules.

I wasn't very clear.

What is interesting is the size of the capsules used in the Coresound mikes
vs. the Soundfield. The smaller capsules have two advantages, first you
have less "shadowing" where one mike influences the pattern of the other,
and secondly you can get them closer so the capsules are closer to being
coincident at higher frequencies.

I had looked at the Brahma photo on the web and saw capsules with no
side venting, so I assumed they were figure-8 capsules (since it would
be impractical for them to be omnis). However, upon clarification from
the original poster saying they were Transsound TS-140 capsules, I looked
those up and they do appear to sell a back-vented cardioid still.

Looking at the picture of the Brahma, it looks like they are very close
together for improved coincidence, and I worry that the resulting shadowing
may affect the pattern. I'm curious if the backvented capsule design makes
that better or worse and I don't know at what point it becomes a problem.

I do know that Calrec spent a lot of time balancing the two issues.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[umashankar]

On Wednesday, October 30, 2013 8:13:03 AM UTC+5:30, umashankar wrote:
> everybody take a look http://www.kickstarter.com/projects/1569945514/brahma-affordable-ambisonics-microphone
>
>
>
> umashankar

I have a secret sauce for the back venting issue and the capsules are almost as close as a 14 mm X 5 mm cylinder can get - the radius measures out at 15 mm, and it is probably closer if I take diaphragm center to diaphragm center measure. we are in the process of calibrating and will post complete data which will result from this process.

umashankar