Topic: Makers of Figure 8 mics/capsules

[page]

I'm primarily interesting in capsules, especially ones that can be purchased and flown in an active style, but any info is appreciated.

I know that Neumann and Schoeps make 8 caps *and* have active systems of some sort, while Milab and Busman make mics that can send an 8 signal but that comes out of a full body (usually switchable at that). What else is there?

This is what provoked my question: 
http://taperssection.com/index.php/topic,115533.msg1546249.html#msg1546249

[OOK]

MBHO.......................

[vanark]

I recently saw an Oktava Figure 8 capsule for the MK-012 bodies.

[noahbickart]

akg ck94 for the Blue line series.

-Noah

[page]

MBHO.......................

akg ck94 for the Blue line series.

I'd forgotten both of those  (especially MBHO). Thanks!

I recently saw an Oktava Figure 8 capsule for the MK-012 bodies.

heh, the ghetto 8, fairs fair though, I asked. Thanks.

[OOK]

MBHO.......................

Best bang for the buck IMO....

[John Willett]

Sennheiser MKH 30.

As far as I know most people make figure-8 mics from two cardioid capsules, back-to-back.

There are only 3 condenser fig-8 mics that are real fig-8s with a single diaphragm:-

Sennheiser MKH 30 - fully symmetrical, electrically and acoustically.
Neumann AK 20 - acoustically symmetrical
Schoeps - not symmetrical, the rear lobe is slightly different at the gighest frequencies.

I hope this helps.

[DSatz]

John, the Schoeps MK 8/CCM 8 is definitely symmetrical. I believe you may be referring to the published polar diagram, which shows a ca. 2 dB decrease in relative response at 16 kHz from 180 degrees. It is strange to me that they use this curve; I hope to find out why. But the capsule's internal physical construction is entirely symmetrical--in principle exactly as the Neumann AK 20's is, with one "active" backplate plus an acoustically identical "backplate" on the other side of the diaphragm which is not active electrically.

--best regards

[John Willett]

John, the Schoeps MK 8/CCM 8 is definitely symmetrical. I believe you may be referring to the published polar diagram, which shows a ca. 2 dB decrease in relative response at 16 kHz from 180 degrees. It is strange to me that they use this curve; I hope to find out why. But the capsule's internal physical construction is entirely symmetrical--in principle exactly as the Neumann AK 20's is, with one "active" backplate plus an acoustically identical "backplate" on the other side of the diaphragm which is not active electrically.

Thanks for letting me know.

Yes, I was going from the published curve which clearly shows a rear attenuation at high frequencies.

I had also heard that it did not have a front plate.

Unless it used to be as I said and they have now changed it and forgotten to update the polar-pattern.

Please let me know if you find out as I do not like to give incorrect infrmation.

Thanks.

[DSatz]

John, all single-pattern figure-8 capsules and microphones that Schoeps has ever made have followed a symmetrical, single-diaphragm design. Their three-pattern capsules (which, while using only a single diaphragm, include a figure-8 setting) are perhaps a different story in a way: During the first half of the 1960s, Schoeps used a true push-pull design for this type of capsule.

But then they changed over to the design which they still use today, which is acoustically symmetrical but not push-pull. So with tongue in cheek, one could perhaps say that they went from a "Sennheiser-like" approach (the CMT 26 even used an RF amplifier circuit!) to a "Neumann-like" approach--though it was decades before Sennheiser or Neumann made any such microphones ...

--best regards

[page]

During the first half of the 1960s, Schoeps used a true push-pull design for this type of capsule. But then they changed over to the design which they still use today, which is acoustically symmetrical but not push-pull.

Whats the real-world difference between the two that would cause them to make the shift? easier production or is there something tangible to the end-user? Just curious. Thanks.

[F.O.Bean]

what about the MBHO KA800A Its a side-address capsule just like the MK8 is, isnt it Wouldnt it technically be a symmetrical capsule as well The polar pattern I have seen of it was def symmetrical......I LOST all of my bookmarks when I reformatted tho I forgot to save that last bookmark

Anyway......I'd love to know the answers to those.....

[DSatz]

page, first I should "disclaim" that I've done a lot of translating and editorial consulting for Schoeps on a freelance basis, but I have no particular formal relationship with the company and am certainly not a spokesperson for them. My views are pretty much my own (or at least I like to imagine that they are).

That said: Some time back I asked the same question of two engineers at Schoeps, but they aren't the people who made the decision 40+ years ago. So I can only give you my impression of their impression, or what they chose to share with me--which is basically that the push-pull capsule design brought additional complexity without any notable sonic benefit. And I don't know whether it's a coincidence or not, but the capsules which used this design are among the few types that Schoeps won't accept for repair any more.

In March, 1981 two leading engineers from Sennheiser presented an AES paper which set forth the theory behind push-pull capsule design. The objective findings of that paper aren't in any dispute that I know of: A push-pull capsule can have lower distortion than an otherwise comparable design that isn't push-pull. But the push-pull approach, by itself, is no guarantee of either a low distortion figure OR of a good-sounding microphone. It isn't clear to what degree the distortions canceled by a push-pull design are ever audible in capsules that don't use the technique. The 1981 paper didn't discuss audibility, and I for one have seen no further papers on this topic. Opinions, sure--but facts, not so much. And this seems a mite strange to me.

I wonder whether Sennheiser engineers ever made comparison recordings while they were developing their capsule designs back then. They could fairly easily have made identical microphones with and without the push-pull technique, and then recorded the same music with identically-placed microphones of both kinds.

If that were being done today, they could even make stereo recordings with both kinds of microphone on a four-track digital recorder, then subtract the one recording from the other to hear just the difference (presumably the distortion that the push-pull design cancels out). That's something that I'd really want to hear before forming too strong an opinion either way about this.

--best regards

[John Willett]

page, first I should "disclaim" that I've done a lot of translating and editorial consulting for Schoeps on a freelance basis, but I have no particular formal relationship with the company and am certainly not a spokesperson for them. My views are pretty much my own (or at least I like to imagine that they are).

That said: Some time back I asked the same question of two engineers at Schoeps, but they aren't the people who made the decision 40+ years ago. So I can only give you my impression of their impression, or what they chose to share with me--which is basically that the push-pull capsule design brought additional complexity without any notable sonic benefit. And I don't know whether it's a coincidence or not, but the capsules which used this design are among the few types that Schoeps won't accept for repair any more.

In March, 1981 two leading engineers from Sennheiser presented an AES paper which set forth the theory behind push-pull capsule design. The objective findings of that paper aren't in any dispute that I know of: A push-pull capsule can have lower distortion than an otherwise comparable design that isn't push-pull. But the push-pull approach, by itself, is no guarantee of either a low distortion figure OR of a good-sounding microphone. It isn't clear to what degree the distortions canceled by a push-pull design are ever audible in capsules that don't use the technique. The 1981 paper didn't discuss audibility, and I for one have seen no further papers on this topic. Opinions, sure--but facts, not so much. And this seems a mite strange to me.

I wonder whether Sennheiser engineers ever made comparison recordings while they were developing their capsule designs back then. They could fairly easily have made identical microphones with and without the push-pull technique, and then recorded the same music with identically-placed microphones of both kinds.

If that were being done today, they could even make stereo recordings with both kinds of microphone on a four-track digital recorder, then subtract the one recording from the other to hear just the difference (presumably the distortion that the push-pull design cancels out). That's something that I'd really want to hear before forming too strong an opinion either way about this.

When I talked to the Sennheiser designer of the push-pull capsule he did tell me that it was much easier to do with an RF condenser than an AF - due to the fact that the RF capsule is low impedance and the AF very high impedance with the added problem of having an active backplate in the front of the diaphragm.

Did you ever hear the Sennheiser demo. CD that they did in 1985 when they launched the MKH 40?

It had examples of IM-distortion of the MKH 40, a top quality LDC and a top quality SDC.

If you didn't and want to, I'm happy to send you a copy.

The CD was deleted many years ago, but I have a copy on MY PC - I replaced the music samples with stuff I recorded myself and documented the microphones and positioning.

[dbindc]

I "took delivery" on a MBHO KA800 figure eight pattern capsule in September after "buying it" in April.  It came with absolutely no documentation. It's definitely a single diaphragm and  I'm assuming it's a symmetrical design as most other MBHO products I have seem closely related to Schoeps microphone designs.  Does anyone know for sure or have a link to any info on the capsule like a polar pattern graph?  Doesn't seem to be one on their website.

That said, I'm very happy with it based on the few MS recordings I've done - especially running center stage lip about waist high.  Awesome stereo image and picks up way more vocals than any other stereo pattern I have run on stage.  Lately I've been pairing it with a DPA 4022 for the mid rather than a Ho card.  Gives it better overall bass response esp picking up the kick drum from a distance.  I'm loving my foray into MS recording.  From further back though seems I'm better of running cards or hypers.

[page]

Does anyone know for sure or have a link to any info on the capsule like a polar pattern graph?  Doesn't seem to be one on their website.

http://www.amptec.de/test/Alle%20Seiten/MBHO/MBHO%20capsules.html

The PDFs don't work, but the images are there.

[F.O.Bean]

I "took delivery" on a MBHO KA800 figure eight pattern capsule in September after "buying it" in April.  It came with absolutely no documentation. It's definitely a single diaphragm and  I'm assuming it's a symmetrical design as most other MBHO products I have seem closely related to Schoeps microphone designs.  Does anyone know for sure or have a link to any info on the capsule like a polar pattern graph?  Doesn't seem to be one on their website.

That said, I'm very happy with it based on the few MS recordings I've done - especially running center stage lip about waist high.  Awesome stereo image and picks up way more vocals than any other stereo pattern I have run on stage.  Lately I've been pairing it with a DPA 4022 for the mid rather than a Ho card.  Gives it better overall bass response esp picking up the kick drum from a distance.  I'm loving my foray into MS recording.  From further back though seems I'm better of running cards or hypers.

Thanks for the response

[Gutbucket]

Does anyone know for sure or have a link to any info on the capsule like a polar pattern graph?  Doesn't seem to be one on their website.

http://www.amptec.de/test/Alle%20Seiten/MBHO/MBHO%20capsules.html

The PDFs don't work, but the images are there.

MBHO KA800-

The photo sure makes it look like a stereo mic, do two individual capsules somehow link together or is that photo incorrect?


Granted the print is small, but I'm having a hard time reconciling their polar plot and on-axis response graph-

[page]

The photo sure makes it look like a stereo mic, do two individual capsules somehow link together or is that photo incorrect?

I think it was taken while sitting on a mirror.

[boojum]

Not a mirror image.  There is engraving on the upper module which is not on the lower, assuming the "mirror" is at the horizontal seam.

[F.O.Bean]

so it IS a side-address capsule, right? Meaning that the 0* marking needs to be pointing TOWARDS the soundsource, correct?

[dbindc]

Gutbucket is on target.  This photo appears to be two KA 800 capsules attached in the manner of a stereo ribbon mic like a Royer.  My KA800 capsule looks like just the top half.  I've been pointing the end in the direction of the cardiod mic and aligning the 0 degree mark to the right side as close to perpendicular as possible.

[page]

Gutbucket is on target.  This photo appears to be two KA 800 capsules attached in the manner of a stereo ribbon mic like a Royer.  My KA800 capsule looks like just the top half.  I've been pointing the end in the direction of the cardiod mic and aligning the 0 degree mark to the right side as close to perpendicular as possible.

thanks, I missed the lack of the angle which would have indicated the mirror.

[F.O.Bean]

Gutbucket is on target.  This photo appears to be two KA 800 capsules attached in the manner of a stereo ribbon mic like a Royer.  My KA800 capsule looks like just the top half.  I've been pointing the end in the direction of the cardiod mic and aligning the 0 degree mark to the right side as close to perpendicular as possible.

Awesome So the "top" of the capsule points towards the soundsource, while the 0* marking points towards the right, perpendicular to the soundsource Thanks brah!!!

I couldve sworn that the 0* marking was always supposed to be to the left side tho

[DSatz]

Gutbucket, hoping I don't sound too much like the Borg here, but trying to "reconcile" a frequency response graph with a polar response graph is futile. The curves in a polar diagram are independent of the microphone's on-axis frequency response.

The purpose of a polar diagram is to let you see the similarity or note any anomalies in directional response in the different frequency ranges that the microphone picks up. For each frequency that's displayed in the polar diagram, the actual 0-degree sensitivity of the microphone at that frequency is not taken into consideration. Instead, the polar diagram shows it as "0 dB," and it becomes the reference point for the rest of the curve at that one frequency. This process is then repeated for each frequency on the list.

If they didn't do that, some of the curves might go well beyond the circle (think of a diffuse-field omni microphone whose response is up 6 dB at 8 kHz) while others would be tiny (think of a speech cardioid microphone which is down 12 dB at 50 Hz). If you wanted to make a graph like that, you certainly could, by taking the frequency response curve, looking up the 0-degree sensitivity at each of the relevant frequencies, and then applying those values as "multipliers" to the size of the polar graph for that frequency.

But in the normal way of drawing a polar diagram, the frequency response is specifically excluded as a factor because that information is already contained in the frequency response graph--so it would be redundant, and for microphones with non-flat frequency response, kind of messy looking.

As a test, see whether this way of putting things now makes sense to you: The ability to "reconcile" the two kinds of graph would only be an indication of whether the microphone has flat response or not--and the frequency response graph already gives you that information, so the polar graph doesn't.

--best regards

P.S. (added later): Looking back at your message, I see that MBHO apparently scaled each of the individual polar curves by some seemingly arbitrary factor. I agree that this is distracting, but actually in principle, it's "no more artificial" than the usual way is, where each individual curve starts at 0 dB for 0 degrees. I assume it's just their way of trying to present the different shapes without having to draw lines to label them.

[Gutbucket]

Information assimilated.

Thanks for the clarification, the scaled response curves of the polar plot (not normalized to 0db at 0 degrees) is what threw me.  Since the polar plot response curves didn't all line up at 0 degrees like I've come to expect of most polar plots with your guidance, it seemed to me that they'd plotted the diagram using the absolute frequency response values.  If that was the case, the data from a vertical 'slice' of polar plot at 0 degrees should match the frequency response graph.  That's how I thought all polar plots worked until you previously instructed me as to how the typical polar plot is displayed (response normalized to 0db at 0 degrees).

When I saw the plot for this capsule I thought, "Hey, that's showing the absolute response on the polar plot like I originally imagined they worked." Yet that doesn't appear to be the case either since the db values for 0 degrees don't match the frequency response graph.

Would it be safe to summarize the information displayed on a polar plot in the following way? - A 'typical' polar response plot shows the change in response, not the absolute response for each angle in the horizontal plane?

Thanks again for your help in understanding this.

[page]

Gutbucket is on target.  This photo appears to be two KA 800 capsules attached in the manner of a stereo ribbon mic like a Royer.  My KA800 capsule looks like just the top half.  I've been pointing the end in the direction of the cardiod mic and aligning the 0 degree mark to the right side as close to perpendicular as possible.

Awesome So the "top" of the capsule points towards the soundsource, while the 0* marking points towards the right, perpendicular to the soundsource Thanks brah!!!

I couldve sworn that the 0* marking was always supposed to be to the left side tho

Well, it depends on what your using it for, it's a "side address" cap, I'm relatively sure of that (almost all fig8s are), but where you point the positive lobe depends on what your doing.

If you've got one handy, set up an MS setup (both "pointed" forward, so your card toward 0 and the fig8 toward 90. Snap your fingers a couple of times at 90, 0, and 270. Then do the MS decode in post and see what happens what you get. If you remember or take notes on what side and what was there when you did the first snap, then you'll see what the positive lobe is.

[Len Moskowitz (Core Sound)]

I'm primarily interesting in capsules, especially ones that can be purchased and flown in an active style, but any info is appreciated.

Tetrahedral ambisonic mics, like our TetraMic and the mics from SoundField Ltd., can do the job well.

With no exaggeration, our TetraMic is probably one of the finest figure-8 mics in the world.  It also is one of the finest Blumlein arrays in the world.  And M/S.  And surround.

(Yes, you read that correctly: TetraMic can function as single mic, a pair of mics, or as many coincident mics as you desire.)

[F.O.Bean]

Gutbucket is on target.  This photo appears to be two KA 800 capsules attached in the manner of a stereo ribbon mic like a Royer.  My KA800 capsule looks like just the top half.  I've been pointing the end in the direction of the cardiod mic and aligning the 0 degree mark to the right side as close to perpendicular as possible.

Awesome So the "top" of the capsule points towards the soundsource, while the 0* marking points towards the right, perpendicular to the soundsource Thanks brah!!!

I couldve sworn that the 0* marking was always supposed to be to the left side tho

Well, it depends on what your using it for, it's a "side address" cap, I'm relatively sure of that (almost all fig8s are), but where you point the positive lobe depends on what your doing.

If you've got one handy, set up an MS setup (both "pointed" forward, so your card toward 0 and the fig8 toward 90. Snap your fingers a couple of times at 90, 0, and 270. Then do the MS decode in post and see what happens what you get. If you remember or take notes on what side and what was there when you did the first snap, then you'll see what the positive lobe is.

Isnt 0* supposed to be on one particular side tho? Like left or right?

[page]

Isnt 0* supposed to be on one particular side tho? Like left or right?

Each mic maker could intend for that sign to mean something different with orientation interpretation. I'm not sure that they would, and I personally would anticipate it to be the left side (or positive lobe is a more accurate term I guess), but the easiest way is to check it out.

[F.O.Bean]

Isnt 0* supposed to be on one particular side tho? Like left or right?

Each mic maker could intend for that sign to mean something different with orientation interpretation. I'm not sure that they would, and I personally would anticipate it to be the left side (or positive lobe is a more accurate term I guess), but the easiest way is to check it out.

Thanks ALOT bro!

[John Willett]

I'm primarily interesting in capsules, especially ones that can be purchased and flown in an active style, but any info is appreciated.

Tetrahedral ambisonic mics, like our TetraMic and the mics from SoundField Ltd., can do the job well.

With no exaggeration, our TetraMic is probably one of the finest figure-8 mics in the world.  It also is one of the finest Blumlein arrays in the world.  And M/S.  And surround.

(Yes, you read that correctly: TetraMic can function as single mic, a pair of mics, or as many coincident mics as you desire.)

Just been looking at the website on this.

It seems that the capsules are cardioid - the original soundfield used hypo-cardioid (ie: wide-cardioid).

What is the reason for this?  Was it just to get around patents, or was the software written specially for the cardioid pattern?

Also, I could not see capsule frequency response curves and polar-patterns on the site.  Are they there and I just missed them?

Just curious (at the moment).

[Gutbucket]

I'm curious about the tetramic too.  I think the original soundfield patents are expired and as I understand it, the software was written specifically for the response of the particular capsule used and the physical arrangement of the four.  As for choice of pattern, cardioid capsules are easily available and inexpensive.  I'd think they'd be the natural choice, especially since the omni and figure 8 compontents of the cardioid pattern have the same relative sensitivity.

I've never used an ambisonic system and I'm by no stretch of the imagination an ambisonic expert, but I imagine any pattern that falls somewere between omni and figure-8 could work in the array, as long as the weighting of the matrix was to be changed to match.  A pattern other than cardioid would need the balance beween the omni and the figure-8 components adjusted (in the software in this case). Patterns to one extreme or the other would be less optimal as they would eat up the available headroom dynamic range if they needed large scaling factors. Using hypo-cards, you'd get more omni component, and would have to scale that down to match the level of the figure-8. Didn't the original ambisonic equations call for scaling the W component by .707? Could that have been to compensate for the extra omni content in the A format using hypo-cardioids?

I may be completely off base here and appreciate clarification by those who know.  Tell us more about your interesting mic, Len.

[Kewl]

It seems that the capsules are cardioid - the original soundfield used hypo-cardioid (ie: wide-cardioid). What is the reason for this?  Was it just to get around patents, or was the software written specially for the cardioid pattern?

The patents for the tetrahedral array have been expired for a while: this is why we saw the AGM tetrahedral array (with DPA caps) in the 90s.

If they could have used cardioids on the original SoundField, they would have: use of cardioids will provide the best S/N ratio in the B-Format channels.

- Daniel

[fotoralf.be]

Does anone here know anything about the fig-8 capsules in the various Sony MS stereo mics, i.e. ECM 909, 959 etc.?

Ralf

[darby]

Does anone here know anything about the fig-8 capsules in the various Sony MS stereo mics, i.e. ECM 909, 959 etc.?

Ralf

they are 2 cardioid caps back to back for the figure 8
plus another cardioid for the mid... if I'm not mistaken

[fotoralf.be]

they are 2 cardioid caps back to back for the figure 8

Definitely not in the 909. One capsule pointing forward and one looking sideways.

Ralf

[Len Moskowitz (Core Sound)]

Also, I could not see capsule frequency response curves and polar-patterns on the site.  Are they there and I just missed them?

You can get a sense of TetraMic's polar patterns and frequency response curves from Fons Adriaenson's data here:

http://www.kokkinizita.net/linuxaudio/tetra-pict.html

TetraMic is never used as individual capsules.  The decoded polar patterns and frequency responses have very little relationship to the individual capsule patterns and frequency responses.

Have a look at this short description of how TetraMic works.  I hope it will help.

http://taperssection.com/index.php?topic=111984.0

Here's a nice recording done with TetraMic and an unnamed mic pre/ADC:

http://www.ambisonia.com/Members/soundmanjohn/ambisonicfile.2008-04-14.9034658665

Here's a link to an excerpt of that recording decoded to Blumlein (66 MB):

http://www.core-sound.com/Orfeo-Blumlein-second-movement.wav

[Gutbucket]

Thanks for the links.

[darby]

they are 2 cardioid caps back to back for the figure 8

Definitely not in the 909. One capsule pointing forward and one looking sideways.

Ralf

http://taperssection.com/index.php/topic,116512.0.html