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DPA 2006 twin diaphragm design: not sure I get this
Old 22nd December 2014
  #1
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DPA 2006 twin diaphragm design: not sure I get this

DPA's 2006 series microphones have two 1/4" diaphragms in place of the one 1/2" diaphragm of the 400x series. From DPA:

Quote:
In a 2006 capsule two opposite facing miniature capsules are custom re-built into a double diaphragm, one-capsule composition. This combines the advantages of small capsules (fast impulse response and large frequency bandwidth) with lower inherent noise achieved from a larger diaphragm area.
Say what? I'm not sure I get this. The two capsules are facing opposite (front/back or side/side?) one on top or next to the other, or just back to back? And this is true of both the omni and cardioid versions, the latter of which uses an interference tube to make it cardioid.

Now, this yields the same amount of diaphragm real estate as a 1/2" diaphragm, and that's how it attains the same low noise spec. But what are they, sort of just wired together in series? And why hasn't anyone else tried this, including DIYers?

I'm at a loss for a headscratcher emoji. Can anyone shed any light on this; I guess we are all reading the same texts on the internet, but I'm intrigued by this.


DPA Microphones :: Products

Darth Fader reviews DPA (Danish Pro Audio) 2006C and 2011C Microphones (mics). | L2PNet.com
Old 22nd December 2014
  #2
The signal is correlated but the noise is not correlated, which will give you 3dB better S/N per capsule. Someone can probably explain it better than me.
Old 22nd December 2014
  #3
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Quote:
Originally Posted by Aural Endeavors View Post
Someone can probably explain it better than me.
I hope so! Thanks though. Mainly interested in how the capsules are positioned and how the signals are summed.
Old 22nd December 2014
  #4
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Don't buy that microphone. It is a budget version of the real thing.

DPA only makes two capsules. This is their way of trying to offer an omni microphone with the capsules that they make in house.

The real omni capsules are still made by Bruel & Kjaer and DPA buys these from B&K for their premium omnis like the 4006 and 4007 and the other variants.

If you require top top performance in omni technique, never buy the budget "wanna-be" version that DPA promotes right now.
Old 22nd December 2014
  #5
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Quote:
Originally Posted by Plush View Post
Don't buy that microphone. It is a budget version of the real thing.

DPA only makes two capsules. This is their way of trying to offer an omni microphone with the capsules that they make in house.

The real omni capsules are still made by Bruel & Kjaer and DPA buys these from B&K for their premium omnis like the 4006 and 4007 and the other variants.

If you require top top performance in omni technique, never buy the budget "wanna-be" version that DPA promotes right now.
Thanks for your input. Yeah I was aware of this. However from the samples I think the 2006 sounds like a very good omni; I'm not sure it's value is precisely correlated to its price, compared to the 400x series. The impetus of this post was pretty much that I found it disappointingly lame that the mic is not the 1/2" mic it appears to be.

Still the technology they're using here is just a point of interest - a unique design. A better comparison would probably be the Earthworks M30, at around the same price but higher noise.
Old 22nd December 2014
  #6
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Quote:
Originally Posted by szegedin View Post
Still the technology they're using here is just a point of interest - a unique design.
Line Audio has used this technique for years to create an LDC out of SDC's: Line Audio Design - discontinued products
Old 22nd December 2014
  #7
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Quote:
Originally Posted by Earcatcher View Post
Line Audio has used this technique for years to create an LDC out of SDC's: Line Audio Design - discontinued products
Cool that looks good -- 6 diaphragms, far out! How do they sound?
Old 22nd December 2014
  #8
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Quote:
Originally Posted by szegedin View Post
Cool that looks good -- 6 diaphragms, far out! How do they sound?
The examples I heard sounded pretty good, particularly for the moderate price they used to command. Unfortunately they are only available used (when they are), as the maker has no time to make them anymore. I had a surround version (QM12 Quad) on my buying list. Too bad.
Old 22nd December 2014
  #9
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Quote:
Originally Posted by Earcatcher View Post
QM12 Quad
Is that an ambisonic mic? I've seen those 4 cap ambisonic mics, but of course those have separate preamps.
Old 23rd December 2014
  #10
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Quote:
Originally Posted by Plush View Post
DPA only makes two capsules. This is their way of trying to offer an omni microphone with the capsules that they make in house.
You saying they're using back-to-back cardioids, to make an OMNI?? That sounds like a terrible idea. Boy, would THAT be 'the worst of both worlds'!
Old 23rd December 2014
  #11
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Quote:
Originally Posted by Joe Polizzi View Post
You saying they're using back-to-back cardioids, to make an OMNI?? That sounds like a terrible idea. Boy, would THAT be 'the worst of both worlds'!
That would be the worst of both worlds. But no, it's two omni caps. I really don't know if they are back to back or side by side or what.
Old 23rd December 2014
  #12
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Back to back is the only thing that makes sense if you want to shrink the size. Side by side would produce the equivalent front face (actually bigger) as a single larger membrane.

The quoted text in this thread also says "opposite facing".
Old 23rd December 2014
  #13
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Quote:
Originally Posted by Joe Polizzi View Post
You saying they're using back-to-back cardioids, to make an OMNI??
I understood that the capsule of the 2006 is composed of two omni capsules from the 4060 / 4090.
Old 23rd December 2014
  #14
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They are omni capsules, not back to back cardioid capsules.

I would say that the essence of my post is that the 2006 is a bright sounding microphone and not in the family of sound of a 4006. It is not as precision a build when it uses the in-house made DPA miniature capsules as the Bruel & Kjaer capsules in the 4006.

Buyers will not obtain the 4006 sound when purchasing the 2006.

You get exactly what you pay for in European made products.
Old 23rd December 2014
  #15
Quote:
Originally Posted by szegedin View Post
Say what? I'm not sure I get this. The two capsules are facing opposite (front/back or side/side?) one on top or next to the other, or just back to back? And this is true of both the omni and cardioid versions, the latter of which uses an interference tube to make it cardioid.
Hi Szegedin,

Almost all multipattern mics use this same technique, they just aren't explicit about it. u87s, 4050s, 414s, 800s, and all your favorite old tube mics with power supplies and pattern selectors -- they all have two back-to-back diaphragms/capsules.

As a case study, take a look at the Sennheiser TWIN. It is the same as the MKH 800, but instead of the capsules being combined in the mic, you have separate outputs for the front and back capsule. By changing the level and phase, you can get omni, cardioid, figure-8, and anything in between.

This is why some people talk about "pressure condensers" or "true omnis" when talking about using omnis. They want to distinguish between "real" omnis and dual-diaphragm omnis. This doesn't mean that other omnis don't sound good - it's just different.
Old 23rd December 2014
  #16
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Quote:
Originally Posted by Audiop View Post

The quoted text in this thread also says "opposite facing".
Doh, yeah You're right. But still we don't have any definitive information as to whether they are back to back or opposite facing and stacked. The mic appears to be 1/2" diameter (correct me if I'm wrong) not 1/4". And they could just as well be facing side to side, but that seems unlikely.

Quote:
Originally Posted by NorseHorse View Post
Hi Szegedin,

Almost all multipattern mics use this same technique, they just aren't explicit about it. u87s, 4050s, 414s, 800s, and all your favorite old tube mics with power supplies and pattern selectors -- they all have two back-to-back diaphragms/capsules.

As a case study, take a look at the Sennheiser TWIN. It is the same as the MKH 800, but instead of the capsules being combined in the mic, you have separate outputs for the front and back capsule. By changing the level and phase, you can get omni, cardioid, figure-8, and anything in between.

This is why some people talk about "pressure condensers" or "true omnis" when talking about using omnis. They want to distinguish between "real" omnis and dual-diaphragm omnis. This doesn't mean that other omnis don't sound good - it's just different.
Thanks for that - yes I was aware of this 'fake' omni phenomenon and to my ears there is a difference. The cheap CAD m179 must use the same techneique as that Sennheiser twin you're talking about.

I'd just never seen this summed dual omni design before. Since posting this thread I have read that some DIYers have emulated this with cheap omni caps to favorable (for the price) results. Wiring in parallel.

Plush thanks for your first-hand info on the 2006. I'm not considering buying it, just interested in the design going on there. I agree that the price is not right relative to the 4006, which I consider a 'bargain' since there are more expensive mics out there, but to my ears none better. With the 2006 they are just flogging the DPA reputation, but one has to admit the noise spec is better than the 4060. It's not a 4060.

As for "you get what you pay for" -- IMHO this is the most over-repeated, demonstrably false piece of echolalia on this forum, but that is the topic for another thread.
Old 24th December 2014
  #17
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The 4060 is the most omnidirectional mic I've come across, great for
reverberant spaces with good acoustics, when used with it's grid removed. It's an indication of how the future of omnidirectional mics will develop as manufacturing and electronics become more refined with 1/4 inch capsules. I haven't tried the 2006 but the directionality charts look odd to me.
Old 24th December 2014
  #18
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Quote:
Originally Posted by aracu View Post
I haven't tried the 2006 but the directionality charts look odd to me.
Maybe it's because manufacturers don't usually post polar pattern at such high frequencies?

This is the 2006a



This is the 4006 with "standard" grid thingy.



I think both of these can be more (and less) directional with different grids.
Old 24th December 2014
  #19
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4060 w/ standard grid:
Attached Thumbnails
DPA 2006 twin diaphragm design: not sure I get this-4060.jpeg  
Old 24th December 2014
  #20
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Quote:
Originally Posted by aracu View Post
4060 w/ standard grid:
Yep I saw that, it's interesting. But I would rather have a touch of directionality if I can have that, and still have the key advantages of omnis, which is not the pattern, but the low (and high) end response and ability to close mic without drowning in an avalanche of mud. To me, omnis are about, oh well, okay, that's the pattern I have to work with for that sound.
Old 24th December 2014
  #21
Quote:
Originally Posted by Plush View Post
They are omni capsules, not back to back cardioid capsules.
Hi Szegedin -- Just read the microphone description more closely and realized that the DPA 2006 microphone is not necessarily the same as the other mics are mentioned, which are back-to-back cardioid capsules, and therefore side-address.

The 2006 is end-address, and if Plush is correct, has two omni capsules. Perhaps just to reduce noise, as Aural Endeavors described?
Old 24th December 2014
  #22
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Quote:
Originally Posted by NorseHorse View Post
The 2006 is end-address, and if Plush is correct, has two omni capsules. Perhaps just to reduce noise, as Aural Endeavors described?
Yep, that much I understood from the description off the bat . It is two omnis. Still dead curious as to whether they are stacked side by side, one facing front the other rear -- because the mic seems to be 1/2" diameter. Anyone want to volunteer to rip one apart? The other thing is how they are wired. I read of a DIYer constructing a similar mic, for the purpose of lowering noise. He said it was wired "parallel" but you could see in his pictures it was wired in serial, one capsule to the next, and merrily on its way to the preamp. The DPA may be a tad more sophisticated.

I think it's a neat concept. It's worth noting that the area of two 1/4" capsules combined (28.27mm2 x 2 = 56mm2) is still half the area of one 1/2" capsule (113mm2). I was wrong in stating off the cuff that two quarter inchers gives you the surface area of a half incher, which tells you something about math education in the states
Old 24th December 2014
  #23
Perhaps DPA faced them that way to give less directionality of the higher frequencies (front and back opposed to just the front).

Whenever I have time, I might experiment with my Avenson STO-2s by wiring 3 each per side (I have six of them). Those are very omni as well.
Old 24th December 2014
  #24
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Quote:
Originally Posted by Aural Endeavors View Post
Perhaps DPA faced them that way to give less directionality of the higher frequencies (front and back opposed to just the front).
I would agree with you, but it didn't seem to work. Doesn't the high frequency directionality have to do with the body of the mic 180 degrees off axis?

Quote:
Originally Posted by Aural Endeavors View Post
Whenever I have time, I might experiment with my Avenson STO-2s by wiring 3 each per side (I have six of them). Those are very omni as well.
Big thumbs I applaud and support your experiment, thou bold tinkerer! Never heard those Avensons, but I bet you'll like what you hear, having higher sensitivity and much needed lower noise. Do let us know on this thread if you do.
Old 24th December 2014
  #25
Quote:
Originally Posted by szegedin View Post
I would agree with you, but it didn't seem to work. Doesn't the high frequency directionality have to do with the body of the mic 180 degrees off axis?
Yes, and most likely explains the slight comb filtering effect on some of the polar patterns due to the interaction of both capsules/body positions/proximity. If only one capsule was used, my guess is the pattern would be smoother. Always a compromise. The other explanation could be that facing them the same direction gave worse results because of more housing behind both capsules, and facing them toward each other smoothed the pattern a little. Just a guess; I actually haven't seen or used the mics; I'm totally unfamiliar with them, but know and own the 4006As.

Quote:
Originally Posted by szegedin View Post
Big thumbs I applaud and support your experiment, thou bold tinkerer! Never heard those Avensons, but I bet you'll like what you hear, having higher sensitivity and much needed lower noise. Do let us know on this thread if you do.
They're very neutral as-is and seem to pick up more room than the 4006As. They don't seem as fast, though, but that may be due to their high self noise. I may have a different opinion after the experiment. One advantage they have regarding their "omniness" is their very small diameter bodies, which eventually meet the larger diameter portion. Configuring them 3 per side will end up with the capsules being about 2 or more cm from each other I think, which may require atypical placement. Not sure how this distance will effect S/N, but am guessing not much.

Last edited by Aural Endeavors; 24th December 2014 at 09:20 PM.. Reason: Spelling
Old 24th December 2014
  #26
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Quote:
Originally Posted by Aural Endeavors View Post
They don't seem as fast
Smaller capsule = faster transient response IIRC Edit: Oh you meant the DPA is faster. In that case, maybe it's the nickel diaphragm?

Quote:
Originally Posted by Aural Endeavors View Post
Configuring them 3 per side will end up with the capsules being about 2 or more cm from each other I think, which may require atypical placement. Not sure how this distance will effect S/N, but am guessing not much.
I think to do it right you would have to get the caps out of your valuable mics and get them right next to each other -- this is where the bravery comes in -- because if they are 2cm apart they will be out of phase at high frequencies. A 20khz wave is about a half inch long.

Wavelength
Old 24th December 2014
  #27
Yeah, I'll have to listen to make a judgment; my ears will tell me. I may pull them further apart on a bar as well. I won't pull out the capsules, however.
Old 24th December 2014
  #28
There's also the option of angling them to get them very close, which I forgot to mention.
Old 24th December 2014
  #29
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Quote:
Originally Posted by Aural Endeavors View Post
There's also the option of angling them to get them very close, which I forgot to mention.
Hmm well if you're not willing to get the caps out and put them together, you're talking about a mic array of sorts, really. Summing the signals post mic preamplifier, I assume. I'm not sure whether this will result in an apparent decrease in noise, since the s/n ratio is 'done'. Maybe someone can chime in. This will get you an apparent increase in sensitivity to the extent that the signal is in phase. Shrug. If the caps are spaced out to any degree, it results in a mishmash of comb filtering that can be calculated in advance. Not to say it would be a bad sound, but it's not a mic. For one thing, you're dealing with three or four cables, taking up three or four preamp channels. Additionally, jamming the capsules together in any arrangement would result in more mic body behind each capsule, and a weird polar pattern. Again, not that weird is bad.

This is getting pretty far from what the DPA 2006 is doing, which is to achieve a phase coherent summing of the two caps in one clean, quiet, fast line; something better than one 1/4" cap. And maybe better than some 1/2" caps, although not better than DPA's own.
Old 25th December 2014
  #30
Quote:
Originally Posted by szegedin View Post
Hmm well if you're not willing to get the caps out and put them together, you're talking about a mic array of sorts, really. Summing the signals post mic preamplifier, I assume. I'm not sure whether this will result in an apparent decrease in noise, since the s/n ratio is 'done'. Maybe someone can chime in. This will get you an apparent increase in sensitivity to the extent that the signal is in phase. Shrug. If the caps are spaced out to any degree, it results in a mishmash of comb filtering that can be calculated in advance. Not to say it would be a bad sound, but it's not a mic. For one thing, you're dealing with three or four cables, taking up three or four preamp channels. Additionally, jamming the capsules together in any arrangement would result in more mic body behind each capsule, and a weird polar pattern. Again, not that weird is bad.

This is getting pretty far from what the DPA 2006 is doing, which is to achieve a phase coherent summing of the two caps in one clean, quiet, fast line; something better than one 1/4" cap. And maybe better than some 1/2" caps, although not better than DPA's own.
I'm not trying to design a new mic; I'm just experimenting with the tools I have to get more out of them. I've been doing this kind of thing for over 30 years, and have come up with a few unique things along the way.

This whole concept is nothing new, by the way; others have been doing it for years, so it's not anything innovative or novel DPA is doing here, and I'd argue it's a stretch to say that it's the future of mic design. It's obvious that compromises have been made, looking at the polar patterns. You can't get something for nothing. Furthermore, DPA isn't going to sell a far less expensive piece that will give their flagship model a run for its money. Also, I personally believe you DO get what you pay for as far as the 4006A is concerned.

Even though theory states that the smaller capsules are faster than the relatively larger ones, that's not what my ears tell me when it comes to the 4006A; it's the fastest I've personally come across when using and listening to it in practice. Perhaps the nickel has something to do with it.

As far as the Avenson mic array goes, it has its own advantages due to their very thin mic bodies, which will allow more placement options and possibly less phase issues when carefully placed. I'll also listen at right angles, and facing each other as well, varying the distance while listening. I can do this easily because I always utilize my custom IEMs when placing mics.

As far as the S/N goes, AFAIK, the noise is still non-correlated even when using multiple mic preamps when the capsules are placed close enough to each other. The noise should still add up as the root of the sum of the squares. However, I haven't measured it myself, but will if I ever get around to doing this experiment.

Merry Christmas!
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