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Author Topic: Building your own binaural mics ~ $20  (Read 27957 times)

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Offline Scooter

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Re: Building your own binaural mics ~ $20
« Reply #30 on: August 08, 2008, 03:51:42 PM »
scrounged up this Primo link from text above.  kinda interesting.  20Hz-10k response though....  might be fun to play with, and kinda stealthy.

http://cgi.ebay.com/NEW-Primo-CM4052PMI4-Precision-Condenser-Microphone_W0QQitemZ230243213961QQihZ013QQcategoryZ50590QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
MBHO 603a(ka200n/ka500hn) >
R-44, or H120

LMA Recordings

Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #31 on: August 08, 2008, 04:22:53 PM »
scrounged up this Primo link from text above.  kinda interesting.  20Hz-10k response though....  might be fun to play with, and kinda stealthy.

http://cgi.ebay.com/NEW-Primo-CM4052PMI4-Precision-Condenser-Microphone_W0QQitemZ230243213961QQihZ013QQcategoryZ50590QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
I have had quite a few pairs of these. They actually sound very good very warm sounding although they are huge! they can be modified to run 2 wire or three wire. And the short cables are easily replaced. They only take a max of 12 volts.

Chris
for warranty returns email me at
EMAIL Sales@church-audio.com

Offline Scooter

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Re: Building your own binaural mics ~ $20
« Reply #32 on: August 08, 2008, 05:00:24 PM »
good to know ;)
MBHO 603a(ka200n/ka500hn) >
R-44, or H120

LMA Recordings

Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #33 on: August 08, 2008, 05:36:23 PM »
@Chris
which Primo caps do you stock?


Em123, 125, em135 and (EM63. but I only have two of these) The others I have quite a few of.




Chris
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Offline anechoic

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Re: Building your own binaural mics ~ $20
« Reply #34 on: August 08, 2008, 06:37:26 PM »
I sent you a pm about the EM-125
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small, highly mobile, independent and intelligent.'
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Offline marksk

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Re: Building your own binaural mics ~ $20
« Reply #35 on: August 09, 2008, 06:09:46 PM »
i don't see the em-63 on their site, is it similar to the em-68?

the 68 says it can be configured as a 2-wire or 3-wire mic. is this done by wiring two of the terminals to ground?

Offline illconditioned

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Re: Building your own binaural mics ~ $20
« Reply #36 on: August 09, 2008, 07:43:23 PM »
i don't see the em-63 on their site, is it similar to the em-68?

the 68 says it can be configured as a 2-wire or 3-wire mic. is this done by wiring two of the terminals to ground?

Em68 has three wires (two on the PC board, one to the case).  You can run either two wire or three.
I don't know the color of the wires though.

If it is like AT853, then there are three: shield, yellow and red.
There are three possibilities:
- short yellow to shield, red to miniplug: this is two wire
- put a 4.7k resistor between yellow and shiedl, red to miniplug: this is two wire "4.7k mod"
- keep three wires, red, yellow, shield > 3 wire battery box

Internally all AT853 mics use the third option, with a 5.1k resistor inside for a load.  So, the 4.7k mod is OK.  Disadvantage is it loses pprox 6-12dB gain, but to avoid distortion it is well worth it IMO.

  Richard
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline anechoic

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Re: Building your own binaural mics ~ $20
« Reply #37 on: August 09, 2008, 07:58:11 PM »
mod'ing Behringer ECM8000 mics:
http://www.directap.com/Microphones.htm
you can pick these up for around $50 USD new
I'm sure you can find them around used as well
'In the new world the characteristic unit will be
small, highly mobile, independent and intelligent.'
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Offline anechoic

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Re: Building your own binaural mics ~ $20
« Reply #38 on: August 09, 2008, 08:17:54 PM »
scrounged up this Primo link from text above.  kinda interesting.  20Hz-10k response though....  might be fun to play with, and kinda stealthy.

http://cgi.ebay.com/NEW-Primo-CM4052PMI4-Precision-Condenser-Microphone_W0QQitemZ230243213961QQihZ013QQcategoryZ50590QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
I have had quite a few pairs of these. They actually sound very good very warm sounding although they are huge! they can be modified to run 2 wire or three wire. And the short cables are easily replaced. They only take a max of 12 volts.

Chris


@Chris
it's hard to tell from the photo on eBay but these Primo mic bodies won't take the EM-23 caps...will they?

edit: the eBay spec says the Ø is 14 mm
the EM-23 spec states the cap Ø is 21 mm
so I guess they won't
what would be a good replacement cap that has a better self-noise and top end?
:)
« Last Edit: August 09, 2008, 08:27:58 PM by anechoic »
'In the new world the characteristic unit will be
small, highly mobile, independent and intelligent.'
                                - Robert Fripp

Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #39 on: August 09, 2008, 08:21:17 PM »
scrounged up this Primo link from text above.  kinda interesting.  20Hz-10k response though....  might be fun to play with, and kinda stealthy.

http://cgi.ebay.com/NEW-Primo-CM4052PMI4-Precision-Condenser-Microphone_W0QQitemZ230243213961QQihZ013QQcategoryZ50590QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
I have had quite a few pairs of these. They actually sound very good very warm sounding although they are huge! they can be modified to run 2 wire or three wire. And the short cables are easily replaced. They only take a max of 12 volts.

Chris


@Chris
it's hard to tell from the photo on eBay but these Primo mic bodies won't take the EM-23 caps...will they?
:)

No these are smaller capsules they were used on a pair of nak capsules I forget the model number but they are identical. These were analyser capsules they all come with a calibration chart! Its a pretty good deal but again not much action about 14k

Chris
for warranty returns email me at
EMAIL Sales@church-audio.com

Offline digifish_music

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Re: Building your own binaural mics ~ $20
« Reply #40 on: August 09, 2008, 11:40:59 PM »
mod'ing Behringer ECM8000 mics:
http://www.directap.com/Microphones.htm
you can pick these up for around $50 USD new
I'm sure you can find them around used as well


Thanks for the (great) link.

About the (miss attributed) "Linkwitz Mod" is actually the "Lyman Miller" mod.

While this may improve the mics high SPL performance, but does so at the expense of S/N for quiet recordings. I am disappointed how quickly people rush to this mod without thinking of the intended application for the mic.

digifish
- What's this knob do?

Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #41 on: August 09, 2008, 11:51:52 PM »
mod'ing Behringer ECM8000 mics:
http://www.directap.com/Microphones.htm
you can pick these up for around $50 USD new
I'm sure you can find them around used as well


Thanks for the (great) link.

About the (miss attributed) "Linkwitz Mod" is actually the "Lyman Miller" mod.

While this may improve the mics high SPL performance, but does so at the expense of S/N for quiet recordings. I am disappointed how quickly people rush to this mod without thinking of the intended application for the mic.

digifish

Yes that is true about the mod.. The site is kinda scary though this picture scared the crap out of me...
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Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #42 on: August 10, 2008, 12:55:54 AM »
While this may improve the mics high SPL performance, but does so at the expense of S/N for quiet recordings. I am disappointed how quickly people rush to this mod without thinking of the intended application for the mic.

That's really not true per se.  It very much depends on the following circuit.  The inclusion of a source resistor greatly reduces distortion at all levels, not just the very high SPLs where you might hear clipping.  But besides, it doesn't necessarily increase self-noise.

The schemos on that site are all source follower configuration, where the gain of the FET is essentially unity.  If the following stage is nearly as noisy as the capsule noise, then yes, you will degrade self-noise.  But the noise limitation of these capsules isn't the FET, it's the capsule itself.

Where you might run into trouble is with a "two-wire" configuration, where you are operating the capsule FET in common source configuration.  If you increase the value of the source resistor above your bias supply resistor, you will attenuate the capsule signal, and the self-noise of the following amplifier stage could become a factor.  This can be avoided by selecting suitable values for the two resistors, and also a suitable supply voltage.

Or you may simply be feeding a noisy preamp, such that even unity gain results in a noise level below the equivalent input noise of the preamp.  But that's not a mic noise problem, it's a noisy preamp problem.

Incidentally, many of the conclusions about the circuits on that website are basically wrong or misguided.  For example, if you want to simplify the circuit, why keep both PNP transistors with one ground-referenced?  When with the same number of components, you could pull a balanced signal off the capsule FET as a phase splitter (as in the Schoeps circuit)?  The advantage of Schoeps is an extra 6dB of sensitivity, which is gonna help that preamp noise problem, to be sure.

I also love his last circuit--NOT!  Seriously, he's afraid of zener diodes?  That's because he hasn't filtered them properly!  Again, study the Schoeps circuit and see how it is done--the zener regulation of the capsule has some series resistance to improve the function of the filter capacitor.  He hasn't done that, that's why he goes zener-less.

But that comes at a cost--he has to select the value of R7 to work within a relatively narrow range of phantom supplies.  There's really no reason for that; any electret mic should be designed to work from 12V to 48V with no fuss.  So I think Behringer has built a better circuit than he has, although I agree there are redundancies in Behri's circuit and probably components that could be improved in quality.  Still, Behri has made some better decisions--6V for the zener is plenty to keep the capsule happy, and it is less noisy than a 12V zener.  Therefore, Behri's noise filtration works better, even though I don't think either is adequate.  Of course, Behri didn't use the source resistor, so their SPL handling will be limited.

I love his statement that he hasn't tested his last circuit.  How does he know it is quieter?  It might be, it might not.  12V zeners are noisy beasts, and very inconsistently so.  He could select a particularly bad zener and think he was a genius for omitting it, but that is still no substitute for a better circuit design.

I suspect most of his circuit improvement comes from the higher quality of WM61A over the Behri capsule (NOT a Panasonic capsule, despite what you might hear on the interwebs), and of course the addition of the source resistor.  The rest of his circuits are rubbish compared with the well-known Schoeps.

Rubbish wow... Wonder what you think of my circuits... BTW did you get my pm?  ;)

Chris
for warranty returns email me at
EMAIL Sales@church-audio.com

Offline Kindguy

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Re: Building your own binaural mics ~ $20
« Reply #43 on: August 10, 2008, 03:14:22 AM »
Love the DIY great job Tzzzz around.
TDS!

DPA 4023> aeta PSP-2> Apogee Mini Me > R-44

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Offline Church-Audio

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Re: Building your own binaural mics ~ $20
« Reply #44 on: August 10, 2008, 10:30:33 AM »
scrounged up this Primo link from text above.  kinda interesting.  20Hz-10k response though....  might be fun to play with, and kinda stealthy.

http://cgi.ebay.com/NEW-Primo-CM4052PMI4-Precision-Condenser-Microphone_W0QQitemZ230243213961QQihZ013QQcategoryZ50590QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
I have had quite a few pairs of these. They actually sound very good very warm sounding although they are huge! they can be modified to run 2 wire or three wire. And the short cables are easily replaced. They only take a max of 12 volts.

Chris


@Chris
it's hard to tell from the photo on eBay but these Primo mic bodies won't take the EM-23 caps...will they?

edit: the eBay spec says the Ø is 14 mm
the EM-23 spec states the cap Ø is 21 mm
so I guess they won't
what would be a good replacement cap that has a better self-noise and top end?
:)

There is no cap I know of that will fit on this mic. But improvements might be able to be made to the existing capsule to improve the top end
Think about the mic capsule housing it self. Part of the problem with this mic is the silly little phase plug they put in front of the capsule.

Chris
for warranty returns email me at
EMAIL Sales@church-audio.com

 

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