Why a dual diaphram mic cannot be a stereo mic ?

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Why not, but it would make a really weird stereo image, two cardioid patterns in 180' angle. Phase coherence would be great though.
 
I have a Josephson C720, which operates exactly as you suggest.

I use it a lot - drum room stereo mic etc.  Once you get used to what it is doing, it is not at all weird. And it sums back to omni in mono, of course!

And you can do all sorts of other things too, like dial in proximity effect after tracking....

http://xaudiaelektrik.blogspot.com/2010/02/recording-with-josephson-c720.html
 
I didn't know that i want one
don't see it on the josephson site ?
.............ah apparently only 20 made

thanks for the info , you'd think
they would have to be well matched ?
 
okgb said:
thanks for the info , you'd think they would have to be well matched ?

It would certainly help. This one seems very well matched. Josephson make their own capsules so I guess they can cherry-pick & tweak for the application.

For a DIY mic I guess it wouldn't matter so much. Most rooms aren't symmetrical anyway!
 
Actually surpising we don't see this more often. Maybe it's because it's non-standard ? Or not wanting too leave too many options open for the mix (could be a justification for not having it). Or would it become too obvious that many dual-capsules aren't that well matched ? Just all speculating....

Assuming the capsule being the most expensive, just adding a 2nd buffer (for not much more money) & some convenient way to get this signal outside (say XLR-5) would do the trick.

There's for instance an (expensive) Sennheiser that does this:

MKH 800 Twin

http://www.soundonsound.com/news?NewsID=10053

Bye!


 
Sennheiser do it.

http://www.sennheiser.com/sennheiser/home_en.nsf/root/professional_wired-microphones_studio-recording-mics_mkh-800-twin-ni

They do it VERY well.  -They do it with RF biasing (like basically all of their MKH range). They sound fantastic.

The Josephson is a rather different animal in 'S' mode...

A pair of MKH-800-Twins will allow you to matrix a native B-format recording which produces superb results... but at over $10,000 a time it had BETTER be good!

Disclaimer: I am a colossal fan of MKH-800's...
IMG_7332.jpg


 
Sensing both sides of the capsule can be a simple circuit to build.  I just drew up and simmed a simple phantom powered dual follower with two transformer outs and EQ for a K67 like capsule.

Keith do you remember who was posting about building a RF microphone here some years ago?  Building an RF microphone might be something fun and different to do.
 
I just made one , will put it through the paces

Basically I bought an ugly looking  apex 460 tube mice for the supply
and had two of their sd condenser mics that probably due more to the capsules
were inferior to use for serious recording, so

gutted the tube mic , left the capsule , lots of room , used the electronics
from the sd mics and made a breakout box off of the 7 pin cable
discrete dual diaphram stereo mic !
are the capsules and electronics too mismatched ?
I don't know, sounds reasonable , not sure how well matched the capsules are .
 
The tricky part seems to be
what sound is getting to the " on axis "
part of the capsules , depending on if
you're trying to use it as a stereo mic or not
then it may need another mic added with it , but so far i found
the stereo less dramatic than i expected .

Hey Zebra , care to comment on your more successful
applications of it ?
 
Oh, I forgot... Pearl also has done this for several years:

elm-a-l.jpg


http://pearl.se/microphones/elm-a.type

As for building an RF microphone, the advantages are that the impedances are much lower. Difficulties are that they generally use tricky wound components and capsules behave differently. Disadvantages are that they can interact when close to each other, leading to beat/difference frequencies.

I'd be interested if anyone came up with a DIY design though...

Keith
 
okgb said:
Hey Zebra , care to comment on your more successful
applications of it ?

Hi Greg,

With the Josephson, for 'stereo' use I have just been banging it up in the live room, usually on drums perpendicular to the source, and then moving it around until I get something I like. Then blend it in with the the rest of the kit.

On vocals I've been pointing the front at the singer in the usual style, but tracking both capsules. Then you can mix in the back capsule either in phase to be a bit more omni, but usually I blend it in anti-phase, to be a bit closer to figure 8 and to add more proximity effect.

Also it's fun if you compress them differently, or reverb the back, or autotune the back... (no, don't do that!).


Hey Keith, that's a nice bunch of Sennheisers you have there. I'll trade you for a photo of Amy Pond...  ;)
 
Come to think of it a bit more, I recall a Philips-mic from not too long ago uses some capsule-trickery as well. This is all budget-type stuff, using electrets & 3.5mm unbalanced connectors, but the idea is there.
The electrets each seemed to be of a different flavour and were positioned 90 degrees w.r.t. each other.

I thought I traced the circuit then, need to have a look.  Obviously there are many other electret stereo 3.5mm mics out there with a switch for variable stereo-width, but I hadn't seen one that does it in M/S style capsule-wise.

The funny but unintended consequence of this internal construction is that most users seem to aim the mic incorrectly & then discard it as giving weird sound. Some indication would have been nice indeed.
 
> Why a dual diaphram mic cannot be a stereo mic?

It can be. But the only "stereo pattern" is cardioids at 180 degree angle. This may be useful if the source is all-around the mike. Or if you want heavy room sound and are able to move the mike front-back to find the balance. It is generally not suitable for "10th row concert hall" situation: there's no direct sound on-axis to either diaphragm, and capsules of useful size have serious off-axis losses.

A variant puts the diaphragms, not close-parallel but at 90 degrees with a common back-chamber. A further variant has four diaphragms on a common chamber (and large patent fees) which can be decoded to any of the close-pair configurations and many more including up/down separation.
 
PRR said:
> Why a dual diaphram mic cannot be a stereo mic?

It can be. But the only "stereo pattern" is cardioids at 180 degree angle. This may be useful if the source is all-around the mike. Or if you want heavy room sound and are able to move the mike front-back to find the balance. It is generally not suitable for "10th row concert hall" situation: there's no direct sound on-axis to either diaphragm, and capsules of useful size have serious off-axis losses.
Yes to all that.  Back to back coincident cardioids have nothing outside the speaker positions so the speakers draw attention to themselves.  Also very "monoish".

What you can do is convert to M/S, increase the difference S, apply HF boost to the sum M, and convert back to L/R.  I've done this with stick cardioids with good results but not with a dual diaphragm.
 
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