M/S mic'ing: substitution of bi-directional mic?

Posted: Sat May 24, 2008 7:39 pm

I've been wanting to experiment more with the Mid-Side technique, but I don't own a bi-directional / figure-8 microphone. Would I get comparable results standing in two identical cardioid LDCs for the side mic? Some provocations:

1.) The two LDCs I have in mind have good off-axis rejection. It wouldn't create a null spot as a figure-8 mic would, but I don't know how paramount this is to the effect.

2.) The above isolated, it seems to me that the extra few inches' difference between the diaphragms of the cardioid side mics ( versus no difference in a figure-8 ) should be negligible, provided each cardioid is equidistant to the mid mic.

I haven't read about anybody doing this, so I have to consider there's a reason for that. But I wanted to get opinions to be sure.

Posted: Sat May 24, 2008 11:47 pm

or
two R-shack PZMs back to back

Guerrilla Audio
got to make do with what you have ... or can borrow ... or make (DIY) ... or ...

Posted: Mon May 26, 2008 1:42 pm

It is possible and the results are usable but the question is - why do it? M/S can be a great tool, but it's not an ideal tool save maybe a few unusual situations.

That being said - it is paramount that you wire the right cardioid mic out of phase (reverse) from the left.

You should have a decent null when doing this as the overlapping patters should cancel (or darn near it).

To avoid the issue of capsule distance (which will actually make a pretty big difference), try mounting the 3 mics one above eachother such as:

<--
o
-->

The arrows being the side-facing mics and the o being the front facing.

Posted: Tue May 27, 2008 6:19 am

I agree with Jeremy, but...

For my money it's much easier to rewire a cable than a mic. I would rewire the cable out of phase and just mark it accordingly. I do this for a HHb Cd recorder I have. Then the mic can still be used as intended.

Much, much easier.

Phil

Posted: Tue May 27, 2008 6:52 am

Oh, I agree. I'm making the assumption however, that the mic or the preamp or the software has a polarity reverse switch...

Posted: Tue May 27, 2008 8:06 am

I bought a pair of the Cascade Fathead mics they have on sale from time to time, partly with the idea of using them in M/S mode. With the kit, you get a nice case, blumlein stereo bar, clips, etc.; everything you need for an M/S configuration. (Except the out of phase cable, which I just create virtually in my Sequoia/Samplitude software anyway when I mix in post...)

I've used them in a couple of situations now, and they work quite nicely, esp with that warmer, more rounded ribbon sound. For a shallow but wide brass ensemble, they gave me as much width as I needed, dialing in the stereo image to taste. Just a few weeks ago, I recorded an electronic/simulated pipe organ (as part of a larger ensemble, functioning mostly as a continuo) and was faced with a Loft area dedicated to the organ about 60-70 feet wide, and about 15 feet deep. Due to a center stairwell and placement of the rest of the ensemble even further out from the organ area, I couldn't get very far back away from the organ to get the whole image as I'd like. The M/S pair did the trick nicely; I could make it as wide or as narrow as I needed to fit it properly in the mix.

I've done M/S with a lot of different mics over the years, but the biggest factor, IMHO, is to keep all the parts involved as evenly matched and accurate as possible. I've heard the image "Swimming" from a variety of variables, and again, the more uniform you can make all the components, the more solid the image, stereo spread, etc.

Posted: Wed May 28, 2008 4:54 am

Rather than futz with wiring, I'd try it by recording 3 tracks - Mid, Left and Right. When done recording, carefully match the levels on the right and left sides. Invert the right track & sum the left and right together. That's your SIDE track.

In both of the programs I use for this kind of work, I can flip phase on just the right channel when mixing MS - in Samplitude it's in the PAN control, and Audition has a "Channel Mixer" effect which works well. That keeps the MS on two tracks. Just mix the mid and side (right channel flipped) to taste. If you can't get it done in two tracks, copy the SIDE track to a third track - flip phase on that one and pan it hard right. Pan the first SIDE track hard left.

Either way it should give you a reasonable facsimile of MS.

Posted: Sun Jun 01, 2008 3:16 pm

Thanks, guys.

Posted: Mon Jul 28, 2008 2:54 pm

Don't wire a condenser or ribbon mic out of polarity!!! Safer to do it in the software.

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