M/S Matrixing and Input linking???

[Gary Nattrass]

I agree with Richard and a shotgun is probably the worst type of mic to use for M/S but there again I did an ITV stereo sound course and they said a lav could be used as the M signal and a boom mic as the S content!

Whatever works in the real world but you must make sure your mono signal is OK but as the M content should always be the key sound source it should be OK.

There were all sorts of phase enhancement processes brought out over the years including Q sound and one from Roland, you also find that some synth stereo keyboard patches are heavily M/S processed to create large width but if you mono them they nigh on fully cancel out !

The best M/S combination tends to be a forward facing cardioid and a figure of eight mic for the S content. I used to have a nice little combo from beyer of a M201 and a M130 as it didn't need phantom power and was good for generic sound effects recording but I then switched to the self contained sony M/S mics like the ECM MS-957 etc as they output A/B which is more convenient to record but you still have a width control that is more fixed and stable.

Where I work now we have the digital soundfield microphones (ex Calrec) but they are very very expensive.

As a kid in the 70's I used to play around with surround before I even knew what it was by hooking up two sets of stereo speakers to my hifi and putting the ones behind me out of phase to give a pseudo surround set-up.

[Jonathan Levin]

Thanks Richard and Gary.

As I continue to look into this, I found that maybe my shotgun (Rode NTG3) may not be the worst choice. This from B&H website:

"As far as capturing your MS recording, you only need two mics and two tracks to record. One mic must be bi-directional (figure 8 polar pattern) and the other is most often directional, or cardioid pattern, although Alan Blumlein described using an omnidirectional transducer in his original patent. Omni will give you a wider-sounding recording with more low end. Feel free to experiment with super or hypercardioid, too!"

There seems to be a few flavors of cardioid mics. The NTG3 is "Super Cardioid" but I am looking at the polar response diagram and it seems to fall into what is close to being used for the Mid mic. For that matter my Rode NT 3 may even be a better choice for Mid, since it is just "cardioid".

Your thoughts? As far as the Side mic, unfortunately I have nothing on hand that as a figure eight pattern to test out.

But even with my first rather unscientific experiment, I do like this a lot. Any recommendations on something that is reasonably priced but pretty decent for a side mic?

Happy Thanksgiving.

Jonathan

[Gary Nattrass]

Yes the NTG3 is a hyper cardioid but it also has a phase cancellation tube in front of the capsule and as M/S basically works on phase principles that may cause all sorts of problems.

The S figure of eight will need to be back before the phase cancellation tube and not ideal for a coherant stereo image.

It would be better to have a cardioid or hyper capsule mic without a phase cancellation tube in front of it but also an omni mic could be used in place of the fig of eight one.

I have also got great results with a takstar CM60 and CM61 combination but as said previously it is far easier to just go for the sony M/S mic that outputs A/B for recording.

It may also be worth experimenting with the AT875R as that has a different phase cancellation concept and may not be as bad as a traditional medium or longer shotgun.

[Richard Crowley]

Without something more like a cardioid "M" microphone and a REAL bi-direcitonal (figure-8) "S" microphone, you don't really have what anyone would call "M-S".

But if you have some combination of random directionality and phasing combination that amuses you, nobody can argue with that. However, it is not clear if there is any practical or useful application?

[Greg Miller]

There is serious problems with using a cardioid mic, pointed house left, instead of a proper bi-directional mic, as your "side" channel. I will call this the "FS" or "fake side" mic.

The most obvious problem is that you have no mic pointed toward house right. So the instruments on the [house] right side (typically the lower strings and brass) will not have any mic that picks them up well. They will be 45º off axis of the "M" mic, and 90º off axis for your "FS" mic. So the mix will tend to discriminate against these instruments.

OTOH the instruments on the [house] left side (typically violins, harp, keyboard) are directly on axis of the "FS" mic, so the final mix will tend to favor those instruments.

Also, if you were to look at the polar response patterns of the mics you propose, you would find that things don't "add up" properly. Ideally with correct M and S mics, the sensitivity and response of the mics overlap in such a way that they produce fairly even coverage across the sound field. As the output of the M mic is dropping off (as the angle away from the centerline increases) the output from the S mic is increasing. The sum of the two should be fairly uniform. If you use a hypercardioid for the M mic, it will drop off much faster than a proper cardioid, resulting in very uneven coverage across the soundfield.

A lot of this could be better illustrated if we plotted some overlapping polar patterns, and actually added values from the graphs. Frankly, I am not going to take the time to do that. But if you don't believe all the above, feel free to do so yourself. (This stuff is intuitively obvious to me, but still ... a picture and math are worth a thousand words.)

As Mr. Crowley indicates, if you find the result interesting, that's your choice. It will certainly result in two channels which are different, so in some sense of the word it will be "stereo." But don't think for a minute that it will produce uniform or correct M/S pickup.