Mid-Side Question

[NoddyFingers]

Hi Folks,

When setting up for Mid-Side recording/processing why MUST the Side-Mic be Fig-8?
Why is it not possible to use a Cardioid or Omni pointed at right-angles to the Mid-mic, then copying the side mic track and inverting the phase just as you would normally do with the Fig-8 Side-mic.

If it is not possible, can anyone explain why?

Many Thanks

[sdelsolray]

Originally Posted by NoddyFingers

Hi Folks,

When setting up for Mid-Side recording/processing why MUST the Side-Mic be Fig-8?
Why is it not possible to use a Cardioid or Omni pointed at right-angles to the Mid-mic, then copying the side mic track and inverting the phase just as you would normally do with the Fig-8 Side-mic.

If it is not possible, can anyone explain why?

Many Thanks

You can use two cardioids, with appropriate mic positioning and post recording track processing, to replace the figure 8 mic, as that would approximate what the figure 8 mic hears. Two omnis? Not as close.

[Fran Guidry]

Originally Posted by NoddyFingers

Hi Folks,

When setting up for Mid-Side recording/processing why MUST the Side-Mic be Fig-8?
Why is it not possible to use a Cardioid or Omni pointed at right-angles to the Mid-mic, then copying the side mic track and inverting the phase just as you would normally do with the Fig-8 Side-mic.

If it is not possible, can anyone explain why?

Many Thanks

Stereo works because the two mics are arranged to capture different information.

Your idea of using a single cardioid or omni for a side mic then inverting that signal for the opposite side would result in the two side mic signals cancelling completely since they are the same signal, and the final result would be mono, the signal from the mid mic by itself.

These two articles explain stereo mic techniques:
http://www.soundonsound.com/sos/1997...reomiking.html
http://www.soundonsound.com/sos/1997...mictechs2.html

This document gives a detailed explanation of mid-side: http://www.midside.com/pdf/nyu/masters_thesis.pdf

Fran

[RRuskin]

Originally Posted by sdelsolray

You can use two cardioids, with appropriate mic positioning and post recording track processing, to replace the figure 8 mic, as that would approximate what the figure 8 mic hears. Two omnis? Not as close.

You would be hard pressed to get a true/complete null with 2 cardiods positioned back-to-back.

[sdelsolray]

Originally Posted by RRuskin

You would be hard pressed to get a true/complete null with 2 cardiods positioned back-to-back.

Mid sid with two cardioids can be (approximately obtained if the two cardioids (pointed 180 degrees from each other to act as the figure 8 side mic):

(i) were summed to one track (T1),

(ii) that summed track was duplicated (T2),

(iii) T1 was panned 100% left in a stereo mix,

(iv) T2 was panned 100% right in a stereo mix,

(v) the polarity of either T1 or T2 were reversed and

(vi) the mid mic track (T3) was panned dead center in the stereo mix.

T1 and T2 should completely null if collapsed to mono.

[RRuskin]

Originally Posted by sdelsolray

Mid sid with two cardioids can be (approximately obtained if the two cardioids (pointed 180 degrees from each other to act as the figure 8 side mic):

(i) were summed to one track (T1),

(ii) that summed track was duplicated (T2),

(iii) T1 was panned 100% left in a stereo mix,

(iv) T2 was panned 100% right in a stereo mix,

(v) the polarity of either T1 or T2 were reversed and

(vi) the mid mic track (T3) was panned dead center in the stereo mix.

T1 and T2 should completely null if collapsed to mono.

Theoretically possible. In practice, not so much.

[sdelsolray]

Originally Posted by RRuskin

Theoretically possible. In practice, not so much.

When I tried it worked well, although it is a bit more mechanical to get to the end result.

[Doug Young]

I've always suspected the "magic" of MS comes from the way it gets as close as possible to true coincidence and phase coherence, by truly having each side of the stereo image coming from the same mic capsule, closer to theoretically perfect than you can get with 2 mics in X/Y, for example. MS usually seems to have a remarkable stereo image. I'd guess that you might not be able to get that same benefit from 2 cardiods. Of course, you might get some other sound you like.

[NoddyFingers]

Thanks everyone for your time and very informative replies.