Topic: 2 stereo mics > 2 channel recorder?

[George2]

I'll dumb it down for you.
Generally,it's OK to split an output with a 'Y' adapter.
It's NOT ok to use a 'Y' adapter to combine two input sources, MS or whatever.
You need a mixer.

[yug du nord]

DSatz... you flippin' rock!!!  So... I'm assuming then that when I've used these two M/S mics, that I've only picked up the mono (left M capsule) for the left channel, and mono (right M capsule) for the right channel......  sound correct?  And that is the answer that I've been pickin' yer brain for...  hope it didn't hurt!!!    

Now, I'm wondering about the same mic...  but when I've only used one M/S mic instead of two.  Sony states that the ECM-MS907 directivity is:  Unidirectional x 2

So...  should I assume that means that each capsule is a cardioid?  Where the "M" cap points "north", and the "S" cap points "west"? 

The mic has a switch on the body that you can set to either 90degrees or 120degrees.  So...  does that mean when the setting is at 90deg., that the "S" capsule is at a right angle (90deg.) from the "M" capsule?  Directed at 90deg. to the left of the "M" capsule? 

Or is it that the "S" capsule is 45deg. to the left of the "M" capsule...  so when it's "imaged" to the right channel it would create a 90deg. angle...  with the "M" capsule situated in the middle (at 45deg. of a right angle).  Basically, would it create a 90deg. angle...  where the "M" capsule is at 45deg., and the pick-up pattern would cover 45deg. to the left of "M", and 45deg. to the right of "M"?

Same question but substitute 120deg. instead of 90deg.?  Would the "S" capsule be angled 120deg. to the left from the "M" capsule?  Or, would the "M" capsule be sitting at 60deg., with the pick-up pattern covering 60deg. to the left of "M" and 60deg. to the right of "M"?

And if you look at the picture of the mic, the "S" capsule looks to be facing BOTH to the left and to the right of the mic body.  But the capsule is a "unidirectional capsule", not a "bidirectional cap" (figure 8 ).  What do you think about that?  Is it for aesthetic looks, or is the "S" capsule pointing out the right side of the mic body?  From what I've been figuring out...  a M/S mic configuration is the "M" facing "north", and the "S" is facing "west".  Correct?  So, what would the "S-grill" that is facing to the right("east") be?

Or could it be that the "S" capsule is facing both to the left and right?  But that wouldn't make sense in an actual M/S configuration. 

I have a pretty sweet book that is helping me out as well with these questions...  "Recording Music On Location" by Bruce Bartlett and Jenny Bartlett (2007).  Great book for anyone...  for a teaching tool, or a reference guide!!!  Very modern...  every taper should pick it up.  My gal got it for me off of Amazon.com.  Haven't seen anything this comprehensive for what we do...  seems to be a "Bible of location recording"!!!  So between that book, and you...  I've learned a lot over the past few days!!!  Can't express my gratitude enough man!!!  Thanks again......  +T!!!  300tix on half as many posts...  you are a true asset around here man...  a mind with great things pouring out!!!  May a dare say...  a tapers !!!
                   
                                                         >>>cheers<<<

edit:  tapers angel!!!

[DSatz]

uncleyug, not quite. You've been combining the left output of stereo mike number one with the left output of stereo mike number two, and recording that combination as your left channel. You've also been combining the right output of stereo mike number one plus the right output of stereo mike number two, and recording that combination as your right channel.

As I've said now several times, you can forget about M and S--you were never handling those signals; they only existed inside the microphones. By the time the signals escaped and ran through the wires that you had access to, they were no longer M and S, but left and right.

I suck at drafting, but I may have to resort to some kind of drawing to show you what I mean. Please don't make me do that if you can get my meaning from words alone (except it look as if that's not working so well on one or two of these points).

The 90-degree vs. 120-degree switch doesn't alter the geometric relationship of the M and S microphones (their main axes are always always always 90 degrees apart--M faces forward while S faces sideways). Rather, it affects their relative gain (amount of amplification or derision) prior to matrixing their signals. Those equations (L = M + S, R = M - S) are simplified. One of the great things about M/S recording is the ability it gives you to vary the separation between left and right channels during playback until you find exactly the point between mono and extreeeeeeeeeme stereo that sounds right to you. This is done by varying the relative gain of the M and S signals before matrixing. More S = wider; less S = narrower; no S at all = mono. That's like, if you wanted a narrower stereo playback, you could use L = M + 0.8S and R = M - 0.8S, for example.

That capability is a big reason why M/S is often used in film and video sound recording, and why it was taken up so enthusiastically by European broadcasters in the early days of FM stereo, plus M/S inherently makes mono-compatible stereo recordings; all you have to do to get mono is take the signal from the M microphone by itself. In your case, you'd get the mono by adding the L and R signals together (but use a mixer, bro--don't just parallel the output connectors; that's asking for trouble).

--best regards

[twatts (pants are so over-rated...)]

uncleyug, not quite. You've been combining the left output of stereo mike number one with the left output of stereo mike number two, and recording that combination as your left channel. You've also been combining the right output of stereo mike number one plus the right output of stereo mike number two, and recording that combination as your right channel.

As I've said now several times, you can forget about M and S--you were never handling those signals; they only existed inside the microphones. By the time the signals escaped and ran through the wires that you had access to, they were no longer M and S, but left and right.

I suck at drafting, but I may have to resort to some kind of drawing to show you what I mean. Please don't make me do that if you can get my meaning from words alone (except it look as if that's not working so well on one or two of these points).

The 90-degree vs. 120-degree switch doesn't alter the geometric relationship of the M and S microphones (their main axes are always always always 90 degrees apart--M faces forward while S faces sideways). Rather, it affects their relative gain (amount of amplification or derision) prior to matrixing their signals. Those equations (L = M + S, R = M - S) are simplified. One of the great things about M/S recording is the ability it gives you to vary the separation between left and right channels during playback until you find exactly the point between mono and extreeeeeeeeeme stereo that sounds right to you. This is done by varying the relative gain of the M and S signals before matrixing. More S = wider; less S = narrower; no S at all = mono. That's like, if you wanted a narrower stereo playback, you could use L = M + 0.8S and R = M - 0.8S, for example.

That capability is a big reason why M/S is often used in film and video sound recording, and why it was taken up so enthusiastically by European broadcasters in the early days of FM stereo, plus M/S inherently makes mono-compatible stereo recordings; all you have to do to get mono is take the signal from the M microphone by itself. In your case, you'd get the mono by adding the L and R signals together (but use a mixer, bro--don't just parallel the output connectors; that's asking for trouble).

--best regards

Would the addition of a cable that reversed the TRS from one mic solve these issues???  Right now L is same on both inputs, if you reversed it on one, how would that effect the recording???

This is interesting, I've thought about running 4x mics > P2 and have wondered how I could do it...

Thanks, DSatz!

Terry

[yug du nord]

uncleyug, not quite. You've been combining the left output of stereo mike number one with the left output of stereo mike number two, and recording that combination as your left channel. You've also been combining the right output of stereo mike number one plus the right output of stereo mike number two, and recording that combination as your right channel.

As I've said now several times, you can forget about M and S--you were never handling those signals; they only existed inside the microphones. By the time the signals escaped and ran through the wires that you had access to, they were no longer M and S, but left and right.

I suck at drafting, but I may have to resort to some kind of drawing to show you what I mean. Please don't make me do that if you can get my meaning from words alone (except it look as if that's not working so well on one or two of these points).

I think I finally get it!!!  Seems rather simple now that I'm reading your most recent words!!!  Took a while for things to click......  but I think I actually heard my brain "click".  So there is no need for stick figures at this point!!!   Even though I tied you up with this question for a couple of days(sorry bout that)...  I hope you'll be around for my next "brain cramp" (as I'm sure I'll have one)......  you flippin' rock!!! +T

                                                        >>>Thank you for all the effort!!!<<<

[DSatz]

uncleyug, attached below is a picture of what I believe you were doing with your setup. The two "green" signals were going into the left input of your recorder, and the two "yellow" signals were going into the right input.

Since the microphone capsules were spaced a few inches apart, there would be interference between them at mid-high frequencies and above. At a given frequency, depending on the exact sound wavelength and its relationship to the distance between the mikes, the interference could either be constructive (adding), destructive (cancelling), partway in either direction, or at a few select frequencies, altogether neutral.

This type of effect is known as "comb filtering," because the combined response graph has increasingly sharp up and down spikes in it as you go upward in frequency, so the response graph starts to look like a comb of sorts. In general, people try to avoid that in recordings; it's why internally, your stereo microphones use coincident capsules in their design.

As I mentioned before, the composite left and right signals that you'd end up with would be symmetrical with respect to the center line between the microphones. So in terms of overall balance, the resulting recording might still be quite reasonable sounding, even with the comb filtering. But I suggest that you try using just one of your stereo microphones at a time sometime; it should be clearer and easier to listen to. And/or you could try a single, simple pair of directional microphones arranged just as you had your stereo microphones arranged.

--best regards

[Nick's Picks]

right...
its all covered pretty much.

the stereo jack output from the sony is ring (right chan) and tip (left chan).
who knows whats really inside that sony mic.  Likely there are 3 capsules.  all cards.  two of which are side address, simulating a figure of 8.  this is then matrixed internally by the mic and it outputs essentially an  XY stereo signal.

so if you had two of these mics and ran the "splitter" cable, but more like a "joiner" in practice...
youd get two left channels on the "one" left channel (at the end of the splitter/joiner cable) and two right channels on the single "right" section of the 3.5mm stereo plug.

now...if it worked...., and you got a signal..., it would be redundant infomation w/the differences produced by the physical location of each mic...

basically, it would be a mess.

hope that helps, if not at least a little bit.
love the graphics dsatz!

[yug du nord]

Thanks all around fellas...  +T to y'all for chiming in!!!  After a crash course on this subject, I find it rather surprising that only 1/100 (approx.) shows that I recorded over the years, in this similar fashion ended up with slight vocal distortion (Pork Tornado w/ Gordon sittin' in...  great show).  Never distortion on the music though.  On some recordings with this set-up, vocals are a bit "thin", but I always accounted that to using "cheap mics"....  poor frequency response!  But after all you guys have stated, I'm pretty pleased that the recordings came out as good as they did...  given the fact that these mics are not "pro" quality!  DSatz...  thanks for the graphic...  as well as all the tech knowledge......  and patience for putting up with me!!!  I can be a rather slow learner at times!    Greatly appreciated!!!                                                                                                                     

Truthfully...  I've thought about this scenario for a long time, and I've never even had the thought that the left channel from each mic was going to the left channel of the recorder...  and vice versa with the right.  I always figured that each channel of the recorder was picking up the full stereo signal from each respective mic.  But now things seem so clear!!!  The fog has lifted...  I can sleep well tonight...  no more brain cramp...  it feels so goooood!!! 

And Nick's Picks...  I know that you know your gear, as I've checked out your web site(nice site btw)...  so thanks for throwing in your 2cents!!!  And I always kinda figured it was a redundant set-up, but I still think that the recordings where I ran two of these mics sound a bit better than the recordings where I ran only one mic.  For whatever reason!  Probably cause I had convinced myself that 2 is better than 1.

                                                    >>>Thanks y'all<<<       

[Nick's Picks]

I dont know shit.  I just talk a lot.



but...
if you had a 3rd mic and recorder..then you would know if a "pair" outperformed a single.  a test you can't do w/the two of them.