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Portable Preamp with M/S ?

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tgos3:
used Sound Devices MP-2.  Similar to original MixPre, but M/S instead of L-C-R mike assignment.   Lundahl transformer inputs.  All analog. can monitor and output encoded or decoded M/S.  Can monitor decoded while outputting encoded.
uses AA batteries or external DC (oldest units with barrel/concentric ext. port, later ones Hirose)

mine has worked without probs for ~20 years.  I use eneloops or DIY modified wall wart.

https://www.sounddevices.com/product/mp-2/

sorry if this is a double post -- I don't see my earlier attempt.

DSatz:
joining the chorus, judging over headphones how a recording is going to sound over loudspeakers is completely impossible when it comes to the spatial aspect of things. Yes, for every M/S setup there is an exactly corresponding X/Y setup, but to make adjustments by ear with an X/Y setup you can (for example) spread the axes of the mikes farther apart, but with the equivalent M/S setup, the corresponding adjustment is exactly what? It would involve a combination of changing the M mike's pattern and tweaking the ratio of S to M gain in the matrix that you're using. And that's just an example (of an adjustment that I make all the time when recording X/Y or closely-spaced).

The point being, it makes little sense to commit to any particular M-to-S ratio during a live recording unless you have monitoring facilities that most of us don't get to have on location most of the time. So record the M and S channels directly, monitor them through a matrix so that you hear L and R, but matrix the actual recording only in post. Otherwise you have to matrix it twice (once to re-derive M and S from L and R, then once to go back to L/R stereo once you've decided what sounds best).

Also I just want to say that double M/S (where a third, backward-facing directional microphone is added to a traditional M/S pickup, and fancier matrixing is applied) gives a much wider range of possibilities than traditional M/S. In my experience with traditional M/S, for any given listening setup, there was only one M-to-S gain relationship that gave a plausible balance between the width of the stereo image and the amount of reverberation in the finished recording. Unfortunately that one control (the gain on the S channel going into the matrix) controls BOTH of the only settable parameters of the recording, interdependently. Double M/S breaks that dependency by, in effect, making the pattern of the forward-facing microphone variable "after the fact". It does require three recorder channels and a software plug-in (or a hardware solution would be possible, though the software approach is more versatile and it's $free).

voltronic:

--- Quote from: DSatz on June 22, 2021, 04:34:05 AM ---joining the chorus, judging over headphones how a recording is going to sound over loudspeakers is completely impossible when it comes to the spatial aspect of things. Yes, for every M/S setup there is an exactly corresponding X/Y setup, but to make adjustments by ear with an X/Y setup you can (for example) spread the axes of the mikes farther apart, but with the equivalent M/S setup, the corresponding adjustment is exactly what? It would involve a combination of changing the M mike's pattern and tweaking the ratio of S to M gain in the matrix that you're using. And that's just an example (of an adjustment that I make all the time when recording X/Y or closely-spaced).

The point being, it makes little sense to commit to any particular M-to-S ratio during a live recording unless you have monitoring facilities that most of us don't get to have on location most of the time. So record the M and S channels directly, monitor them through a matrix so that you hear L and R, but matrix the actual recording only in post. Otherwise you have to matrix it twice (once to re-derive M and S from L and R, then once to go back to L/R stereo once you've decided what sounds best).

--- End quote ---

+1 on all of this, and to what others have said above. To me, the biggest reason for using M/S in the first place is the ability to tweak the direct / ambient ratio in post. I also can confirm that you get a VERY different picture of this when using monitor speakers vs. headphones. My advice is actually to use both: Go with the monitors first to get your balance where you want it, but then confirm that your mix translates well via headphones.


--- Quote from: DSatz on June 22, 2021, 04:34:05 AM ---Also I just want to say that double M/S (where a third, backward-facing directional microphone is added to a traditional M/S pickup, and fancier matrixing is applied) gives a much wider range of possibilities than traditional M/S. In my experience with traditional M/S, for any given listening setup, there was only one M-to-S gain relationship that gave a plausible balance between the width of the stereo image and the amount of reverberation in the finished recording. Unfortunately that one control (the gain on the S channel going into the matrix) controls BOTH of the only settable parameters of the recording, interdependently. Double M/S breaks that dependency by, in effect, making the pattern of the forward-facing microphone variable "after the fact". It does require three recorder channels and a software plug-in (or a hardware solution would be possible, though the software approach is more versatile and it's $free).

--- End quote ---

I have always wanted to try this. If I understand correctly, the two directional mics function as a variable bipole, whereas in traditional M/S or Blumlein, the mid element is a variable dipole? The "singing guitarist" scenario described here is a pretty compelling argument for the flexibility of double-M/S.
https://www.soundonsound.com/techniques/double-mid-sides-array

Gutbucket:
Best to conceive of Dual Mid/Side as providing a "variable pattern Mid" I think.  "Variable bipole" is something of an oxymoron - if you vary it, it then becomes some other pattern than bipolar, AKA figure-of-8.

The key take-away with Dual Mid/Side is that it allows for independent control of pattern and X/Y angle. Whereas with standard Mid/Side those two things are always permanently linked - unfortunately with a relationship that is the opposite of the way we would prefer them to be linked.. which is why there is generally only one obvious point where the ratio between Mid:Side produces good stereo.

Dual Mid/Side solves that problem, at the cost of one additional recording channel and cardioid microphone feeding it.  Not a bad trade for the ability to choose any pickup pattern for each microphone AND any angle between them with complete independence.  "Any angle" really does mean that one can point the virtual microphones in any horizontal direction, backward as well as forwards. One can even point each side independently rather than having to keep everything symmetrical, providing a virtual rotation of the stereo array.  Point the whole thing farther to the left or right as necessary to best balance the stereo image.

Lots of options afterwards! Maybe too many for some.


--- Quote from: voltronic on June 22, 2021, 01:39:47 PM ---To me, the biggest reason for using M/S in the first place is the ability to tweak the direct / ambient ratio in post.
--- End quote ---

Except you can do that with ANY stereo recording, regardless of microphone configuration used.

Edit to clarify (see following posts)- Actually, you can tweak the Mid:Side ratio of any recording in post, regardless of microphone configuration used..  Just be aware that some recordings will allow for more adjustment than others without problems.  But even with coincident-stereo recordings which avoid those potential problems, changing the Mid:Side ratio modifies several stereo aspects at the same time, and because of that there may not be much range of adjustment where all aspects work well.  More fundamentally though, recording using Mid/Side alone won't really give you much useful control over direct /ambient ratio afterward.  Dual Mid/Side however can give you some control, essentially allowing you to increase ambience to taste (not so much the other way) based on the direct:ambient relationship present at the recording position in the room, as can other configurations with additional microphones that are dedicated to the pickup of ambient sound with attenuated pickup of direct-arriving sound from the front.

It's just that if you record Mid and Side separately you can do so in a better way without the additional steps required to get back to Mid and Side again.  And it tends to work best when applied to material recorded with a coincident or relativity close spaced near-spaced microphone configuration (rather, those configurations tend to allow a wider range of Mid/Side stereo re-adjustment before other problems arise).  It can certainly be tried on any recording and minor adjustments might be beneficial even with wide-spaced configs, perhaps to correct a hole in the middle.  Just keep your ears open for other problems arising while dialing it in.

voltronic:
^ Thanks for setting me straight on those points, GB.

I get what you mean about "variable bipole" being a poor choice of words. I was only saying that to differentiate between fig-8 in the sense that the front/rear directional mics in double-M/S are in phase, rather than out of phase as they are on a fig-8 mic, which is a dipole.

Has anyone seen double-M/S used for acoustic ensemble recording before? It seems like there would be a lot of benefits to it. Someday I hope to purchase a good fig-8 mic so I can try it out.

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