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Portable Preamp with M/S ?

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Gutbucket:
Yes, it is the manipulation of the level and polarity of the forward and rearward facing cardioids prior to their summing that creates the variable Mid pattern and determines if it is facing forward or rearward.

Used with the same polarity the resulting Mid pattern ranges between cardioid and omni.  Used in opposed polarity the resulting Mid pattern ranges between cardioid and fig-8.

DSatz:
Voltronic wrote:

> To me, the biggest reason for using M/S in the first place is the ability to tweak the direct / ambient ratio in post.

to which Gutbucket replied:

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

Well, yes, kinda sorta. You can certainly go through the same motions--deriving L+R and L-R signals, then rematrixing them in some other proportion. And that will vary the ratio of direct to reverberant sound in the recording. But if the recording wasn't made with a coincident main pair, that kind of adjustment will create comb-filter effects in both channels and screw up the whole high-frequency and upper-mid half of your recording, depending on how far apart the main microphones were and on how much you change the original proportions of your derived M vs. your derived S when you rematrix to L/R stereo.

The only way to make this kind of processing work without destructive interference between the channels is to start with a coincident main pair, whether M/S or X/Y. You have to decide in advance what your priorities are for a given recording. Do you want a groovy spacious feel in your recording? Then space your microphones apart at least somewhat. Or do you want the post-processing flexibility? Then use a coincident main pair (and record any spot or fill-in microphone signals onto separate recorder channels, so that you can blend them in after you've chosen your settings for the main pair).

But the sad fact is, you can't really have both at the same time, at least not in the way that I've always wished for. Double M/S, like Ambisonics, comes closer to giving you real post-processing options that work on the esthetic/feeling level--still not unlimited ones, but certainly less constrained than traditional M/S.

--best regards

Teen Wolf Blitzer:
I have a V2 with ms mod.  It's #13.  From Lucas Sound.  I would trade for a regular V2 (+) as I never use it.

Gutbucket:
Thanks for pointing out the potential problems.  To clarify a bit further..

I don't find a Mid/Side ratio adjustment of an existing stereo recording can "tweak the direct / ambient ratio in post" in any meaningful way.  However I do find it can be useful to make small adjustments in stereo image width and feel that can be beneficial.  In the end, its a tool that can be abused like any other, best approached with an ear open for potential problems as well as the potential benefit.  Notably, the same potential problems can arise with any other form of stereo post processing applied in a Mid/Side rather than Left/Right manor.  And yet such use is relatively common, as a mastering EQ technique for example.  But in that case the adjustment is typically minor and and comb filtering artifacts from it will be constrained to the targeted frequency bands.  As always, tread carefully and trust your ears.  Its post-work so you can always undo.

Gutbucket:
Here's the thing. Dual-M/S and ambisonics won't allow us to "tweak the direct / ambient ratio in post" in any meaningful way either.  Although I've not recorded using Dual-Mid/Side, from my experience recording with an ambisonic microphone I don't think either of those techniques provide a realistic way of doing that even though the separate control over pattern and angle they provide are very useful in other ways.  I did find I could often derive two acceptable stereo outputs for any one recording: typically a narrower angled pair of super/hypercardioids and a wider angled pair of subcardioids.  The two present significant stereo differences, and one might think they might provide significantly different direct/ambient ratios, but they don't.  All stereo combinations that work well end up with the same direct:ambient ratio.

This strikes me as somewhat analogous to standard Mid/Side where there tends to be only one matrix ratio that provides good balanced stereo qualities.  Similarly, with Dual-M/S and ambisionics there can be now several combinations of angle and pattern that provide good stereo attributes, but they will all tend to have the same direct/ambient ratio.

That's because control over the necessary third degree of freedom beyond pattern and angle is still missing, and that is the spacing between the microphones.  If we have control over spacing as well we can then trade angle for spacing to some degree while retaining a similar stereo image.  That does provide some control over direct/ambient ratio without overly compromising other important stereo aspects.

Pattern, angle, and spacing.  Dual-M/S and ambisonics provide for separate manipulation of the first two, but we need all three to apply the Stereo Zoom techniques and unlink imaging and other stereo qualities from direct/ambient ratio, so as to gain some useful degree of control over it, and even then the useful degree of control is limited. 

Extending the analogy drawn earlier even further..  We really need control over pattern, angle, spacing, and position, as recording position will always be the primary determinant of the direct/ambient ratio. 

TL:DR- Control over direct/ambient ratio is best achieved by choice of recording position.  If constrained to recording from further away than what would be ideal, using directional microphones and less angle between them can help somewhat, but then one needs to compensate with more spacing between them to retain good stereo qualities.  Control over pattern and angle alone in post won't do it.

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