polarity and gain relationships between mics

[okgb]

I use close mics together on a fairly regular basis, but the first thing I do is flip the "polarity" on one of the preamps and do very small distance adjustments until they sound as bad as they possibly can. Then I put the polarity switch back to normall on the one preamp. The two mics generally sound phase coherent after this proceedure...
_________________
-Patrick

matching levels with reverse polarity [ although not always 100 % cancelation ] is a decent way to make testing as close as possible .
I have been surprized how similar seemingly different things can sound
when the levels are closely matched .

And Pat has the " pultec " ear

 

[clintrubber]

[quote author="okgb"]I have been surprized how similar seemingly different things can sound when the levels are closely matched .[/quote]
Indeed! (levels & diaphr.position) I have only just put a quick ear to the soundfiles belonging to the article* from which the pics above are,
but I have a feeling that the surprise we're in for is more like 'is that all' :sad: than 'whoa, it really does matter way more than we thought so far' :grin: .

There's always of course the vibe involved, like drummers playing better when there's a cool-looking D12 and not an ugly D112 etc :wink:

Bye,

Peter

*: Sound On Sound, June '08

 

[okgb]

Another thing is the " frequency dynamics " of a given device ,
where as gtrs or drums or vox may seem to make preamps
& mics sound different not just because of the range they are played in
but how the mic & pres respond to those ranges . [ in level as well ]
something like a bright mic on a dull source vs a bright source
on a dull mic , or a flat mic with a mid heavy source vs the same source
with a scooped response , and of course this all varying over level
like the gtr getting fuller when hit harder

 

[rodabod]

[quote author="clintrubber"]

[/quote]


I have done something similar to this for vocalists before, prior to selecting the preferred mic.

The picture of the kick drum micing looks a little strange to me though - I'd prefer to move one mic around a lot.

 

[clintrubber]

[quote author="rodabod"]The picture of the kick drum micing looks a little strange to me though - I'd prefer to move one mic around a lot.[/quote]
I guess that's the point with shootouts like this one for instance: overwhelmed by the amount of available mics, facilities, nice gear & lots of time spent, you could get the warm feeling that everything is covered so conclusions on the subject can be made that will remain valid for the rest of your life - so subject closed, no need to re-consider, fully covered, just go by the conclusions*.

But despite all the effort etc, it's always easy to think of a few things that can alter the conclusions. Like you said, selecting a mic shouldn't be the end of it, next step is to search for the best position. It can of course very well be that 'a lesser mic' ends up being nicer when put at a different spot it was originally evaluated in. And then - how does it end up in the final mix.

Obviously an n-dimensional optimalisation problem, so complete control simply impossible.

BTW. as a nice contrast & sanity check there's an article in the same issue about a guy who often mics a drumkit with just one Shure-Elvis-mic

Bye,

Peter


*: I'm confident though that those conclusions will get the job done well enough most of the time.

 

[Guest]

It reminds me of a press conference, though no names of broadcasting companies on mics...

 

[burdij]

If the problem is appearing in the low end, its probably a phasing or wiring problem since for bass, even large separations will produce little change in the result due to the long wavelengths. Have you tried connecting the two mikes in series with one reversed in polarity to one preamp input? You will need to build a simple adapter with XLRs to do this. If the mikes are similar and correctly phased, you should get almost complete cancellation. If that occurs, you need to look elsewhere for the phase problem, like preamp wiring or badly wired mike cables.

You can do a simple mike phase test by setting your mike up in front of a speaker that is driven with a sine wave tone. Connect the electrical output of the amp driving the speaker to the horizontal input of a scope. Connect the output of the mike to a preamp input and the output of the preamp to the vertical input of the scope. Set the scope horizontal and vertical gains to produce patterns of approximately equal lengths with each input driven separately. Now, observe the Lissajous pattern produced for the reference mike and the test mike. If they are correctly wired and phased, the patterns for both mikes should tilt with the same or similar angle and direction. If the mikes are out of phase, one of the patterns will tilt in the opposite quadrants of the scope screen. The neat thing about this test is that you can do it at various frequencies.