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[Sandwell]

Hey guys, first post in the forum.
I've been wanting to learn abut getting drum mic's in phase for a while now. I've read a lot of articles about phase issues and the science of it all, but I can't seem to find any information about putting this all into practise when recording. Do you guys know any articles that can actually explain to me how to get mic's in phase when micing drums, or a book to buy that will? or could someone here be kind enough to explain it to me?
many thanks
Tom

[Jerome Malsack]

http://www.prosoundweb.com/article//in_the_studio_five_steps_to_checking_your_drum_phase_when_mixing/

http://www.prosoundweb.com/article//in_the_studio39/

http://www.prosoundweb.com/article//in_the_studio_avoiding_electronic_phase_cancellation_on_a_drum_kit/

[Fletcher]

You will never get every mic on a drum kit perfectly "in phase"... but you can start out with all of them in the proper "polarity" [a good part of the battle] with a tool from Galaxy Audio called the Cricket.  You put the speaker side in front of the mic and the receiver side in front of the control room monitor and look to see if the click registers red or green.  If it registers "green" you have achieved correct polarity... if it registers "red" I HIGHLY suggest you build some "polarity reverse" adapter cables [where pin 2 on one end connects to pin 3 on the other end and vice versa].

Most sounds we record have an asymmetrical wave form... pretty much every microphone amplifier I've ever met has a difference in level between the top of the wave form and the bottom of the wave form [and yes, this includes "class A" amplifiers which in theory should be symmetrical but for all intents and purposes -- even when properly calibrated -- do not].

Once that is done I usually bring up a few mics at a time and listen to their relationships [that's the "phase" part] in "one speaker mono" as that will give you a MUCH clearer idea of what is going on between the two [or seven] mics vis a vis phase relationships.

I hope this is of some assistance -- please feel free to post more questions if any of this appears to be ambiguous.

Peace

[Jim Williams]

Most sounds we record have an asymmetrical wave form... pretty much every microphone amplifier I've ever met has a difference in level between the top of the wave form and the bottom of the wave form [and yes, this includes "class A" amplifiers which in theory should be symmetrical but for all intents and purposes -- even when properly calibrated -- do not].

The waveforms may be asymetrical, but the mic amplifiers, whether class A or AB fed a symetrical sine wave will reproduce it that way. If not their THD specs would be way off. Some do 1.5 ppm, that's about as symetrical as symetry gets. Measure the top and bottom waveform on a scope, reverse one, overlay it and it cancels out.

[Fletcher]

While I grant you far more experience than I have in such matters Jim... I beg to differ.  I have looked at a plethora of Class A pre's on a scope and have never seen a one that is 100% symmetrical in terms of amplification of the top and bottom of the wave form.  At first I thought it was me that was fucked up... but the more I looked at the more I experienced the phenomena.

It all started when I was checking the bias on the B283 card on a Neve 1064 -- I noticed that the top of the wave form had a tad more gain than the bottom of the wave form at the best of times and was WAY out of skew when the bias was improperly set.  From there [for shits and giggles] I started to look at the output of a bunch of different "class A" [as well as "class A/B" and "class B"] pre-amps.  I understand the associated theories and was quite taken aback when I saw the discrepancies [though they were indeed minor - they were discrepancies none the less] and thought that perhaps my scope wasn't a happy camper... so I switched to another scope that had just come back from "maintenance and calibration" from Tektronix and got the same result.

I will grant that my sampling is absolutely too small to be considered "scientific Gospel"... but since that "discovery" I have found a palpable difference when using "polarity reverse" cables vs. the polarity reverse button [which generally sits on the output of the input stage of a microphone amplifier].

This experience is the basis for my comment -- I do NOT make ANY representation that my knowledge / skill set in these matters is even close to yours [like not even "sales tax"] and mean absolutely zero disrespect to you or your assertion... just sharing my personal experience and what I have heard [or perhaps think I've heard] over the last few years I was actually sitting "in the chair".

Peace

[Jim Williams]

1960's era single ended power class A circuits like Neve with variable bias are not representative of a modern mic or transistor amplifier's characteristics. Moving bias up and down will press one side of the waveform up against the rail or ground causing that peak of the waveform to change amplitude.

Any visual mismatch of a symetical sine waveform seen on a scope will measure around 3% THD in an analyser like Audio Precision.

3% THD would be desirable for many modern pop/rock productions, just not my cup-o-tea. I don't like my food chewed for me. Modern, well designed mic amps do not have that situation.

[Fletcher]

I'll have to take your word for it Jim... then again, I know your word is good so its not a great leap of faith on my part.

Peace