Phasing - Guitar Amps w/ Multiple Mics

[dizzlano]

Hey all -

I'd like to know more about the fact that when I put say two mics right on a amp cabinet, and get them the distance, I don't have any phasing issues,,,,,,,,which is the point right?

But lets say add a third mic, maybe two to three feet off the cab to pick up more "true" bottom end. Now when mixed with the other two close mics, phasing becomes an issue, obviously because of the distance and time sound takes to get to the further mic.

Now should I be adding a small amount of delay to the furthest mic to compensate and match up the phasing with the two close mics?

Or....Should I leave it the way it is,,,,,and make that part of the sound.

I'm sure this is probably a matter of taste, but will this phasing issue,,,,,,,hurt me down the line when it comes to say summing the guitar tracks, and then mixing with the rest of the instruments?

Thanks in advance for any ideas or suggestions.

- Dano

 

[Son of Mixerman]

Just move the room mic until the phasing goes away or is nearly unoticable. Its now how many mics that are the problem, but its the distances of the mics from the source.
I know that Steve Vai uses 3 mics on the same speaker and then a couple of AKG414 or Neumann U67 room mics and just keep moving them around, and check it in mono to be sure.

pipelineaudio (Aaron Carey) did a excellent job in explaining the multi-mic phase problem. If you can't find it here he post at another website called http://www.recordingproject.com
and they even have a special place for his post on this very subject.

SoMm

 

[jdier]

Use some math, man. The sound will make a wave that goes up and down. This is over simplified, but make sure the far back mic is where the wave will be moving in the same direction as the waves picked up by the close mics. For instance if your first mics are 3 inches from the cone, your next mic back should be 9 inches.

If your close mic is 1 foot back, your far mic should be 3 feet.

It is a 3:1 rule. Again, I am over simplifying a bit, but that is basically how you fix your multi mic phase problems.

 

[dizzlano]

Thanks for the tip. I have heard of the 3:1 rule. Never got it till you simplified it even more. Believe me,,,,,,,its really not over simplified,,,,,,,,,,especially with someone like myself,,,,,,,who usually doesnt get things until they are laid out in laymens terms,,,,,,,lol

Thanks again my friend.

-dano

 

[mixsit]

Use some math, man. The sound will make a wave that goes up and down. This is over simplified, but make sure the far back mic is where the wave will be moving in the same direction as the waves picked up by the close mics. For instance if your first mics are 3 inches from the cone, your next mic back should be 9 inches.

If your close mic is 1 foot back, your far mic should be 3 feet.

It is a 3:1 rule. Again, I am over simplifying a bit, but that is basically how you fix your multi mic phase problems.

Uh...? Are you cross-pollinating?
I'm recollecting that the 3:1 rule is to keep a second mic picking up the same sound at a lower volume so it doesn't cause phase problems. If the second mic is brought up in volume, the distance will set which frequencies are cancelled and boosted.

At 'close + a few feet' there will be lots of phase-tone changes as the two are blended. On seperate tracks they can be mixed (or not) for huge eq effects.
Or place the second mic far enough back so the combing is more averaged out.
Wayne

 

[jdier]

Uh...? Are you cross-pollinating?
I'm recollecting that the 3:1 rule is to keep a second mic picking up the same sound at a lower volume so it doesn't cause phase problems. If the second mic is brought up in volume, the distance will set which frequencies are cancelled and boosted.

At 'close + a few feet' there will be lots of phase-tone changes as the two are blended. On seperate tracks they can be mixed (or not) for huge eq effects.
Or place the second mic far enough back so the combing is more averaged out.
Wayne

http://www.alexandermagazine.com/recordingeq/EQ/req0104/phasing.htm

 

[mixsit]

http://www.alexandermagazine.com/recordingeq/EQ/req0104/phasing.htm

Exactly. The example is for two mics picking up two diferent sources in close proximity out of trouble.
Rember that the 'wave' isn't one frequence. Even at 3:1 it's still combing (but at a lowere level) and only a few frequencies are ever actually 100% cancelled or boubled.
If we want the distant mic to be at a similar volume as the close mic we'll bring the far one up in volume and that cancells the 3:1 effect.
Wayne