Out of phase: Move mic or use invert phase switch?

Joemamma · 14th December 2006, 09:46 PM

I was wondering how you achieve the best results when two mics are out of phase (e.g. snare or kick mics).

Do you move one of the mics until the mics are in phase and sound good, or do you just invert the phase on one of them?

Are there any important differences in these two methods?

tINY · 14th December 2006, 11:40 PM

If they are out of phase, you need to use the phase reversal switch. If there are path length problems, usually you get the best results from moving the mics around.

-tINY

zarembo · 15th December 2006, 12:14 AM

Quote:

Originally Posted by tINY

If there are path length problems,

hi tINY, can you please elaborate?

what do you mean by this?

thanks man

soupking · 15th December 2006, 12:18 AM

I think TINy's referring to the 3-to-1 rule. Where the distance of the mic to the object must be 1/3 the distance to a paired stereo mic setup. Also meaning that the stereo mics need to be 3 times the distance apart from the length to the source.

I think that's what he's talking about, like depending on what room you have to spare or distance from the source.

Led · 15th December 2006, 12:45 AM

I thought Tiny meant - if it's electronically out of phase (wiring issue) you need to use the switch. Otherwise move the mic. I would always do a phase check of all the mics anyway unless I was damn sure everthing was wired right. But if the wiring was all correct I would move the mic before i used the switch. Except for mics on the top and bottom of drums.

Wayne · 15th December 2006, 03:51 AM

-If there are path length differences they will be out of phase at some frequencies.
-Some of these less than in phase places sound better for a given situation than others.
-3-1 has nothing to do with setting or fixing which frequencies are in or out.

subatomicpieces · 15th December 2006, 02:54 PM

try flipping the polariity. then listen.

then, flip it back and go move the mic. then listen.

then, use the method that sounded better.

repeat anytime there are questions about phase relationships.

tINY · 15th December 2006, 07:57 PM

Phase is a problem at all frequencies if you wire a mic or speaker backward.

If you have a sound source - say a snare drum - and two microphones that are different distances from it, you will have phase cancelations at some frequencies (when the wavelength is 1/2, 3/2, 5/2, etc of the distance mismatch). This is called comb filtering...

The only way to avoid this for multiple sound sources (like snare and toms and HH) is to put the microphones right on top of one another - like MS or XY set-ups. The 3:1 rule and spaced directional mics can lessen the effect.

In the end, whatever sounds good is good....

-tINY

HEADROOM · 15th December 2006, 08:03 PM

Is it just a phase we re going through.....

dropblacksky · 15th December 2006, 08:09 PM

Since you most likely (hopefully) placed the mics with care and specific intention, I would definitely try inverting the phase switch first...if that doesn't help, then yeah, time to move the mics.

Mosby · 16th December 2006, 08:45 AM

Not to be a nag here, but phase is different then ploarity... sometimes they can be the same thing, or changing polarity fixes the phase...

The switch on your mic pre, that's polarity. One of the results of flipping this switch is that, the phase will be 180 degrees opposite from what it was. But that's a polarity adjustment that can, sometimes, correct a phase problem.

Phase, is more traditionally, a time based thing. For example, issues can arise when recording a bass guitar through a DI and mic'ing the cab. The DI signal will reach the "tape" quicker then the mic'd signal (remember, sound takes time to move from the cab to the mic). now the delay between the two signals will likely not be huge, but it is enough that one waveform will be "offset" from the other. This could cause phase problems in that they are not "in time" with each other.

I feel llike I'm bastardizing my explanation of phase nad polarity here, so I'll leave it at that. Remember, just because you mic'ed both the top and bottom of the snare, it doesn't mean that you have have to flip polarity. Solo both the top and bottom snare channels, and flip the polarity. Listen to see if the sound gets hollow, or if it gets more full. If it gets hollow that's a decent indicator that phasing might be at work. The reality is it might sound better with out the polarity flipped (or it might not - use your ears).

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14th December 2006, 09:46 PM	#1
Joemamma Gear addict Join Date: Nov 2006 Location: Copenhagen Posts: 467	Out of phase: Move mic or use invert phase switch? I was wondering how you achieve the best results when two mics are out of phase (e.g. snare or kick mics). Do you move one of the mics until the mics are in phase and sound good, or do you just invert the phase on one of them? Are there any important differences in these two methods? __________________ www.myspace.com/imhighhouse www.myspace.com/highhouseproductions

15th December 2006, 12:45 AM	#5
Led Lives for gear Join Date: Apr 2006 Location: Melbourne, Australia Posts: 1,812	I thought Tiny meant - if it's electronically out of phase (wiring issue) you need to use the switch. Otherwise move the mic. I would always do a phase check of all the mics anyway unless I was damn sure everthing was wired right. But if the wiring was all correct I would move the mic before i used the switch. Except for mics on the top and bottom of drums. __________________ "My voice has a built in extortion box" - recent vocalist I recorded...

15th December 2006, 03:51 AM	#6
Wayne Gear addict Join Date: Dec 2003 Posts: 326	-If there are path length differences they will be out of phase at some frequencies. -Some of these less than in phase places sound better for a given situation than others. -3-1 has nothing to do with setting or fixing which frequencies are in or out. __________________ Wayne Smith Long time part-time Monitoring at CathouseSound SP Tech Continuum AD

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14th December 2006, 11:40 PM	#2
tINY Lives for gear Join Date: Jul 2004 Location: Orygun Posts: 6,017	If they are out of phase, you need to use the phase reversal switch. If there are path length problems, usually you get the best results from moving the mics around. -tINY

15th December 2006, 12:18 AM	#4
soupking Lives for gear Join Date: Jul 2006 Location: Los Angeles Posts: 2,532	I think TINy's referring to the 3-to-1 rule. Where the distance of the mic to the object must be 1/3 the distance to a paired stereo mic setup. Also meaning that the stereo mics need to be 3 times the distance apart from the length to the source. I think that's what he's talking about, like depending on what room you have to spare or distance from the source.

15th December 2006, 02:54 PM	#7
subatomicpieces Gear maniac Join Date: May 2005 Posts: 244	try flipping the polariity. then listen. then, flip it back and go move the mic. then listen. then, use the method that sounded better. repeat anytime there are questions about phase relationships.

15th December 2006, 07:57 PM	#8
tINY Lives for gear Join Date: Jul 2004 Location: Orygun Posts: 6,017	Phase is a problem at all frequencies if you wire a mic or speaker backward. If you have a sound source - say a snare drum - and two microphones that are different distances from it, you will have phase cancelations at some frequencies (when the wavelength is 1/2, 3/2, 5/2, etc of the distance mismatch). This is called comb filtering... The only way to avoid this for multiple sound sources (like snare and toms and HH) is to put the microphones right on top of one another - like MS or XY set-ups. The 3:1 rule and spaced directional mics can lessen the effect. In the end, whatever sounds good is good.... -tINY

15th December 2006, 08:03 PM	#9
HEADROOM Lives for gear Join Date: Dec 2006 Location: HAMBURG Posts: 683	Is it just a phase we re going through.....

15th December 2006, 08:09 PM	#10
dropblacksky Gear addict Join Date: Sep 2006 Location: San Francisco, CA Posts: 407	Since you most likely (hopefully) placed the mics with care and specific intention, I would definitely try inverting the phase switch first...if that doesn't help, then yeah, time to move the mics.

16th December 2006, 08:45 AM	#11
Mosby Gear addict Join Date: Sep 2006 Location: Seattle Posts: 315	Not to be a nag here, but phase is different then ploarity... sometimes they can be the same thing, or changing polarity fixes the phase... The switch on your mic pre, that's polarity. One of the results of flipping this switch is that, the phase will be 180 degrees opposite from what it was. But that's a polarity adjustment that can, sometimes, correct a phase problem. Phase, is more traditionally, a time based thing. For example, issues can arise when recording a bass guitar through a DI and mic'ing the cab. The DI signal will reach the "tape" quicker then the mic'd signal (remember, sound takes time to move from the cab to the mic). now the delay between the two signals will likely not be huge, but it is enough that one waveform will be "offset" from the other. This could cause phase problems in that they are not "in time" with each other. I feel llike I'm bastardizing my explanation of phase nad polarity here, so I'll leave it at that. Remember, just because you mic'ed both the top and bottom of the snare, it doesn't mean that you have have to flip polarity. Solo both the top and bottom snare channels, and flip the polarity. Listen to see if the sound gets hollow, or if it gets more full. If it gets hollow that's a decent indicator that phasing might be at work. The reality is it might sound better with out the polarity flipped (or it might not - use your ears).