#432729 - 09/29/03 02:10 PM
Tips on mic placement and avoiding phasing issues?
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RockNRoll
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Registered: 09/30/01
Posts: 92
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Hello,
First of all, I'd like to say thanks to all those that have taken the time to answer some of the questions I have posted here before...Wish I could offer some tips to others who are also in the similar situation of learning, to sort 'contribute' in a way...but I'm certainly not qualified to do so at the moment...Thanks again!
I have generally only used one mic when recording off a guitar amp. I may wanna try to use a condenser as a second mic backed further away from the amp, but don't know much about how it should be placed and how to avoid phasing issues later with the other dynamic mic placed close to the grill of the amp when mixing later on...
Does the condenser mic have to be facing at the same angle and at the same point as the dynamic mic or can they be pointing at 2 different spots? In what circumstance would I have to hit the invert phase button on my pre-amp for one of these 2 mics, or is this something that has to be done in any case when using more than 1 mic? If I don't hit the invert phase button for one of the mics, would I hear some phasing when tracking?
When mixing these 2 tracks later, if they are panned apart (even just slightly)...would that be enough to void any phasing issues? Or could they be panned even at exactly the same point as long as I have inverted the phase for at least one of the mics during the tracking process?
Thanks a lot!
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#432730 - 09/29/03 03:17 PM
Re: Tips on mic placement and avoiding phasing issues?
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Matt.Hepworth
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Registered: 03/13/01
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Well, you will always have phasing problems - sometimes it will accent the sound and sometimes it will hinder. I often run tracks with a close mic and a condenser (what was that rule of threes?) and I often pan them opposites in the mix. This makes a nice wide field. Of note though, I usually mic with condenser a few feet back and off the side of the amp, rather than straight on. That way it really captures what the guitarist thinks his amp sounds like.
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#432731 - 09/29/03 08:46 PM
Re: Tips on mic placement and avoiding phasing issues?
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where02190
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The best way to check phase issues is to listen in mono. While a guitar sound may be kewl in stereo, and msot of the world listens only in stereo, there are still alot of mono only tv's out there. should your tune make it to television, if you have major phase issues with a l/r panned guitar part, the guitar is simply going to go away.
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Hope this is helpful. NP Recording Studios Analog approach to digital recording.
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#432732 - 09/30/03 02:52 PM
Re: Tips on mic placement and avoiding phasing issues?
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Tedly Nightshade
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Originally posted by where02190:
The best way to check phase issues is to listen in mono. While a guitar sound may be kewl in stereo, and msot of the world listens only in stereo, there are still alot of mono only tv's out there. should your tune make it to television, if you have major phase issues with a l/r panned guitar part, the guitar is simply going to go away.
A good thing is to mix the two mics to isolation type headphones, in mono, and wear the phones while moving one mic until things sound swell.
Another really good thing is the Little Labs IBP phase adjustment box. Absolutely top quality audio gear, and you can get one for like $350 (IBP jr.). Then you can twiddle with it after the fact, and get it exactly right. Very, very cool.
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#432733 - 10/01/03 04:09 AM
Re: Tips on mic placement and avoiding phasing issues?
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Dasher
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All of the above are good advice. I'd like to add a reminder of the 3-to-1 rule: if the first mike is 1 foot from the source, the second mike shoul be at least 3 feet away, to minimize (not eliminate) phasing issues.
Dasher
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#432734 - 10/02/03 02:30 PM
Re: Tips on mic placement and avoiding phasing issues?
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RockNRoll
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Hmmm...interesting, so do those phase inversion switches you find on pre-amps or mics useful or are they generally not really utilized?
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#432735 - 10/02/03 07:17 PM
Re: Tips on mic placement and avoiding phasing issues?
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soundman_dup1
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Phase inversion switches are used when two mics are facing different directions from the same source. For example sometimes on an open back amp you might put a mic in front of the amp and then another one behind the amp. You would have to invert one of the mics to make it in phase with the other one. This is done with snare drums too. One mic on the top and one mic on the bottom inverted
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#432736 - 10/02/03 07:24 PM
Re: Tips on mic placement and avoiding phasing issues?
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McQ
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Registered: 08/17/03
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Originally posted by RockNRoll:
...(much snippage)...I have generally only used one mic when recording off a guitar amp. I may wanna try to use a condenser as a second mic backed further away from the amp, but don't know much about how it should be placed and how to avoid phasing issues later with the other dynamic mic placed close to the grill of the amp when mixing later on...
Does the condenser mic have to be facing at the same angle and at the same point as the dynamic mic or can they be pointing at 2 different spots?
In what circumstance would I have to hit the invert phase button on my pre-amp for one of these 2 mics, or is this something that has to be done in any case when using more than 1 mic?
When mixing these 2 tracks later, if they are panned apart (even just slightly)...would that be enough to void any phasing issues?
If I don't hit the invert phase button for one of the mics, would I hear some phasing when tracking?......Or could they be panned even at exactly the same point as long as I have inverted the phase for at least one of the mics during the tracking process?
- Phase is the measure of a specific point on a waveform relative to a specified reference point.
- Phase Shift is usually used to describe a change in a waveform's phase.
- Phase shifting will always occur when a signal is delayed in time.
- A comb filter is characterized by regular and periodic alternating peaks and valleys at various frequencies in a system's frequency response.
- A comb filter is created whenever a signal is combined with a delayed version of itself.
- In echoic acoustic space, signal delay is created whenever there can be more than one path between the sound source and the receiver (e.g., ear or microphone).
- In an echoic acoustic space (i.e., *NOT* an anechoic space), a large number of comb filters are naturally created whenever a source's original acoustic wave can combine with a reflected version of that wave. This occurs whether you are using 0, 1 or an infinite number of microphones.
"Phase" is not: a mystery, a stomp box, a monster or a four-letter word (it's five). It's a necessary part of our world that often mucks-about with our signal's frequency response. Just learn to listen and make adjustments in mic positioning according to what you hear and remember...There is no recipe or formula for this. You must learn from experience.
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#432737 - 10/03/03 11:10 PM
Re: Tips on mic placement and avoiding phasing issues?
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S. Cruz
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Registered: 10/21/02
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Here's my very unscientific way of doing this.
While the guitarist plays, put the first mic where it sounds great. Get a second mic. Use the phase switch on your preamp or console to switch it out of phase with the first mic.
Listening to both mics in mono on headphones, move the second mic around in the room until you hear the volume drop. Keep moving the second mic to the exact spot the volume seems to drop the lowest. Set it up exactly there.
Now flip the phase switch back to normal on the second mic and you are pretty close to a great in phase sound.
Works decently for me.
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#432738 - 10/06/03 04:26 AM
Re: Tips on mic placement and avoiding phasing issues?
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audiofreek
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Registered: 05/09/01
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S Cruz talked about using the phase switch to check phase,this is probaly the most common use for it.
Even if you can't move the mic while monitoring,you can at least flip the phase to see if it is destructive,or constructive.If it makes no audible difference,or the meters don't increase or decrease in mono,you are aprox,90 out of phase.This means you have a serious problem that cannot be corrected by phase inversion.
The nice thing about hard disk recording is that you can alter phase relationships by moving one,common source track a few samples in either direction to correct it.This is often done with muliple mics on a drum kit.Old school guys get it right to tape,because there was no other way.
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#432739 - 10/06/03 05:06 AM
Re: Tips on mic placement and avoiding phasing issues?
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patrox247
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Registered: 09/14/03
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I thought the "phase rule of three" refered to sexual experimentation with two chicks.
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#432740 - 10/10/03 01:31 PM
Re: Tips on mic placement and avoiding phasing issues?
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strat0124
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Registered: 04/03/01
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Originally posted by NE-One:
Well, you will always have phasing problems - sometimes it will accent the sound and sometimes it will hinder. I often run tracks with a close mic and a condenser (what was that rule of threes?) and I often pan them opposites in the mix. This makes a nice wide field. Of note though, I usually mic with condenser a few feet back and off the side of the amp, rather than straight on. That way it really captures what the guitarist thinks his amp sounds like.
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