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

[tINY]

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]

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]

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]

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]

-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]

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]

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]

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

[dropblacksky]

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]

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).

[Juan Carlos]

Hi, I'd like to record an electric guitar witha masrhall 80w combo.I'd like to use a dynamic SM-57 and a condenser SE electronics 2200A.I've read that this causes in phase problmes and I've found this topic.Can someone explain how to achive the best resoults and how to deal with this phase problems.I have a M-audio fast track pro and a studioi projects VTB1 preamp.

Thank you very much

Juan Carlos

[NeilEngle]

I will almost almost always move the mic before i flip the phase. My setup at home doesnt have any phase switches, So I would have to do it in the software. Since that is the case i use it to my advantage; if im tracking on and SSL what you record (phase wise) is what your stuck with. In software you can always change that later. So i focus on getting the best sound out of the two (or more) mics.

As long as phase is somewhat in check, i can just move the audio region back and forth untill the phase is the best its going to be... This does mess with timing and other factors, but if the movements are tiny, it can change the sound drasticly.

[NeilEngle]

well... on an SSL there are also ways around that but... ya... lol

[uncle duncan]

On electric guitar, I usually put a ribbon and a dynamic up near the grill cloth, on the same plane so they can both be used in the mix, depending on which sounds better. (Usually it's one dominant, with the other adding either shimmer or beef to the tone.) One close mic in front of the amp and one behind is also a good approach, but the behind-mic is super-sensitive to positioning, so you really need isolation headphones to get it in the right spot. Same with the front mic, actually.

Then I put a fig 8 condenser out in the room, but at a right angle to the amp aimed at the walls. The null of the fig 8 pattern picks up no direct sound from the amp. This means there will be no phase problems with the room mic. If the room mic is aimed at the amp, you have the distinct possibility that you'll be dealing with comb filtering, which may or may not sound good.

[GetUpfortheDown]

The 180 degree polarity reversal on most consoles and preamps are handy in most scenarios. The "listen and pick the best sounding of the two" is good, but if a signal is 90 degrees out of phase (or relatively close to 90), the reversal will not make much of a difference, if at all.

By the way, I use the same guitar micing method- a 57 and a R121, right on the grille, capsules almost touching. No phase issues whatsoever.

[vernier]

Use one mic.
'

[Steffmo]

Try this....

Flip the second mic out of polarity.

Move the mic until it sounds HORRIBLY out of phase. Flip the polarity switch back.

Seems silly....but I find that its easier to hear when the mics are really out, than really in.

[Wayne]

Originally Posted by Juan Carlos

Hi, I'd like to record an electric guitar witha masrhall 80w combo.I'd like to use a dynamic SM-57 and a condenser SE electronics 2200A.I've read that this causes in phase problmes and I've found this topic.Can someone explain how to achive the best resoults and how to deal with this phase problems.I have a M-audio fast track pro and a studioi projects VTB1 preamp.

Thank you very much

Juan Carlos

One of the best ways to get a handle on this would be to set up your pair of mics, perhaps with a track or someone else playing through the cab so you can listen in phones while you do this.

Start with both mics up close and about equal volume.
Equal distance is about as close to in phase as it gets.

As you move one back you will here directly the frequencies affected by the time and distance differences.
As you move the one mic back it's volume will naturally also decrease as will the depth of the phase combing.

The decision here is whether a given 'far mic position is going to be used in near-equal mix or pan combination where you hear and like the phase/tone combination, or use a different distance/time combo, or try to correct for the time difference.
The really deep combing effects you can hear can be nulled out quite a bit as you move out and away from the direct sound field and into the random room reflections.

There is not a point at which it will all be back in phase' again except at some frequencies. It's also why IMO putting the terms '3:1 and 'near-far mic technique' in the same sentence can be a pretty whack and misleading place to go.

[Juan Carlos]

Sorry, I don't understand rule 3:1.Suppose I place a dynamic one or two inches far from the grill cloth.Where the condenser for capturing room ambiance should go according to this rule in order not to have phase problems?

[Kyle S]

its only a problem ifit sounds bad. put onsome headphones and grab the mic and walk around the room with it.

you really need to decide how it going to be placed in the mix as you are micing.

[Kyle S]

to everyone on here having problems understand this:

dont let what you hear on gearslutz RESTRICT you from getting a good tone. I see all kinds of misinformation about phase on here and elsewhere. if it sounds good, use it. You would be surprised what makes a guitar stand out in a crowded mix.

To those of you just starting out, an entire day with an amp, 2 mics, and a guitar and some headphones is worth a years' worth of reading about phase on gearslutz.

There are way too many variables to have a solid rule of thumb for phase for all engineers/locations. The sound bouncing off the floor right below your mics is something to think about too.

[nosebleedaudio]

Also know that the phase switch has nothing to do with TIME, different frequencies will be in/out of phase at different distances.
Listen...
Move mic.
Listen...

[Juan Carlos]

Ok, thank u for your replies.Another question, does someone know how to hook up the fast track pro soundcard, to a xenix 1204FX mixer? is better to use a mixer during recording right??

[filin]

Originally Posted by Mosby

nad polarity

lol

[Flying_Dutchman]

Little Labs IBP

[Juan Carlos]

please, little help