Phase Question

[Farview]

When was the last time you recorded sine waves with 2 microphones?

The 3 to 1 rule is about attenuation.

 

[drummerdude666]

I was trying to help to explain using pretty pictures what phase cancelation was - i was not saying that you record sine waves. But by using a sine wave in the diagrams it gives a clearer view to people of why phase cancellation exists.

 

[ggunn]

With regard to the 'two spaced mics' examples (like in the link), being equidistant is agreeably your best shot at having things in phase. What I don't understand is the point of the 'odd integer' regarding favorable ratios.

It's feng shui.

 

[Farview]

I was trying to help to explain using pretty pictures what phase cancelation was - i was not saying that you record sine waves. But by using a sine wave in the diagrams it gives a clearer view to people of why phase cancellation exists.

That has nothing to do with the 3 to 1 rule.

 

[boingoman]

But by using a sine wave in the diagrams it gives a clearer view to people of why phase cancellation exists.

Unfortunately that site doesn't help with the idea behind 3:1, which is amplitude.

The theory is that you won't hear comb filtering from phase problems if one wave is about -10db from the other. Thus, place your mics so the sound you don't want hits the mic at least -10db from the source you do want.

Example: Two horn players, each miced up. A's horn bleeds into B's mic, and vice-versa. When you listen to both tracks together, the bleed causes phase issues. The bleed from A into B's mic causes his horn to comb filter, and the same for Bs bleed into A's mic.

Solution: Have them set up so the bleed is at least -10db from the desired source. If you are using the same mics on both of them, the 3:1 rule should help. If they are 1 foot from their mics, putting them 3 feet apart should work. If one guy is using a more sensitive mic, they will need to be farther apart to keep the bleed down.

That's why it doesn't work when micing a guitar amp near and far. You want to be able to listen to both tracks at the same volume. Since 3:1 helps with phase issues using amplitude, not some mathematical ratio thing, it won't help when you listen to both tracks at the same volume.

 

[drummerdude666]

That has nothing to do with the 3 to 1 rule.

Yes.. i know.

But people werent understanding why the 3 - 1 rule 'works' and when it should be applied. So i found that page to help people understand the basics of phase cancellation so that they can see why 3 -1 won't work on that close mic-far mic situation.

If people learn WHY phase cancelation exists - then instead of randomly flipping phase switches (which only inverts something 180 out of phase) and seeing which sounds best - they can understand whats going on, and how to treat the problem.

Its not a hard concept to grasp and yet its posted on thie forum almost every week asking about specific situations. Im 16 and it makes perfect sense to me - so im sure that EVERBODY on this forum has the capability to understand the physics behind it.

 

[lomky]

dunno about all this mumbo jumbo stuff, but if I have more than one mic on a source I make it mono and flip the polarity button, if it sounds better I leave it, if it sounds worse I flip it back.