2 sm57's and phasing issues

[guhlenn]

Is there a way to avoid phasing issues? I was really amazed at how bad it can make things sound LOL. i always just did the one sm57 thing. Now with one sm57 per speaker (i have 2x12"cabs) i thought i would be ok, since every speaker has it's own mic. Wrong. I know the theory, iwould like some practical advice. I also was thinking of the condenser and sm57 thing, but now i am a bit discouraged... Just keep searching for the right mic placement? or is there a trick? I would like to get it right during tracking....

thanks alot!

 

[boingoman]

Assuming that the mics are in phase to begin with, then yes, a lot of it comes down to placement.
There is something called the three to one rule. The distance between the mics needs to be at least three times the distance from mic to source. If the mics are 3" away from the source, they should be 9" apart to avoid comb filtering, which is the result of the out-of phase frequencies combining.

As the signals combine, certain frequencies cancel out to greater or lesser extent. When you look at a frequency graph of the two combined signals it is a series of peaks and valleys, like a comb viewed from the side.
This is a general rule. Depending on the mics you can get away with less, or might need more, depending on how sensitive the mics are and their pick-up patterns.

 

[boingoman]

Something else- I have run into cases where the speakers in a cabinet aren't all in phase. You can check like this:
Plug a speaker cable into the cabinet. While looking at the cones, touch a 9-volt battery to the connector, + on the tip and - on the sleeve. The cones should both move in the same direction, most likely out. Don't hold the battery on there too long, DC isn't good for speakers. If they move in opposite directions, reverse the leads on one speaker so they both (or all, if its a 4x12) move in the same direction.

 

[brich2929]

Your mics could be out of phase. If you are using a preamp you can try to switch the phase of one(assuming your preamp has that feature)...of course I'd check your cabs like the above post says first. You may just be hearing what's actually going on.

 

[guhlenn]

I have 4 mics and 2 of those cabs .I'll be trying stuff out. Thanks alot for your help.

I'll let ya know...

G.