Phase issue with multiple mics - NOT typical 3:1 problem

[bkd_guitarist]

I'm using an SM57 and a Fathead ribbon mic to record a guitar amp into separate channels in ProTools LE. I understand the 3:1 rule to avoid phasing issues when recording with multiple mics, so I'm confused by the problem I'm having: with the SM57 an inch away from the grill and the Fathead about 3 feet away (36:1 ratio), I get significant phasing. When I move the Fathead closer, about a foot away (12:1 ratio), the phasing disappears. Reversing phase in ProTools doesn't help. What gives? Is there another side to the 3:1 rule, i.e. is it possible to have the mics TOO far apart? Am I just hearing the a delay associated with the time it takes for the sound to travel to the Fathead? I've read a lot of posts by guys who are using this setup, so I'm thinking it must be user error...thoughts?

[kludge]

Check the Fathead by itself. It's a figure-8, not a cardiod, and may be reacting to the room.

[bkd_guitarist]

Good thought...I hadn't thought of that particular problem, but I did check the Fathead by itself and it sounds fine. So does the 57. The problem only occurs with both mics on.

[louderock]

With 2 mics on the same sound source, unless the capsules are lined up next to one another, you will ALWAYS have a phase issue. It takes some experimentation to find which distance between the 2 mics will yield the best result. There will always be a certain 'honkiness' to the sound at certain frequencies. If you're using protools, one thing you can do is insert the time adjuster plug-in on the mic that is closest to the cabinet and adjust the delay time until you hear what you like.

The 3:1 rule minimizes this, but it's still there and noticeable.

[Greggy]

I've discussed this before, but this is why I only record with one mic per cab. Prefer multiple performances to multiple tracks/mics on one performance. The gainier the guitar, the greater the problem. That's been my experience. Also, I have found the 3:1 rule to be mostly beside the point with respect to cab micing. And as mentioned above, you can move the mics around and "improve" the result, but you will always have some phasing with 2 or more mics.

[louderock]

Find 2 different mics you like and put their capsules right next to each other and then blend the 2 mics to achieve the sound you like. This can work like an eq in a way. As long as the capsules are right next to each other, you will have no phase issues.

The other approach is to align the more distant mic with the close mic by visually looking at the waveform and moving the distant mic track to the left (earlier) to line up with the close mic.

[Greggy]

Originally Posted by louderock

Find 2 different mics you like and put their capsules right next to each other and then blend the 2 mics to achieve the sound you like. This can work like an eq in a way. As long as the capsules are right next to each other, you will have no phase issues.

The other approach is to align the more distant mic with the close mic by visually looking at the waveform and moving the distant mic track to the left (earlier) to line up with the close mic.

I've been meaning to use your latter suggestion. How effective is it? I guess I should try and find out. Thanks.

[mark norwine]

To begin with, is your basic polarity the same on both mics? i.e. pin 2 positive?

[bkd_guitarist]

Originally Posted by mark norwine

To begin with, is your basic polarity the same on both mics? i.e. pin 2 positive?

I'm not sure. I would have assumed it's standardized across XLR connections, but from the sound of your post that may be incorrect.

[bkd_guitarist]

Many thanks to all for some great input, Jeff in particular for the primer on phase cancellation! I've learned several new things today. TGP'ers are the best.

[wolf9309]

Unless you've changed it, they'll both be pin 2 hot. Almost everything is these days.

[MichaelK]

You already solved the problem:

When I move the Fathead closer, about a foot away (12:1 ratio), the phasing disappears.

...so who cares if another solution didn't work? That one worked.

The 3:1 "rule" is a good starting point for avoiding phase problems because they are more likely to occur if two mics are in closer proximity. But even then, they don't always occur. And following that "rule," as you discovered, is no guarantee that they won't occur.

No matter how you figure it, you're recording the same sound source in both mics, so they are the same basic waveform. Unless they are perfectly aligned (which they can never be, unless you've got the second mic in an alternate universe occupying the same space at the same time as the first) they will inevitably go in and out of phase to some extent, which is the whole point. That's what makes the wider, fuller sound.

But sometimes the out-of-phase seems to dominate and the combined result is a thinner, weaker sound than either channel solo. Sometimes reversing the polarity on one channel helps, sometimes it doesn't. And when it doesn't, you move one of the mics. Which you did.

That's what people mean when they suggest always checking for phase issues when using two mics on the same sound source. You could do the math, as Jeff suggested, or just stop when it sounds good, as you did. Congratulations on discovering the problem and doing the right thing!

[bkd_guitarist]

Originally Posted by MichaelK

You already solved the problem:

...so who cares if another solution didn't work? That one worked.

Sort of like when you go to the doctor and say, "It hurts when I move my arm like this," and he says, "So stop moving your arm like that." Yep, my post was not an urgent cry for help, more just a request for education on WTH might be going on here. Which I received, thanks to TGP'ers! I've learned more on this site in the last 9 months than in five years previously.

[MichaelK]

Originally Posted by bkd_guitarist

"It hurts when I move my arm like this," and he says, "So stop moving your arm like that."

Except in this case there's nothing wrong with your "range of motion." What happened was completely normal.

More like if you complained to your doctor about bumping your head every time you open the refigerator, and he says "So move your head out of the way."

[Sunbreak Music]

Some people are technical--their brains work that way.

Some are intuitive--they go by feeling.

If either way works, it's okay. It's rare to be both.