Questions About Phase Cancellation...

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Wannabe Producer/Tech Student
Member Since: Aug 11, 2005

I just have one or two questions about Phase Cancellation as i think I'm experiencing it.

Firsty, I'm micing up a 15 watt guitar amp with a 57 right up to the grill and a rode NT2A about 2/3 feet away. When i have recorded them, i get a kind of higher pitched weoring sound when i mix the 2 signals together, is this what phase cancellation sounds like?

I understand the physical justification of Cancellation and as such have tried moving the far mic around a bit to get it back in phase with the other, but i cant seem to avoid the noise - Ive moved it further away, closer, higher, lower, but to no avail.

The main problem is as im on my own, i cant monitor the sound, play the guitar and move the mic at the same time to try and get the mics in phase, which means that its very difficult to find the spot in which the 2nd mic needs to be.

any suggestions on how i can help this problem if it is Phase Canell. and if nots that, what is it?

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Eat Spam before it eats YOU!!!
Member
Since: May 11, 2002


Jul 16, 2007 07:50 am

are you sure the sound isn't already present in the Rodes track?

It could just be noise from the behringer mixer.

Prince CZAR-ming
Member
Since: Apr 08, 2004


Jul 16, 2007 10:09 am

like zek said: solo each track, is it present in one or the other?

I'm thinking it's not phase cancellation, if you've been moving them around. If it were, something would change.

Also, when in your computer (if you are), you can nudge one track slightly back or forward to phase align the two tracks.

Just zoom in to waveform scale, so you can see the two peaks. Move one until they both peak at the same time.

Done.

I'm guessing something in the room is introducing your noise. Maybe there's resonant freq with something in the room, and you can't tell until the two signals are added together. What in the room can resonate? cymbals, drums, tables, hard chairs, etc.

could be the amp cabinet resonating too.

i'm just guessing now =).

Also, headphones may help to find the problem, as will a freq analyzer, like voxengo span. Use that with a para EQ, and you should be able to hone right in on it, and maybe help excorsize your audio demons.

I am not a crook's head
Member
Since: Mar 14, 2003


Jul 16, 2007 12:28 pm

Since I'm the lone member of my audio engineering team, I have a similar problem with getting my guitar mics in phase. Usually I just end up getting it "close enough" and fix it when I sit down to mix.

Zoom waaaaay in on your 2 tracks and nudge one or the other over until you see a general pattern of the peaks and valleys matching up. See if that helps your comb filtering any (assuming that's what the problem is).

Most of the time I just end up scooting one or the other over until they match up perfectly (although I do realize that both mics didn't actually receive the signal at the exact same time).

Hold 'Em Czar
Member
Since: Dec 30, 2004


Jul 16, 2007 04:05 pm

yeah, you're definitely getting phase cancellation....what you're hearing is called 'comb filtering'

i'm with tad on zooming in and nudging the 57 track to the right....when you start to record...give a quick 'click' with a muted string and this'll work as a rock solid guide for re-aligning later.

don't try to fix it with eq, cuz you can't.

Member
Since: Jul 13, 2007


Jul 16, 2007 07:24 pm

As far as I've been taught and what I've had work for me is the 1:3 rule. Meaning when mic'ing a particular object try to have the 2nd Mic 3 times as far away from the particular object as the 1st mic. I find this method works best though of course this is just a rule of thumb and it will vary slightly depending on the mic and it's pattern but it's probably better to get it right in the front-end i.e. the recording than having to fix it in post.

Czar of Midi
Administrator
Since: Apr 04, 2002


Jul 16, 2007 10:08 pm

Yep, the only time that won't work of course is when close miccing a guitar with two mic's. But you can defeat the phase issues by simply taking a little time and moving the second mic around a little bit to find were they will work well.

edit0r
Member
Since: Aug 17, 2004


Jul 16, 2007 10:55 pm

White noise, boyz. Crank that amp to 11, slap on some headphones and find what positions make the loudest combined signal = most in phase. Equal energy at each frequency is much easier than trying to play and move those mics around.

Member
Since: Jun 02, 2007


Jul 17, 2007 01:58 am

whosyourdaddy00 said it best. It's comb filtering, sometimes it's good sometimes it's bad. I like to use comb filtering with 57's, but as everyone said, just line up the tracks in your DAW, when things are in phase you'll be surprised how good it sounds. Do this with drums as well. I make my drummer hit his kick drum once and the snare drum once before every song just to give me a good solid reference point.

www.rigsbysmith.com
Member
Since: Nov 13, 2004


Jul 17, 2007 04:39 am

1:3 always works with me as well. I spend a lot of time with a tape measure when tracking - especially drums.

Wannabe Producer/Tech Student
Member
Since: Aug 11, 2005


Jul 17, 2007 06:26 am

thanks guys for all the responses, alot of good info there. Will try all the stuff out and see how it goes.

thanks

Wannabe Producer/Tech Student
Member
Since: Aug 11, 2005


Jul 17, 2007 09:01 pm

yep, all sorted - tried the zooming in and moving it. worked a treat, can now mix the 2 signals together however i want without any of tht horrible noise.

cheers to everyone who responded :)

Member
Since: Jun 15, 2005


Jul 18, 2007 02:48 am

There is an article on recording electric guitar using 3 mics and keeping them all in phase and getting a great tone form your amp <a href="www.koretzmusic.com/rocksure2.html#tip11"> at this webpage</a> which you may find helpful. There is also a video on how to record electric guitar on the same page.

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