Dual Mic Guitar Phase problems....need solutions

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kiln_house
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Dual Mic Guitar Phase problems....need solutions

Post by kiln_house » Thu Sep 17, 2015 7:19 pm

I have been trying to fix a dual mic recorded guitar track which I think suffers from being out of phase...I either chose the wrong mics (at3035 at about 2 ft and a pro37 on grill) or misplaced the mics...but I am suffering from what sounds like flanging between the two mics...How can I fix this? I am all analog over here going from a tascam ts8 to an Otari 5050 half track via a 6 channel soundcraft board.
Do I need to buy a preamp or DI with a Polarity Inversion switch or is there another way to fix this?
Can you do polarity inversion on 1/4" cables or only xlr mic cables?
Thanks for help

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Post by ashcat_lt » Thu Sep 17, 2015 7:40 pm

You can invert polarity on TRS cables, but not (well) on TS. Flipping polarity via any method won't actually fix the comb filtering, though, only move the notches and maybe make it more acceptable. Could just as easily make it worse

The only way to actually fix it is to remove the delay between them. You could insert a small delay on the close mic to "nudge" it closer to in time with the distant mic.

Or you can minimize the damage by turning down one or the other until the comb filtering becomes less noticeable. That whole "3:1 Rule" which I prefer to call the "At least 9db Rule of Thumb"...

Or you could run one or the other through an all-pass filter like one of those IBP ("In Between Phase") things which will again only kind of help by accident, but actually quite often does.

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Post by kslight » Thu Sep 17, 2015 8:36 pm

Is using only one mic or the other an option?

kiln_house
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Post by kiln_house » Thu Sep 17, 2015 11:31 pm

Ugh both mics sound pretty terrible by themselves...but its a good performance captured so I am kind of stuck...what delay should I look at using? Would just a pedal delay work or is there a studio rack thing I need?

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Post by vvv » Fri Sep 18, 2015 4:17 am

Me, I'd use my one-size-fits-a-hella-lot solution and re-amp one of the tracks.

Before that - have you tried flipping phase on one mic?

Otherwise, you need a delay set at 100% effect to knock the close-mic track back howevermuch, (and record a new track copy of the original through the delay, or at least mix down with that delay on the track). And since yer all-analog, ya gotta do it by ear, so start at like .001 seconds and try adding by the thousandths. (That would be for a "pure" result - just adding delay and using it as a effect might help.)
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Post by Injured Ear » Fri Sep 18, 2015 6:40 am

So each mic on it's own sounds awful and the current combination of mics sounds awful. Why do you suspect that when the mics are combined in proper phase it will sound great?

It takes about 10 seconds to align a pair of guitar tracks in a DAW.
How long will it take you to fix this with the tools you have available?
How long will it take you to get tools that will enable you to fix this?
How much money will it take to purchase the tools to fix this?
How long will it take to do the guitar part over again and record it so it sounds good with one mic?

Old units like the MXR phaser (or was it the flanger? Can't remember) could be set to 100% wet with no sweep and you could insert it on a track to adjust the delay time in very small increments to fix comb filtering.

Otherwise something like an SPX-90 or a PCM-41 could be set with short enough delay times that you could use to dial in the appropriate amount on the near mic to time align it with the far mic.
(sound travels at 0.895706603 millisecond per foot if you want to figure out your delay time. You'll need something between 1 and 5 milliseconds of delay)

Alternately, delay the far mic even more and the comb filtering will decrease. The sound will approach a slapback effect but it might work. This might be a solution if you have a delay but the times simply don't get low enough to do time algnment.

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Post by Drone » Fri Sep 18, 2015 8:07 am

With the tools you have, you can pick whichever track sounds better, or if you hate them both, just pick one, run it to multiple channels on your board, and EQ the f**k out of them until it sounds great. Or chain it to different channels for EQ, run it to one channel, run that channel to another, etc.

Don't be afraid to overdo the EQ. :mrgreen:
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Post by kslight » Fri Sep 18, 2015 3:58 pm

In that case taking one and processing it by either EQ, reamping, pedals, etc is what I would do. I had some guitar tones I didn't love and I went back and ran the miked tracks (since I don't DI) through different OD, fuzz, and rackmount EQs and filters to make them more interesting, but I wasn't trying to correct a phase issue, just a boring tone issue. Still, couldn't make it any worse?

I'd forget about using both mics for this mix.

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Post by Nick Sevilla » Mon Sep 21, 2015 7:19 pm

kiln_house wrote:Ugh both mics sound pretty terrible by themselves...but its a good performance captured so I am kind of stuck...what delay should I look at using? Would just a pedal delay work or is there a studio rack thing I need?
My advice:


RERECORD THE PERFORMANCE AGAIN.


As the old adage says : Shit in, Shit out.

This will take the least amount of time. This time, please pay attention to where the microphones are placed, do a few small test recordings to confirm what is happening on the record side, and adjust as necessary.

START with only one mic, and make that one sounds GREAT.

IF you still think you need a second mic, then put that into play, and always have the first mic listenable as you place the second one, and move ONLY the second one until you have a sound combined that is the one you are happy with.

Cheers
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Post by drumsound » Tue Sep 22, 2015 11:12 am

Are the 2 mics recorded on 2 different tracks? Maybe one of those Little Labs or Radial boxes will do the trick. If its mixed to one track, you're probably fucked and should start over.

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Post by Recycled_Brains » Wed Sep 23, 2015 2:27 pm

If it's your own stuff and you can do it again, that's what I would recommend as well. The time it will take to fart around with making it sound better (and it will likely only sound a little better, but still not that great) could be spent just doing it again.
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farview
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Post by farview » Sat Sep 26, 2015 6:49 pm

Like everyone else said, if it sounded like crap in one mic, sounded like crap in the other mic AND sounds like crap with both mics, why did you hit record?

There are two ways to get rid of the comb filtering:

1. delay the close mic to match the far mic. About 1ms per foot of difference.

2. Pick the mic that sounds the best and turn the other one down at least 9db quieter than the other one. Basically, pick the one that is the most complete sounding and EQ it as well as you can, the figure out what it is missing and EQ that into the other one and add it in behind the main one.

That is a lot of screwing around to get something less half-assed. You would be better off recording it again once you get the guitar sound right.

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