Feb 22, 2008 02:49 pm Anxiously awaiting responses!
All right, why can't I ever get 2 mics in phase on a guitar cab?
Posted on Feb 22, 2008 02:47 pm
Tadpui
I am not a crook's head
Member Since: Mar 14, 2003
This drives me nuts. It's something that I've resigned myself to just live with and manually phase-align my guitar tracks during mixing. Pain in the butt. I want to start being able to put both an SM57 and either a SDC or LDC both on my 2x12 combo amp and get them in phase. But for some reason, no matter how long I mess with it I can never find that spot where I can't detect any comb filtering/phase cancellation.
My current technique is to put both mics in approximate positions, mute the condensor and just listen to the dynamic. Then I move around the dynamic until I find a good spot (we all have our favorite spots, mine is about 1" off the grill, a bit closer to the center than the edge of the cone, and at about a 45 degree angle from the interior of the amp towards the exterior). OK great, sounds good so far.
Now I mute the dynamic, unmute the condensor and find a pretty good spot for it as far as stand-alone sound.
Now I unmute the dynamic and WHAM, serious phase cancellation. OK, so I move it around for minutes, hours, days, eons...but I can never find that perfect spot where it truly sounds in phase. I can always detect some degree of cancellation.
What I end up doing is aligning the 2 signals in Cubase to where they're not only in phase, but in total sync. As if they were 2 mics in the same spot. It usually sounds good to me, but I would think that's kind of unnatural since the dynamic, which is considerably closer to the sound source, should pick up the sound and then the condensor should pick it up a bit later.
But even when fiddling with it in Cubase I can't get the phase to sound right unless I line up the tracks where they're totally in sync.
Any advice? Save me the agony of spending about 15 minutes per guitar track manually phase-aligning them!
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Feb 22, 2008 02:49 pm Anxiously awaiting responses!
Feb 22, 2008 03:30 pm Well, I don't know of any other way than to move the mic's around and find an optimum placement like you are doing. I don't think there is a magic bullet. How much are you moving the mics? Even a distance of 1 inch can make a difference. IMO you are doing it right by getting good tone out of each mic separately and then working on adjusting the placement.
Feb 22, 2008 03:48 pm I usually make pretty big adjustments, listening all the while for any brief moment of the "aha!" sound. But its just me in my studio so I have to move the mic with 1 hand while strumming the guitar with the other. But even while making these big adjustments, I don't even hear a brief moment where it sounds in phase.
It's especially painful since the 3:1 rule doesn't really apply due to the very small distance between the dynamic and the sound source. Having the dynamic 1" from the speaker would put the condensor at 3", which is way too close due to the high SPL at that distance.
Would the 3:1 rule extend to any multiple of the 3:1 distance? Like if mic1 was at 1" from the source, could mic 2 be at 3", 6", 9", 30", 150", etc. and still be in phase?
Feb 22, 2008 04:04 pm Quote:
could mic 2 be at 3", 6", 9", 30", 150", etc. and still be in phase?
My understanding is yes. I beleive it has to do with cycles per second and the sine wave. The cycles repeat at consistant intervals. The length of the cycle depends on the frequency. This is where it confuses me since a guitar amp has so many different frequencies.
Feb 22, 2008 04:10 pm Someone on reaper board just made a JS plug to do this automatically:
www.cockos.com/forum/showthread.php?t=18104
not much help, but i figured maybe it'd help someone else.
Otherwise, sorry, no help from me =(.
Feb 22, 2008 08:46 pm I've used a similar plugin, I just remember it was shaped like a ladybug or something. The trouble with it was that it introduced a slight amount of latency itself, so you'd have to load it up for all of the tracks whose phase you were trying to match.
That one looks better though, like its almost a batch kind of thing where you tell it which tracks to phase-align.
I guess I'm just looking for a way to get it right in the setup and not have to worry about phase during mixing.
I'll try the smaller adjustments and see if I can hone in on the sweet spot that way.
Feb 23, 2008 12:54 am This has been bugging me since you posted it . Your technique is spot on, and it seems it all should work fine . You've obviously tried inverting the phase within the software, as well, eh ??? .
Maybe the room is messin' with you ???
You might try an X-Y pattern with a couple of dynamic mics; 6"-24"away from the amp-face . Maybe even a dynamic and an SDC in an x-y...
Feb 23, 2008 01:19 am I don't know, maybe you've already tried this but I would use a clean signal from the guitar ie: no distortion, effects etc, and may be even a lower volume level to get the phase aligned then add the distortion/effects and make what ever slight adjustment might be needed.
Dan
Feb 23, 2008 06:34 am I don't think two mics can ever be in phase. Different frequencies have different wave lenghts, and they're not going to all hit the 0 degree mark at the same place, except where the source is. Also, once you move the two mics apart, there is always going to be a delay.
I remember reading about a guy who would find his sweet spots, records both waveforms, zoom in and then decide if the second mic needed to be moved backwards or forwards.
Also, the 1 mic in each ear of some good headphones gives you a good idea.
Oh yeah, and a technique I learnt from 'Clint Murphy', the head engineer at 'York Street Studios', Auckland New Zealand, is to grab a sustainer pedal, crank up some guitar unplugged white noise and run both signals into headphones. Lets you hear how the mics react at all frequencies. Cranking the amp max with no input should do the same thing. This technique works really well eh.
Feb 23, 2008 06:46 am BTW, you listen for when the white noise is the LOUDEST in the head phones. Loudest = more in phase, obviously :-).
Feb 23, 2008 08:48 am i know the **** ya going through with this mic thing, i tend to agree that you may never get em in phase, but i cant see why ya cant use the 6:1 ratio. or in multiples of 3.
here's something that i've thought of and yet to really have a good look at but, im thinking that there may be eq's making the phasing worse.
eventually i am gonna try messing with certain frequencies that i think may be making the whole thing sound worse than it really is. having totally different frequencies on 2 tracks, to make it sound like 1 track as a whole.
eg; one thinner sounding guitar with some freq missing and another guitar with the missing freq from the first in there. but trying never to double any 1 freq.
so without the 2 combined it sounds like turd.
Obviously they both gotta be panned around each other in the mix, but you'll have more control on what eqs you want heard in the mix coz you got one with higher eqs and one with other eqs, also you can sit them different volume wise creating depth, but its still only the one take so she nice n tight. check out the topic i put in "Mixing" under the art of mixing, its pretty cool.
then do the same for the other side pan wise.
It'll take a while to get it right i think, but i seriously think there are offending eqs with the phasing that can be eradicated. if the eqs arent doubled how can they phase?
if im dribbling tell me to go to bed, coz that's really where i should be right about now.
Feb 23, 2008 08:49 am Good advice from the colonel. Do you have a phase meter that you are checking it with or is it just by ear? I have tried the constantly variable phase box from Little Labs and it does have a definate effect on the sound but I couldnt really understand what it was doing and it is pretty expensive. You should be able to get the mics in phase by ear but if not try a different room.
Feb 23, 2008 12:33 pm Yeah, I think I agree with CS, different parts of the spectrum will travel at different rates, so there's always going to be a bit of discrepancy, I'd think.
heh, yet again, i'm no help =).
Feb 23, 2008 12:37 pm Quote:
Ummm... try using one mic?
Y'a know...
Feb 23, 2008 04:34 pm I wouldn't be going through all of this trouble if I had used 1 mic with satisfactory results ;)
Plus, when it comes time to mix, I love being able to select more condensor (more mid-range and room ambience) or more dynamic (more low-mids and bite from the speaker cone) on each guitar part to kind of tailor the feel of it.
I like the white noise suggestion and the clean guitar suggestion...they're kind of opposite ends of the spectrum but I can see each being easier than what I'm doing now. I have a sustainer pedal that really creates a lot of noise at extreme settings so I think I'm going to try that today and see where it gets me.
I do back off the volume as I'm positioning the mics, mainly because the wife, the dog, and the neighbors don't particularly enjoy Em7sus4 (6 open guitar strings) being strummed over and over at 100 dB :D
Thanks everybody for your suggestions so far, its given me a lot to chew on. Keep 'em coming if you can think of anything else to help out!
I really like these kinds of threads, it reminds me of the true spirit of these message boards.
Feb 23, 2008 04:48 pm Even one mic can be out of phase... just sayin'....
Feb 23, 2008 06:05 pm My left ear has been out of phase since 1977.
I'd rather not elaborate.
Feb 23, 2008 10:05 pm Colonel Sanders you're the man! Using my sustain pedal (and my TS9) as white noise generators is working extremely well! You're a genius.
I'm listening to different mic positions like a doctor with a stethoscope now :D
Feb 24, 2008 04:13 am Haha, sweet as man, just passing on the knowledge.
Feb 28, 2008 09:03 pm I've used up to 3 and even 4 mics on a cab. And I have to say aligning them is a two hour task. And even then I still end up re aligning the tracks most times. Even with two mics it can really be a pain.
But as stated you are approaching it the right way. But moving in small increments is the only way I know to do it. Sometimes it is side to side, other times it is forward or backward to get it close. It is as CS stated never going to be perfect unless you have the perfect room for it.
A distorted guitar is even harder to align then a clean one though so that is a major task.
I say don't give up, keep trying different positions for the amp as well as that is most often the key to getting them to align well.
Feb 29, 2008 01:16 am Quote:
A distorted guitar is even harder to align then a clean one though so that is a major task.
You're not just whistling Dixie there! I had it what I considered perfect with the preamp gain low and no overdrive pedal. But as soon as the pedal was clicked on it was an out of phase mess.
Even though the white noise trick has helped a ton, I've still had to manually align it in Cubase. It still sounds better to me in perfect sync rather than its natural delay between the close mic and the condensor, even if its in as good of phase alignment as I can get it by mic positioning.
I'm positive that this isn't the way the pros do it but damn I just can't seem to get it to sound good any other way.
I appreciate everybody's help through this, I've learned a lot from this thread!
Feb 29, 2008 02:16 am I've read that a few of the top dogs use phase as EQ. And the only time I've ever seen a 'pro' in action, he grabbed an SM7b and a U67, jammed them right up on the grill cloth of an AC30TB and used white noise to allign them perfectly. Took abut 20 mins. That was for a sort of indie pop / alternative rock band.
Oh, he also ran a CS3 in front of the amp. Not so great by it self but in the mix it sounded tops.
Feb 29, 2008 08:32 am Well the Colonel has it! Wave length = 345m/s divided by frequency. The audiable range of frequency has wave lengths varying between 17mm and 17m. Even if you "allign" the tracks in software, something is going to be out of phase and something will be in direct opposition or cancelation. Soo... I'm thinkin Mr. Tadpui that your ears are just super good! The rest of us seem to find spots that are pleasing to us for miking.
Now haveing said that; add the physics of how sound is despersed from a speaker cone and or multiple speaker cones, how a room will "resonate" to frequencies or cause them add in amplitude as they bounce around, how those bouncing waves hit the mike and YowZer!; you have got an inagima in terms of perfect phase allignment.
Conversly, part of how our brains precieve stereo is the delay between our ears (I'm old so I have a long one)or when our ears receive the signal.
Are you keeping each mic seperate in the mix, with a little space (panning) between the tracks? Sometimes this will help if you arn't already. Adds "fat" and a more natural dimension to the overall sound.
Mar 02, 2008 01:16 pm If you turn one mic out of phase with the other, you can move a mic around while playing until the mic signals cancel eavh other out and you hear nothing. Flip the mic's phase back and they should be in phase.
The room shape and size does effect the signal picked up by the mic, this can be detrimental depending on the accoustics of the room. You may want to try recording in a different space.
Mar 02, 2008 05:30 pm one trick to try is to set the mics for the MOST cancellation (thinest sound) then flip the polarity 180 degrees on one of the mics....try to get the worst sound possible....donno if it'll work, but it might be worth a shot.
Mar 02, 2008 07:21 pm Man, if we combine the white noise with the phase flip, we might just have the most baddass micing technique around!
Mar 02, 2008 07:41 pm If I remember right, you were running Cubase. I'm using Nuendo so, it's a long the same lines. But, at the top left of each individual channel strip there is that phase rev. button(ish) thingy. It saves me a ton when I'm just rushing to get a song idea out of me. But, I'm very anxious to try the white noise idea. Sounds divine. :)
I guess the point of this is, the phase reversal works well for me. :)
Mar 03, 2008 11:30 am I'll look for that phase invert switch in Cubase SE. I don't think that my mixer has a phase invert switch so i'll be dependant upon software to do this.
I'll probably be tracking more electric guitars later this week so i'll see if I can get this to work. I have a feeling that it just takes more patience than I've given it so far.
Mar 04, 2008 05:31 pm I don't know if this has been brought up but if you're trying to deal with a phasing problem, listen in mono. There will always be some phasing when you're dealing with distance. Having one mic of axis does not help the situation.
Mar 11, 2008 08:22 pm Hey there, Just my opinion but I think one of the reasons that your phasing gets all screwed up when stompin on the distortion box is that most overdrives derive their sound from clipping the sinals to a square wave instead of sine . This in turn creates buku harmonics, some at really wierd intervals like fifth orders and such.When you get a bunch of different harmonics going at the same time you will get a lot of cancellation at odd frequencies like you are talking about. What happens when you add distortion to the audio from the mics once you have them sort of phased? I know that's not the sound you are trying to achieve but I'm curious...
Mar 15, 2008 01:09 am In order to make phase cancelation evident the mic's must be at aproximately the same volume or in a level difference less than 6db, so try placing the mics where you consider they sound "less phasy" or closer to what you want and then try making volume adjustments between the two, leaving a 6-9db difference in levels between the condenser and the dynamic, this should give you a bigger sound with out the phase cancellation being evident.
In fact the 3:1 rule is based in this principle, the rule as many know (im not going to explain it) is designed to avoid phase cancellations, but its main principle is that the difference in levels between the two mics will be aprox. 9db so phase cancellation becomes inaudible, try using this principle in anything and it should give you good results.
Mar 18, 2008 01:09 pm "If you turn one mic out of phase with the other, you can move a mic around while playing until the mic signals cancel eavh other out and you hear nothing. Flip the mic's phase back and they should be in phase." -Kyle McSparron
This is the answer, btw. It lets you hear exactly what frequencies are being canceled out too, as anything boosted when the phase is flipped, will be cut when the phase is normal again.
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