tracking a guitar amp with 2 mics..

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drpfeffer

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Hi everybody..

I have been recommended using 2 microphones for tracking a guitar amp, insteaed of the "good 'ol single 57 trick" that has been my standard setup for tracking guitars.

And I can see what possibilities you get by using 2 mics on the guitar cab, but I need some inspiration on the use of the 2 recordings in the final mix. what do YOU do with the 2 recordings of the exact same guitar..? (make stereotrack? pan L/R? one track w/high volume and the other "hidden" in the background?)

Basically I just want to know some of the possibilities with the tracks, what do you do?

My setup is: JCM900 -> sm57 angled + ADK51s about 10cm. away on axis -> preamps ->DAW
 
A lot of people like a dynamic right on the grill cloth and a Large Diaphram Condensor backed up a few feet. You'll have to worry a bit about phase issues when you mix the two together. I prefer to work around this by nudging the room mic (LDC) track up a few milliseconds to counter the time delay caused by the extra distance (roughly 1msec per foot, but if yo have a DAW visually lining them up works better).
 
I concour with everything reshp had to say.

There are other 2-mic setups that can be used as well, depending on just what you're looking for: One example is using two microphones both on top of the grille. There are two variations on this setup.

One is to use matching microphones (e.g. two 57s), but to mic the cones in different locations. One might be angled in on the voice coil area while the other may direct on the outer inch or so of the cone. The idea is to grab the different characteristics of the amp - get the "accuracy" with the inner 57 and get more low warmth or low distortion with the outer one. Then blend them together to get a fatter sound than the single one alone. Because both are close-miked, as long as you stick to the 3:1 distance rule you should not have any phasing problems to worry about.

The alternative variation on this close mic scheme is to use two different mics instead of the same mic at two different locations. The idea here is to take advantage of the different characteristics of the different mics to get a more robust sound. Otherwise the same terms and conditions apply.

On the total other end of the spectrum is an extreme example of what reshp described: one close-miked dynamic and one far-miked condenser, but the far miked one is setup in such a way (by distance or direction or both) as to record the "room" as much if not more than it records the amp itself. This is akin to getting a natural reverb, which can be massive on some amped guitars and rooms.

All of these methods beg for plenty of expirimentation on mic selection ad placement (a one inc difference in close miked placement and make a mile of difference in sound sometimes.) Also, which technique may or may not work "best" totally depends on music style, guitar and amp type, room selection, and personal tastes. Figuring out that in itself can become a "black art". Take some off-the-clock time and expiriment and play around with the variations, and have fun doing it. :)

G.
 
SouthSIDE Glen said:
Because both are close-miked, as long as you stick to the 3:1 distance rule you should not have any phasing problems to worry about.
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Am I correct in saying that if he sticks up against one speaker angeled and one 57 up against another speaker straight on he will not have to worry about phase because the source is close miced. What about if these two 57's were on the same speaker?
 
thare is always the possibility of massive phazeing problems when multi mic'ing a git cab. a little less so with the one close, one room method, but still plenty possible.

it's really important to take time with mic placement when dual mic'ing a git cab because for every placement that makes it sound better thare are about 20 that will make it sound worse.
but it's worth the time it takes.
 
chadsxe said:
Am I correct in saying that if he sticks up against one speaker angeled and one 57 up against another speaker straight on he will not have to worry about phase because the source is close miced. What about if these two 57's were on the same speaker?
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I probably should have used a little less definitive wording. Giraffe is right, there is always going to be a danger of phasing problems if you're not setup right. The general 3:1 rule (that two non-coincident mics should be at least 3 times farther apart from each other as they are from the sound source) still applies, though the technical details here are a bit more complicated; things like different velocities between the inner and outer parts of the cone and such make that "rule" a bit fuzzier.

But if you are using a cab with large enough drivers - 10" or better yet 12" - and you are miking the voice coil and the outer edge, you can be quite OK if you make sure you're almost kissing the grille and not a few inches away. But you'll have to experiment to see what works. Giraffe is also correct that there are more ineffecive placements than there are effective ones.

I have sat in on many beer-and-pizza arguments over the dual miking a single cone vs. dual miking on two seperate cones debate. There are convincing-sounding pro and con arguments on both sides. While I have not done a whole lot of dual miking of this type myself, I have tried it both ways a few times and gotten mixed results. I once miked a Vox amp with 2 12s and got the best-sounding (for that session) results with a 57 on the voice coil and a Sennheiser 421 on the outer rim of the same element, but at a different session a Fender FM, also with 2 12s didn't sound right double-miked no matter what I did; on that one I was best leaving it alone with one 57 straight in on the inner third of the cone.

What I took away from those experiences were that the situation is always changing and unless you've got your own studio with your own stock of known amps (which I don't), you're never quite sure what will work best. You can have educated guesses - the next time I'm on one of those Voxs, I'm sure to try the same method again as a starting point - but you gotta be open to variations.

G.
 
I think his question is not so much how to mic the cabs but what to do with the tracks afterwards. I've actually wondered the same thing. Do you pan each hard L/R or blend them? Is there a standard method when using 2 mics?
 
hawk said:
I think his question is not so much how to mic the cabs but what to do with the tracks afterwards. I've actually wondered the same thing. Do you pan each hard L/R or blend them? Is there a standard method when using 2 mics?
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Lol, I missed that part too. There was another thread about multi mic'ing amps and I think I got confused.
Whatever works is the answer to the question. I like keeping the two tracks panned the same, in fact I'll make a mono submix of the two and treat the two sources as a single track. I usually double the part by replaying it, and maybe even use a different guitar/amp/mic combo and I'll pan the two takes L/R about 30/150 degrees.
That's what makes mixing so much fun, having all the tracks at your disposal to put together in anyway you like.
 
hawk said:
I think his question is not so much how to mic the cabs but what to do with the tracks afterwards. I've actually wondered the same thing. Do you pan each hard L/R or blend them? Is there a standard method when using 2 mics?
Click to expand...

A nice sound can be achieved by keeping the close mic centered, and then panning the distant/ambient mic to between 2 to 5 o'clock. You can also adjust the distant/ambient level to taste.
 
Hi everybody.. thanks for the replies..

Yes I was primarily asking for what to do with the tracks, after recording, but all the answers on the mic placing is also very useful.

Until now I have used a set of headphones for adjusting the mic placement, but I haven't used as much time on it, but I think I'm going to use a bit more time the next time I'm going to record (tomorrow) but thanks for all the inputs..

Still I would very much like to hear how you blend your double mic'ed tracks in the mix..
 
SouthSIDE Glen said:
The general 3:1 rule (that two non-coincident mics should be at least 3 times farther apart from each other as they are from the sound source) still applies,
G.
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The rule applies to dual sources, not a single source. It was devised to maintain phase integrity when micing close or semi-close by reducing leakage of the indirect signal pickup between two instruments. The 3:1 is also only the suggested minimum distance, 4:1 or 5:1 etc., is even better. Using an acoustic barrier as well as directional mics also reduces the leakage between the two soucres.
 
NYMorningstar said:
The rule applies to dual sources, not a single source. It was devised to maintain phase integrity when micing close or semi-close by reducing leakage of the indirect signal pickup between two instruments. The 3:1 is also only the suggested minimum distance, 4:1 or 5:1 etc., is even better. Using an acoustic barrier as well as directional mics also reduces the leakage between the two soucres.
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The 3:1 rule is usually incompletly stated exactly as you have stated it but that's not the whole story. It is also applied in variation to single sources in non-coincident setups. The idea with single sources is that the "middle ground" between coincident or near-coincident and 3:1 remains a no-man's land of stereo imaging of the primary source and potential phasing issues from secondary sources. When stereo miking a single source it in general remains as good an idea as with multiple sources to either go narrow (coincident etc.) or go wide (at least 3:1.)

G.
 
NYMorningstar said:
The rule applies to dual sources, not a single source. It was devised to maintain phase integrity when micing close or semi-close by reducing leakage of the indirect signal pickup between two instruments. The 3:1 is also only the suggested minimum distance, 4:1 or 5:1 etc., is even better. Using an acoustic barrier as well as directional mics also reduces the leakage between the two soucres.
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I think his point was that different parts of the speaker cone can be considered different sources.
 
reshp1 said:
I think his point was that different parts of the speaker cone can be considered different sources.
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Yes, in that case you are absolutely correct. The idea behind miking different parts of the cone is because they are generating different frequencies at different velocities and hence can be defined at this close of a range as being different sources. Of course you get just a few inches away and this distinction is blurred to the point of disappearing.

G.
 
phase reversing

Is phase reversing on one of the individual preamps for the mics a good idea, would that help me eliminate phase issues..?
(I'm going to record tomorrow..)
 
drpfeffer said:
Is phase reversing on one of the individual preamps for the mics a good idea, would that help me eliminate phase issues..?
(I'm going to record tomorrow..)
Click to expand...
No. The amnount of actual phase shift can be anywhere from 1 degree to 359 degrees. "Phase reversing", more properly called phase inverting, will help only with mirror-image phase offsets of exactly 180 degrees. This option is good mostly for bottom-miking snares and fixing reverse-wired cables, but is not intended for use on phase shifts caused by mic tchnique and environment.

G.
 
SouthSIDE Glen said:
No. The amnount of actual phase shift can be anywhere from 1 degree to 359 degrees. "Phase reversing", more properly called phase inverting, will help only with mirror-image phase offsets of exactly 180 degrees. This option is good mostly for bottom-miking snares and fixing reverse-wired cables, but is not intended for use on phase shifts caused by mic tchnique and environment.

G.
Click to expand...
OK.. thanks i'll lay off the phase reverse button..
 
Phase when using 2 mics generally has to do with DELAY, the time it takes the sound to reach the mic from the source. Different distance equals different delay. For a given frequency, this delay can be worked out to a phase. I.E. for a 1kHz signal a delay of .5msec = 180degrees, or exactly reversed phase. If you were to flip the polarity button, the two 1kHz signals would now be completely in phase. However musical sounds are never at any one frequency, but a spectrum of frequencies. For a given delay between two signals, they will fight at some frequencies (Destructive interference) and work together at different frequencies (constructive interference), if you were to graph the sum of the two signals over the frequency range, you'll see notches at a periodic frequency. This is called COMB FILTERING. So while flipping polarity can make one part of the frequency spectrum back in phase, you'll put another out of phase.

Subjectively, flipping the polarity might sound better because it moves frequencies where destructive interference occures somewhere less noticable for that particular sound, so don't shy away from that phase button.
 
reshp1 said:
I think his point was that different parts of the speaker cone can be considered different sources.
Click to expand...
Ah, that makes sense of it all. I was misunderstanding it and thinking he meant single speaker, single source. Thanx
 
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