Question about amp miking technique

E

ericlingus

New member
Here is an article i've read about miking an amp.

One mic is almost never enough, but with two or more, phase cancellation rears its ugly head. Nevertheless, we got a trick for that right?

Here it comes.

Put the guitar down. Make it make noise, or take the cable off and stick it on something that will make noise. This noise has to be stable and constant.... a fender strat's hum is perfect for this assuming it has some midrange harmonics to it.

Using your console's meters, bring that noise up to wherever your "zero" is. This will probably require a lot of mic pre gain so make sure your speakers are turned down. Don't let anyone touch the guitar or whatever the noise source is. Once you've got the signal to zero, mute the channel.

Next go into the room with the amp, and put your second mic about equidistant from the speaker as the first mic ... Be careful not to disturb Mic#1.

Back in the control room, bring Mic#2 up to zero.

Now, very importantly, pull Mic#2's fader (NOT mic pre) down to -infinity. Unmute Mic#1. Slowly push Mic#2's fader up towards zero.

If the volume at your final Left Right Mix buss on your console goes up, you need to flip the phase of Mic#2. If your console doesn't have a phase switch, make an out of phase cable. Just reverse pins 2 and 3 on an XLR, and make sure you label that cable so later on you don't screw up some overheads or something. Remember: if the volume goes up, flip the phase.

If the volume goes down, we can proceed... keep flipping the phase until the volume goes down when they are at their zeros.

Now pick up a bat, knife or gun. Whatever you are best with. Threaten anyone in the control room with it and say, "DO NOT touch that guitar! I am going to have headphones on at extreme gain levels and am risking it all so you can have a good guitar sound." Wave the weapon around menacingly until you are sure that they get the point. Kick them out and lock the door if you can't trust em... now is not the time for gags.

Go out to the amp with headphones on. You will hear a hiss or buzz or hum... make sure the hum in the phones is louder than the one you can hear directly from the amp.

Do not cough; you will blow your eardrums right into each other. Be careful of any noise that may be present.

Now, extremely carefully, move Mic#2 back and forth, left and right. Slowly. You should hear a whoosh sound, much like a flanger pedal would make.

The trick here is to find the spot where the least amount noise is coming out of the headphones. Keep moving the mic until you find it.

Have you caught the theory yet? We are looking for the spot where the two mics are the most in phase with each other. If one is phase flipped, then at the most in phase spot, they will nearly cancel each other out. Find that spot! Once you get it, take off the phones and go back to the console.

Turn both mic preamp gains all the way down. Put fader one at the unity position on your console. Play your guitar and turn up the mic pre gain until you hit zero. Now mute Mic#1. Now turn fader two to the unity position. Bring up mic pre #2 until you hit zero.

Unflip the phase on Mic#2 at this point so that both mics are in phase.

Unmute Mic#1 and mess with the faders. Those two faders now become the best EQ money can buy! Turn up one, then the other, experiment to your heart's content. Once you get a sound you like, buss them together and send em to a track... or keep them separate if you want some choices later.

Revel in your glorious new tone!






now when he says "Using your console's meters, bring that noise up to wherever your "zero is", does he mean turn the pre amp gain up until on the meter it says 0? I can't seem to get it exact. I don't have an external console. I mix entirely in cubase LE. I have a firebox audio interface and miking my amp with a 57 and an e609s. So I turned the gain up till it said zero on the mixer in cubase and then I muted it and did the other steps he said. I found out that the mics where out of phase because the final L&R bus went up instead of down when I raised the volume on channel two. He said I would need to flip the phase with a phase reverse switch which my firebox doesn't have. I have a plugin phase reverse switch so I used that. Will that do the same thing? Because I used it and the volume still didn't go down.He said keep flipping the phase till it does down. What's the point of keep flipping the phase? Does that mean just keep flipping phase reverse switch on and off? This is where I got stuck at. I just couldn't get the volume to go down. Could someone help me out with this? I'd really appreciate it. Thanks.
 
I'm sure Southside G or senor Rosario will have their two "drachmas" in there

sheesh I'll have to print that & experiment
 
First the bad news. because of the price of gas these days, I've had to raise my price to 3.50 drachmas. :eek:

ericlingus said:
now when he says "Using your console's meters, bring that noise up to wherever your "zero is", does he mean turn the pre amp gain up until on the meter it says 0?
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First off, it sounds like he's talking about an analog console and not a digital editor. The scales there are different and the gain staging is different. But I'd think that the basic theory should still work.

I believe what he's saying is that the output fader on channel one on the analog console be set to unity gain (i.e. "0"), and then you have to turn up the input trim until your noise gets to 0dBVU.

Things would be slightly different in the box. Ideally you'd set the track level in Cubase to zero gain (these would be the virtual equivalent of the console's faders) and turn up the preamps on your interface (the virtual equivalent of the console's trim controls.) Because of the A/D conversion, however, the gain staging can be a bit different and also the meters in Cubase are no longer reading analog VU, but rather digital FS. You aren't going to want or probably need to get each channel all the way up to zero, not only because you'll probably be boosting a lot of noise from your firebox as well, but also because when you sum the two channels togeter into your main mix, you'll probably be digitally clipping in the mix.

I'd say maybe find a level somewhere in the -13 to -9dBFS (+/- 3 dBFS) on your Cubase track meters. Whatever is loud enough to give you enough digital resolution without clipping and not so loud that you have to get a lot of hiss from your preamps. If theis combination means having to boost the track level in Cubase into positive gain, so be it. But you probably don't want or need to go anywhere near 0dBFS.
ericlingus said:
I have a plugin phase reverse switch so I used that. Will that do the same thing? Because I used it and the volume still didn't go down.He said keep flipping the phase till it does down. What's the point of keep flipping the phase?
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Standard Cubase has a phase inversion swicth available on each track. I'm not sure, perhaps LE doesn't. But if by a "plugin phase reverse switch" you're talking about real-time software plug-in, yeah, that should work.

If you're boosting to 0dBFS using Cubase's track volume, you might be having a problem with too much noise from your Firebox being boosted in Cubase that's just not being canceled by the phase inversion becauase the hiss is from two seperate preamps and therefore not identical. This could maybe be driving your levels up on you. That's only a guess on my part, though. Try it using the lower gain staging levels described above, finding the right balance in such a way where you don't have to crank your preamps too much.

The whole theory with the phase switching is this: When you have the phase reversed on ch. 2, when your summed signal of channel one and two maxes out, you have found a spot where there is phase cancellation, so that is a spot where you do not want to put your second mic. So he uses that spot to calibrate the metering and then has you move mic #2 until the summed signal drops out. That then tells you you have found a spot that is in phase and therefor theoretically sounds the best. So once you found that spot, you flip the phase on mic #2 back to normal and you should be set to go.

The technique is a little on the bulky side, perhaps - there are probably some shortcuts can can be used after you get the long version figured out - , but the theory is sound. Your not using an analog console does muddy up the situation a bit also. But with some practice and tweaking of the final technique I see no reason why it couldn't work.

G.
 
SouthSIDE Glen said:
First the bad news. because of the price of gas these days, I've had to raise my price to 3.50 drachmas. :eek:

G.
Click to expand...

in relation to the whole currency thing Mr. G.

The coin I was thinking of is a tetra drachmie that was around at the time of Alexander the Grape & apparently a soldier would've fought for 2 days in order to get this tiny little coin around 320BC

BTW this has nothing to do with micing a cab unless you taped the coin to the cone in the sweet spot for that extra metal effect

YEAH!!!!!!!
 
I just record stuff until I think it sounds good... I don't mess around with different amp micing "techniques" ":)
 
jndietz said:
I just record stuff until I think it sounds good... I don't mess around with different amp micing "techniques" ":)
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so every time you mic your cab you put things in exactly the same position without thinking "what would it sound like if??????????????"
 
slidey said:
so every time you mic your cab you put things in exactly the same position without thinking "what would it sound like if??????????????"
Click to expand...


Nope, I try other things :) I just never have the attention span to go and read these different techniques. I make it up as I go along ;)
 
if you're mixing ITB and can track each mic to its own track, then phase alignment is easily done post tracking.

it's basically the same thing and there are different methods... here's two

invert one track and slide it for minimum volume. then un-invert and slide for tone

slide one until you like the tone. phasing can be cool sometimes

the method in that article is a lot of work that is adjusted very easily post tracking in a DAW
 
Thanks a lot southside Glen and Keiffer. Keiffer, could you elaborate more on what you said? Are you saying once I record with the two mics, I zoom in on one of the mic tracks and move it back to match the other track?
 
yeah kind of...

you cannot always look at the wav forms and match them exactly. ears come first.

I may look at a transient and start there (zooming in) and aligning one track at a zero crossing or align the peaks. it depends. don't take this verbatim. this is only a guide and I possibly do it slightly differently each time. next I may listen and adjust using 1ms adjustments sliding one track until I get the tone I like. then I mix these two tracks to a virtual mono mix that I can select 100% one track to the other. these two tracks are then treated as one mono mix but physically remain as a stearo pair in the DAW.

I hope this helped...
 
maybe, maybe not...

i'm talking an adjustment of inches or less... where two mics are basically side by side or the same distance from the speaker.

if you have one mic close and another a foot back, then probably no...
 
yeah...

sounds travels at about 1115 ft/s, so a rule of thumb is one foot is about 1ms or slide it 1ms and that's close to moving the mic about a foot.
 
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