mikin guitar amp w/close and far mics. phase issues? and more...

[thecugga]

Hi, im about to record my bands demo so im asking any last minute questions before i go in there. This ones about the use of a far mic on a guitar amp.
First of all, I am using a SPB1 as a far mic for the amp, and it has never sounded good unless it is close-miking a quiet amp ... but anyways
Oh ya ... and the amp i am recording is a marshall (dfx250 i think) with dual 12s...also i will be using an e609 and maybe an i5 to close mic the amp.

1st question: i have read that an LDC can be damaged when close miking an amp. How far away should an LDC be from a fairly loud amp to avoid damaging the mic?
2nd question: are phase issues more prominent when the difference in distance between the close mic and far mic is smaller. in other words, the further back i move my LDC from the amp the less chance that phase issues will come up? is there a distance when you can be 99% sure that phase issues wont be a problem at all?
final question: I find that I have to keep the far mic fairly quiet in the mix, only using it to make up MAYBE 5 or 10% of the total guitar sound...more so just to give the guitars the smallest of a new dimension in their sound. the more i use of this mic the worse the guitars sound. is this generally correct with a far mic on an amp? the ol' "less is more" cliche?

sorry for the 20 questions ... if anyone can help me out at all that'd be great ... thanks alot

 

[BeeF DriPPings]

i use ldc mxl 990 to mic a cyber twin with 2 12s at 1-2 feet. i guess it depends on how loud you set the amp. experiment and figure it out for yourself

 

[thecugga]

first of all, i have experimented a ton with using a close and far mic and ive never gotten anything ive liked at all from the far mic ... but it seems general practice by people around here so i figured i'd ask some questions, find out where im going wrong
2nd, im not gonna experiment with how close i can put my ldc up to the amp before it blows.
3rd, because of this im using it at like 5 or 6 feet away from the amp. sounds bad. is this too far away? then, when i slowly bring it up under the other track it sounds like there are phase issues between the two. although, ive tried many different positions and it always sounds phasey with the two, im starting to think its just being caused by a shitty sound comin from the LDC and not phase issues at all.
also theres that 3to1 or 4to1 general rule of thumb for avoiding phase issues. so i thought having one close miked and one around 5 feet away would almost completely eliminate phase issues, in which case it IS just the sound comin from the LDC that sounds bad and ISNT phase issues at all...

this is WHY i asked this question. AFTER EXPERIMENTING for a long time and getting stuck on the same few things ... thanks tho

 

[metalhead28]

There is no magic distance that will assure a lack of phase issues. (maybe at extreme distances, I don't know).
The point I'd like to make is that plenty of people use nothing but close micing. I use only close micing for heavy sounds. Nothing says you need to use that distant LDC.

 

[VesuviusJay]

This may help...
https://homerecording.com/bbs/showthread.php?t=182533

And this as well... I know I've posted it many times, but it is one of the gems I have found here!

I done quite a bit of work for artists on the " Metal Blade " label so I guess I can chime in

Actually a lot of this came from following around the UBER God Of Metal Engineering : Bill Metoyer. ( check the back of your records, if you dont see his name on anything, you need a trip to the record store )

Make DAMN sure your guitar is in tune, and intonated properly. Different intonations and even VERY slightly different, can make whole separate flavors of distortion so get it as close as you can. If you know the difference in distortion sound between a 24 3/4" scale guitar neck and a 25 1/2" one then you know what Im saying.

Now on to your preamp, or preamp section of your head, depending on what you got. In most cases, metal guitar tones come from a LOT, a WHOLE LOT less ( thats right LESS ) distortion/preamp gain than you would use live. For riffs and chord changes, the REAL heaviness comes from dynamics, the fact that it gets LOUDER when your pic hits the string than when the string is just resonating.
It seems obvious but its not really. You need to MAXIMIZE the dynamic range at this stage because from here on out, the signal is going to be compressed and degraded in all sorts of ways. In most cases the gain should be about where, when if you SOFTLY strum a chord it actually comes out clean. Transistor amps/pedals may not do this ( some will ) which is another reason tubes are usually perferred for this type of thing.
Now, tone. Scooped mids, cranked bass and treble right? WRONG. For recording you will need a LOT more mids than you normally would for live. You need to be heard. The way our ears work, we take most of our cues from the midrange. Get as much body in the tone as you can....not bottom, body. You can always scoop it out later if you must. Like the lumberjack says " always cut long" right ?

Ok, on to the power amp or the power section of your head if you use one. Here is where you start the dynamic reduction process. You want to get a sound with enough sustain to work, but being careful whether or not you want to HEAR power tube saturation or speaker distortion. In some cases you want to, in some cases you dont. Get a good sound that you ENJOY. Make sure ( if you can at this point in the recording) that it fits with the other tracks. You will probably use a speaker that you wouldnt like live for this process. A speaker with more mid's than normal, like a celestion Vintage 30 or maybe a Kendrick. Greenbacks are good live, but sometimes lose that all important midrange on tape. Watch the speaker distortion, get a power level that makes COMFORTABLE dynamics for you. Errr on the LESS compressed side so you gotta work just a WEE bit harder than normal to crunch it up.

Now, stand in the room with the amp. Get your head moving around until you find the one speaker that sounds better than the others, or maybe just a real good spot where it seems to sound best. I am assuming we are NOT going after a " room " sound at this point. Stick a 57 RIGHT there, where your ear was.
Now, at the console, FIRST verify that that is *roughly* the sound you heard out there. Be sure levels are where they should be etc...no eq at this point on the console. Have someone move the mic back towards or away from the cab ( or do it yourself with headphones ). You are doing two things with this:

1) changing the ratio of direct( from the speaker ) vs. reflected ( yeah you might be only a few inches from the cab but the room still is playing a HUGE part) sound coming into the mic

2)changing the amount of dynamic compression that the actual volume of the speaker is causing in the mic's diaphragm, ribbon or voice coil. You are changing the BEHAVIOUR of the sound here.

Once you like the placement of your mic, its time to get REAL tricky.

ONE mic is almost never enough, but with two or more, PHASE CANCELLATION rears its ugly head. But we got a trick for that right?

Here 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. DONT let anyone touch the guitar or whatever the noise source is. Once youve got the signal to zero, mute the channel

Next go into the room with the amp, and put another mic about equidistant from the speaker as the first mic is...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 LeftRight Mix buss on your console goes UP, you need to flip the phase of mic #2. If your console doesnt have a phase switch, make an out of phase cable. Just reverse pins 2 and 3 on an XLR, and make DAMN sure you label that cable from now on so you dont 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 gonna 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 cant trust em...now is NOT the time for gags.

now 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. Becareful 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, much like a flanger pedal would make.

The trick here is to find the spot where the LEAST noise is coming out of the headphones. Keep moving the mic you will 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 got it, take off the phones and go back to the console.

Turn both mic preamps 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 2 to the unity position. Bring up Mic pre #2 until you hit zero.

edit : OOPS!!!!!!
I forgot, tho you prolly figured it out. Unflip the phase on mic #2 at this point so that both mics are IN phase. Sorry about that

Unmute #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 got a sound you like, buss them together and send em to a track...or keep em separate if you want some choices later...

revel in your glorious new tone!

Aaron Carey
StudioZ/Pipelineaudio
www.studiozpro.com

 

[metalhead28]

Yeah, you do post that alot! haha, you must have it on stand by or something.

Seriously, that technique would be pretty tough when dealing with two very different mics at very different distances. Basically there is going to be some phasing somewhere in the sound spectrum with a distant mic. You can minimize it or even make it work for you, but it will be there. Sometimes the specific phasing that you get will be what you like about the sound.
When dealing with a close and distant mic, the phase issues will not pronounce themsleves as it would with 2 57's equidistant from the speaker. Anyway, don't rule out close micing only. Especially if you're after a "heavy metal" tone.

 

[SouthSIDE Glen]

1st question: i have read that an LDC can be damaged when close miking an amp. How far away should an LDC be from a fairly loud amp to avoid damaging the mic?

By definition, the anser to that question is, "It depends upon how loud the amp is." I'm not being trite, here. The only way to give an accurate answer would be to measure the SPL of the amp at a certain loudness, and then place the mic at a distance where the SPL is 80% (margin of error, transients) of the maximum rated SPL of the microphone. But then there is no guarantee that it's actually going to sound any good at that distance; you might have to move it farther or nearer to get the right "sound" - and of course nearer would not be a good idea for safety reasons.

There are two recommendations I would give here. First would be skip the condenser and go with a dynamic. If that's not an option, then number two would be go with a condenser, but use lower volumes on the amp.

That second recommendation on lowering the volume is actually often a good idea regardless of the mic type. For a few technical and psychoacoustic reasons a guitar amp can sound better live at higher volumes, but sound better recordd at lower volumes than that.

2nd question: are phase issues more prominent when the difference in distance between the close mic and far mic is smaller. in other words, the further back i move my LDC from the amp the less chance that phase issues will come up? is there a distance when you can be 99% sure that phase issues wont be a problem at all?

Too many variables involved with things like room size and reflectivity to give an accurate answer here.

final question: I find that I have to keep the far mic fairly quiet in the mix, only using it to make up MAYBE 5 or 10% of the total guitar sound...more so just to give the guitars the smallest of a new dimension in their sound. the more i use of this mic the worse the guitars sound. is this generally correct with a far mic on an amp? the ol' "less is more" cliche?

That sounds fairly correct. The main purpose to a far mic in this instance is to pick up "the room"; i.e. it's a form of natural ambience recording. Just as in real life where the most of the sound your hearing is from the amp itself, and the rest is "coloration" added by the room (unless you're outdoors or in an anechoic chamber), the same should be true of your recording.

i have experimented a ton with using a close and far mic and ive never gotten anything ive liked at all from the far mic ... but it seems general practice by people around here so i figured i'd ask some questions, find out where im going wrong

You're not necessarily going wrong anywhere. There are several other possibilities:

- that micing technique is not suitable for your music and arrangement style.
- that micing technique is not suitable for your particular guitar and/or amp sound.
- your current room and/or room treatment is not conducive to good far miking results.
- your microphone selection is mis-matched to your amp and room.
- that technique simply yields results that aren't to your tastes as much as they are to other peoples tastes (I personally have no need or desire to far mic a guitar amp 99.9% of the time.)

The bottom line is keep expirimenting with different techniques and placements, keeping condensors at least a couple of feet off of loud cabinets to be safe, moving them in only when the amps are turned down to decent listening levels. Stick with the techniques you like, drop the ones you don't. That is really the important right/wrong here.

G.

 

[Hi_Flyer]

This may help...
https://homerecording.com/bbs/showthread.php?t=182533

And this as well... I know I've posted it many times, but it is one of the gems I have found here...

This is an interesting topic to me, as I have recently tried recording some guitar cabinets with a pair of dynamics. Now I didn't do all of the stuff that Vesuvius Jay describes, with the headphones and the phase and the hum... I sorta guessed with the mic placement, but I think I got lucky. I figured to avoid phase issues, I could play it safe by keeping the mics the same distance from their respective speakers in the cabinet. I put them maybe six inches from the grilleclothe, angled slightly into the side of the cone, not pointed at the center of the cone to keep out the fizziness...

Anyway, the peaks of the recorded waveforms line up perfectly, so I assume that means I eliminated most of the phase issues... But what blew me away was the sound when you combine the two tracks!!! Compared to anything I've ever recorded with a single mic, it was so much more like the sound out of a real speaker cabinet!

Sorry if this seems like an attempt to hijack, but I figure my experience is relevant to the topic...

Can anybody comment on what I'm doing? I feel like it was one of those Eureka moments. I'm not sure what I'm hearing though.

 

[mixsit]

2nd question: are phase issues more prominent when the difference in distance between the close mic and far mic is smaller. in other words, the further back i move my LDC from the amp the less chance that phase issues will come up? is there a distance when you can be 99% sure that phase issues wont be a problem at all?

Yes and no. Here are a few things to add in.
It is the two mic's difference in distance from the source that determines which frequencies add or null. As the difference increases from zero (zero being 'in phase') the effect begins in the high frequencies and extends lower. This can be pretty dramatic if the two are at similar volumes as within the first several inches it gets down into the midrange.
At some point out in a room the reflections tend to be as loud as the source and more random and you're playing more with the room's tone.
And as you have found, the mix of the second mic is essentially your wet/dry mix, whether it's the depth of the phase effect, or doing it's room-verb thing.
And yet another angle to play with would be to pull both mics back a bit where the cab's tones might be pleasing, but the mic phases ares still fairly close.
Happy hunting.
Wayne

 

[VesuviusJay]

It is the two mic's difference in distance from the source that determines which frequencies add or null

I have also heard phasing issues when using a stereo pair as you point the mics at different parts of the speaker itself even keeping them equidistant. Which is the use for the technique I described. This is one of the most interesting topics in this BBS.

 

[cello_pudding]

man, i love hr, but some of you guys really post pages and pages and pages of text.

i would like to say...

3 to 1 distance ratio rule. for every 1 away from the instrument mic 1 is, multiply by 3 = distance away from that mic.


does it really take 10 pages to say that?

 

[punkin]

I do this exactly quite often. Unlike some, I have found that the distant mic often sounds quite good. It could have to do with a number of things, room, mic, amp, cabinet etc.

I'll usually go with SM57 up close, I recently purchased an E609 but it hasn't grown on me yet. I'll then put up a LDC at about 5 feet away from the cabinet slightly higher up as it seems to me that down low, the bass response is a bit too punchy.

Play a few simple scales nice and slow then go back and look at the phase relationship of the the three mics. Move as needed until it looks AND SOUNDS GOOD.

 

[metalhead28]

man, i love hr, but some of you guys really post pages and pages and pages of text.
i would like to say...
3 to 1 distance ratio rule. for every 1 away from the instrument mic 1 is, multiply by 3 = distance away from that mic.

does it really take 10 pages to say that?

No, but if that was all that needed to be said, I'm sure your way would be very helpful!

 

[grn]

I think the original poster answered his own question, he said it only sounds good when he close mic's it at low volume... so do that. What these guys have said is very helpful... but in the end, it only matters that it sounds good.

I think they're forgetting the basics really. Get your amplifier OFF OF THE GROUND... put it in a wooden chair preferably and make sure it sounds good in the room. Then put your ear next to the amp while you're playing and get the sound you want ... you can't stand above it, beside it, or under it... you need to be right where the mic will be to see how it will sound. Then if you close mic it off axis (just point it towards the outer edge of the speaker cone) with an MXL990 or i5 or whatever you want and it should sound VERY close to how it sounded when you put your ear up to it. You'll only need to do a tiny bit of experimenting with mic placement if at all after that.

Phase shouldn't be an issue, you can set up more than one mic, but you really only NEED one. You won't damage the condensor (besides mxl990's aren't that expensive)... if you're that worried, put a pop screen in front of it, but they can usually take quite a pounding.

 

[mixsit]

man, i love hr, but some of you guys really post pages and pages and pages of text.

i would like to say...

3 to 1 distance ratio rule. for every 1 away from the instrument mic 1 is, multiply by 3 = distance away from that mic.


does it really take 10 pages to say that?

I'll tell you what, you tell why (or what) 3-1 does for this, and I'll come back with why I think it's irrelevant in this case. It'll be fun. Fair enough?
Wayne

 

[mixsit]

I have also heard phasing issues when using a stereo pair as you point the mics at different parts of the speaker itself even keeping them equidistant. Which is the use for the technique I described. This is one of the most interesting topics in this BBS.

Yes, and this is where the 3-1' thing get fuzzy -two mics at equal distances. I think the same thing applies when we get into stereo micing an acoustic. If two mics are placed spread out, say one at the body, one on the neck joint, they are both getting a bit of the others focus point, but on the whole, the guitar is generally in phase. Look at the ORTE mic technique.
(Hell, I off today; Our Lord Everest says '.. at low frequencies the signals ... are virtually phase coherent... with minimal phase differences becoming apparent only at higher frequencies, the comb filter effects are tolerable producing a pleasing air around the subject.' The New Stereo Soundbook

And the tool box becomes deep and wide.

 

[VesuviusJay]

Phase shouldn't be an issue, you can set up more than one mic, but you really only NEED one

I disagree. I haven't discovered or found a technique yet that compares to proper miking with a stereo pair. A single mic fails to compare with the depth of 2 mics. It is as if the track from a mono source is one dimensional sounding as compared to the pair, which when pulled off, produces a 3D guitar track.

 

[SouthSIDE Glen]

Yes, and this is where the 3-1' thing get fuzzy -two mics at equal distances. I think the same thing applies when we get into stereo micing an acoustic. If two mics are placed spread out, say one at the body, one on the neck joint, they are both getting a bit of the others focus point, but on the whole, the guitar is generally in phase.

I agree that both the definition and the application get fuzzy there, but one way to clean some of that fuzziness is to consider that the mics are not really micing the same source.

On a git cab, one might have a mic on the voice coil and another on the outer rim of the cone. These are miced seperately because, sonically speaking, they are two different sources. Looked at that way, on a 12" speaker, the two mics are going to be at least 4"-5" away from eah other while being only about 1" from each of their sources. Well within the the 3:1 rule. But the trick is, because of the small initial distance between the "sources", there is a very small "window" where when you move closer you are not micing the same source anyway, in which case the 3:1 rule becomes academic.

It's a similar story on an acoustic guitar. At close range - well within the nearfield of the guitar - the body and the neck are distinct and discrete sources. So the 3:1 rule still applies for near miking there as well. It's when you start approaching the edges of the instrument's nearfield that the "sources" start merging into a guitar and the 3:1 thing gets real murky.

G.

 

[VesuviusJay]

On a git cab, one might have a mic on the voice coil and another on the outer rim of the cone. These are miced seperately because, sonically speaking, they are two different sources. Looked at that way, on a 12" speaker, the two mics are going to be at least 4"-5" away from eah other while being only about 1" from each of their sources. Well within the the 3:1 rule. But the trick is, because of the small initial distance between the "sources", there is a very small "window" where when you move closer you are not micing the same source anyway, in which case the 3:1 rule becomes academic.

NICELY PUT!!!

 

[SouthSIDE Glen]

I disagree. I haven't discovered or found a technique yet that compares to proper miking with a stereo pair. A single mic fails to compare with the depth of 2 mics. It is as if the track from a mono source is one dimensional sounding as compared to the pair, which when pulled off, produces a 3D guitar track.

A stereo pair is a different animal than near/far miking.

Unless one has an excellent-sounding room, dampening the close miked signal with a little quality verb is in many instances probably better than adding a far mic, if that's what one is looking for.

The stereo pair can - with a good room - produce a dimensional soundfield if they are far enough from the source to get the delay and verb information from the rest of the room, essentially dual far mikes.

Again, the same caveat has to apply as with all conversations like this: It all depends upon the sound one is looking for and what kind of music and arrangement it's going into.

G.