Microphone placement.....?

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Russ Gannicott
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Microphone placement.....?

Postby Russ Gannicott » Fri Jan 09, 2009 12:04 am

OK, this is one for MikeS and any other technique/equipment junkies out there. I hate to admit defeat...but I'm stumped - what is the best way to mic up a 4x10 cab in the studio? Said cab is being drven at a high level by Ash's 15watt Tiny Terror and despite trying various microphones, all the results sound rather gutless and fizzy - totaly the opposite to what you hear. Any thoughts...? Remember that this is a valve amp being diven hard to achieve the desired sound, so turning it down won't help!!
Thanks in anticipation
Russ

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Mike Stranks
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Postby Mike Stranks » Sat Jan 10, 2009 10:52 am

Thanks Russ for the compliment of thinking I may be able to help!

Hmmm… could be all sorts of things so forgive me if I cover things that you’ve already explored.

First of all I’m assuming that you’re completely happy with the sound of the cab in the room – and in all parts of the room. If so, that rules out two things:
• Problems with the room acoustics
• Problems with the amp/speaker combination
However, just a couple of points on both of those. If the sound in the room is OK – including quite close to the cab - then we can discount room artefacts or any electronic funnies. You obviously want it loud to get the sound. If it sounds OK then it’s probably not a situation of the amp clipping because it’s being driven too hard. I know clipping and overdrive is very subjective with guitars and valve amps, but it could be a factor.

So what about mic placement? How close to the cab are you? Are you trying to capture the sound from all four speakers? If so, it could be that the mic is picking up the room sound which you’re not aware of when you listen to the cab. Also, if you are trying to capture the sound from all four speakers with one or more mics then phase (or more correctively, polarity) could be an issue. If the speakers are out of phase then that will make the sound thinner in a way that isn’t always detected by ear. In this approach, irrespective of phase, the sound may be thinner anyway. My technique is to go in fairly close – no more than a foot from the cab and often closer – and concentrate on one speaker. Point at the centre of the cone for a fuller sound and nearer the edge for something with a bit less bottom end. Of course there’s no ‘right’ way to do this – experimenting with placing the mic in several places let’s you judge. However, you know what you’re about so I guess you’ve already done this.

Next to consider is the mic itself. I note that you’ve already tried several. The mic of choice for cabs is the good old Shure SM57, but some people like to use a combination of one of these and a Large Diaphragm Condenser. I’d favour a dynamic, and as well as the Shure would consider a Sennheiser 421 or even a Beyer 201 – although the latter can be a bit too ‘clinical’ for some tastes. I’m guessing though that you’ve already addressed this aspect.

Which only leaves the recording side of things… Is there any possibility that you’re clipping the signal at any point in the chain? If it’s loud – as you say it is (understandably) you could be clipping the mic itself, the mic input stage of your preamp or mixer, or the recording device itself. Clip/overload lights should be warning you of this – with the exception of the mic – but sometimes transients can clip without lighting up anything. Incidentally, I’ve also known the input stage of recorders to clip when according to the meters it appears that you’ve still got headroom.

I presume you’re recording digitally and that you’ve got sufficient headroom and bit depth. For music I record digitally (uncompressed of course) at 44.1 KHz and 24-bit (this isn’t the place to explain this rationale!), with peaks notionally at minus18db. Even then transients can almost hit zero, but the risk of digital clipping is minimised.

Just some thoughts Russ. I know that you’re very experienced and that you’ve probably thought of all of these things. If none of this or your own further experimentation works then I suggest you try the ‘Sound on Sound’ forums. There’s loads of very experienced professionals go on there who might have some further insights. Hope you get it sorted soon!

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Russ Gannicott
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Postby Russ Gannicott » Sat Jan 10, 2009 7:08 pm

Thanks Mike, I knew I could rely on you confirm my own thoughts and come up with some good suggestions.
I checked things like speaker phasing and mic polarity with multiple mic placings, but still no good. The issue 'sounded' like a spl problem with the mics overloading - rather like you would get if for example you tried close micing a kick drum with a SM58. This got me thinking....I wouldn't want to put a bass guitar or kick drum through my PA's hf horns, I'd use a crossover. Why not apply the same idea to cabinet micing? I set up three mics; a C1000, SM57 and D112 at a range from 6 to 24 inches from the cabinet and then eq'd out the unwanted frequencies from each mic. The result is superb - exactly like the original and if I'd wanted I could have recorded onto more than one track for even greater flexibility. So, problem solved....thanks again for your thoughts!
Cheers,
Russ

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Mike Stranks
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Postby Mike Stranks » Sat Jan 10, 2009 7:24 pm

Excellent!

I was still mulling this over this afternonn whilst driving my daughter back to uni in Nottingham and was thinking about EQ as another possible fix-it! Glad you've got there with a mic combination and some judicious EQ-ing.

Mike

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Roger
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Postby Roger » Sat Jan 10, 2009 9:13 pm

Russ/Mike,

The following might be of interest:

http://www.soundonsound.com/sos/jul06/a ... ackson.htm

All the best,

Roger

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Russ Gannicott
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Joined: Thu Apr 26, 2007 8:28 pm

Postby Russ Gannicott » Sat Jan 10, 2009 9:44 pm

Thanks Roger, great article!
Yes Mike, the 'reverse engineering' of the sound really did the trick. I suppose if you think about it there is sound logic to applying crossover theory to mic placement, mic choice and eq-ing. I just never thought about using a kick drum mic on guitar cab before!
Thanks again for your help.
Russ

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Mike Stranks
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Joined: Sat Nov 03, 2007 8:47 pm
Location: Cirencester, UK

Postby Mike Stranks » Sun Jan 11, 2009 4:36 pm

Absolutely!

If it sounds right, it is right!

I remember a few years ago watching some jazz fusion from the Proms. I was aghast at first seeing an SM58 being used on a jazz-guitar - but it sounded great.

We can too easily become slaves to gear and what we "should" do. The standard approaches are good starting points, but we engineers should be just as creative in our use of resources as our musician brethren!


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