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micing acoustic guitar for live purposes

#1 User is offline   mattchance 

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Posted 28 November 2007 - 12:18 PM

So yesterday I was doing a live session for a band and was having a nightmare with the acoustic guitars...One was an electro-acoustic (no problem as DI was on hand) and the other was a straight up acoustic. It just seems I could not get enough volume from the acoustic before it fed back. I used various microphones (Shure Beta57, AKG C451 and an AT404) but the problem persisted. Is there a proximity effect issue when micing up acoustic guitars and is this why they feedback hideously when you're trying to get a good gain structure? any tips and help much appreciated

:)
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#2 User is offline   klemay 

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Posted 28 November 2007 - 12:46 PM

Ok, first of all, mic choice, go with a capacitor mic, they're much better for picking up acoustic instruments.
Secondly is positioning of the mic, which should be roughly just over a foot away from the instrument, you will have to experiment on where the mic is pointing to get the best sound, most of the time ive found that if you point the mic directly into the sound hole , you get a very boomy sounding acoustic guitar which you have to spend forever trying to EQ and will very often feedback, so try off setting the mic slightly. You may also want to try adding a second mic and having a stereo pair on the guitar, this is quite a common thing to do. Again experiment with the positioning of the mics to get the best pick up. Also a touch of reverb doesnt go a miss either.

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#3 User is offline   Bobbsy 

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Posted 28 November 2007 - 01:12 PM

Cardioid condensor mics are my preference for miking an acoustic guitar and a C451 is pretty much my favourite. Frankly, if you couldn't get sufficient gain before feedback using this you may need to consider some other aspects of your setup.

One thing, as mentioned by klemay, is the positioning of the mic. I've always found the best position, both for tone and for GBF, is over the fingerboard, about halfway between the sound hole and the end of the body. Pointing directly at the sound hole can give a very boomy, very prone to feedback sound. For recording purposes I always mike an acoustic guitar in stereo but I'm less convinced about the for sound reinforcement, given that each time you double the number of mics you reduce your gbf by 3dB. Reverb is also likely to cause more, not less, feedback.

Using a guitar pickup (as opposed to a mic) is always an option when high levels are needed, but obviously it DOES alter the overall sound.

Otherwise, speaker (both FOH and monitor) positions need to be considered...as does the overall SPL you're working at. There comes a time when, just like Scotty, "ye cannae change the laws of physics, Cap'n".

Bob
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#4 User is offline   mervaka 

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Posted 28 November 2007 - 01:37 PM

yeah, the first thing I watch is the foldback level.

#5 User is offline   mattchance 

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Posted 28 November 2007 - 02:05 PM

thanks for that, all mics used were about 5" away from the fretboard and the mics were aimed about 6" up the fret board away from the sound hole. I have a feeling the cause of feedback may have been due to proximity to the actual PA, it's only a small PA for acoustic sets so the players are situated closer than desired. as far as foldback goes I was barely getting enough useable signal to send to the monitors so that wasnt really an issue
thanks for input

:)
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#6 User is offline   Dan Appleby 

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Posted 28 November 2007 - 02:15 PM

If you can get hold of one, Shure KSM 137's sound beautiful on acoustic guitar (as they do on most acoustic instruments), and are better than some other condensors out there for feedback.

Bobbsy hit it on the head with mic placement... Don't point it directly the hole, but put it off-axis while pointing it towards it - the air that comes out of the sound hole, while it's not alot, is enough to give you booooomie-ness on a sesitve condensor. As always with these things, try a few different positions and see what works out best for you.

If you are really struggling with feedback, you should be able to use a 57/beta 57 without too much problem, and still get an acceptable sound.

The other thing to bear in mind is stage level... if you have a loud band, your going still going to struggle to make the acoustic cut through the stage noise, even if the mic is fairly near the guitar!

My 2p. Hope it helps!

#7 User is offline   gyro_gearloose 

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Posted 30 November 2007 - 01:52 PM

It all depends on whether the guitarist moves around, but you could try two mics in a crossed pair arrangement placed where Bobbsy has suggested. One should point to the area that the strings are plucked and be EQ'd to give a bright sound with no low frequencies. The other mic should point at the body where the ends of the strings are attached and be EQ'd to give a warmer sound with no high frequencies. You can then pan the two mics a little to the left for the low frequencies, and right for the high frequencies.

I realise that this probably won't help with your level or feedback issues, but it does sound good.

Have a look at this guide for lots of useful info.

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