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Cutaway acoustics
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Author:  mark m [ Sun Oct 05, 2008 9:54 pm ]
Post subject:  Cutaway acoustics
I have a very newbie question so bear with me. How much effect does a cutaway have on the acoustics of a guitar? Would it be less tonally balanced than say a guitar made the same size and not cutaway? I know there are some different bracing considerations for a cutaway and perhaps this counters for the loss of soundboard? Thanks!
Author:  Michael Jin [ Sun Oct 05, 2008 11:19 pm ]
Post subject:  Re: Cutaway acoustics
I think this is one of those difficult questions to answer because there's no way to really test this... Personally whenever I've played cutaway and non-cutaway versions of the same model, I've noticed no significant difference and any differences that I have noticed could easily be attributed to the fact that the two guitars a different instruments... Even if it's the same model, no two instruments are exactly the same... The one major difference of course, is playability on the higher frets. Personally I don't see a whole lot of reason NOT to make a cutaway other than the added difficulty in most instances, but then again that's just my personal opinion formed from my personal experience. I'm sure there will be others that do feel that the cutaway makes a much more significant difference in tone or other characteristics.
Author:  Michael Dale Payne [ Mon Oct 06, 2008 9:52 am ]
Post subject:  Re: Cutaway acoustics
If it were possible to build two exactly identical guitars except for the cutaway there would have to be some tonal difference due if nothing else than the change air chamber volume. That said how much would be hard to quantify. Intuition would tell me the cutaway would have a bit lower main air frequency, But the mass of the body would lighten a tad.

All in all the area of the top and back that is removed for a cutaway is not a particularly active area.
Author:  mark m [ Mon Oct 06, 2008 10:03 am ]
Post subject:  Re: Cutaway acoustics
I thought the upper bout delt more with the treble and the lower bout was more related to the bass. So if you took away area that produced the treble then the sound would be unbalanced. Is my logic faulty?
Author:  Michael Dale Payne [ Mon Oct 06, 2008 10:11 am ]
Post subject:  Re: Cutaway acoustics
Most all of the tone of a guitar produced buy the plates is in the lower bout, both trebel and bass. the onlything I see a cutaway doing is decreasing the the volume of the air chamber. This decrease in volume I would think lower the resonant freqancy a bit. but I really suspect by very very little.

Now the upper bouts will be much stiffer than the lower bout so the free resonants found ther would tend to be higher than the lower bout. but the vast majority of the sound generated by the plates are in the lower bout.
Author:  Pat Foster [ Mon Oct 06, 2008 12:16 pm ]
Post subject:  Re: Cutaway acoustics
MichaelP wrote:
........ the onlything I see a cutaway doing is decreasing the the volume of the air chamber. This decrease in volume I would think lower the resonant freqancy a bit......



Michael,

Did you mean here that the decrease in volume would raise the resonant frequency of the air chamber? That would be my belief. Little guitars, less bass, big guitars, more bass...

Pat
Author:  Alan Carruth [ Mon Oct 06, 2008 12:29 pm ]
Post subject:  Re: Cutaway acoustics
Pat's right; reducing the air volume raises the 'main air' pitch. Try blowing across the mouth of an empty bottle, then put in some water, and do it again: you'll get a higher pitched note.

One of my customers, who spends a lot of time in the studio, says that cutaways are eaiser to record. I suspect, but can't demonstrate, that the 'Q' values of the higher pitched 'air' resonant modes are lower with the cut, owing to the asymmetry. This would make the high end sound less 'peaky', and thus a little easier to record. Other than that, there doesn't seem to be a lot of difference so long as you keep the cut small.
Author:  Michael Dale Payne [ Mon Oct 06, 2008 12:43 pm ]
Post subject:  Re: Cutaway acoustics
dang it I did get it backward oops_sign
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