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  #1  
Old 03-29-2010, 07:53 PM
Cue Zephyr Cue Zephyr is offline
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Default Particular note 'thunk'

Hey everyone,

This probably has been discussed before, but since I don't know how to express it correctly and thus being unable to search effectively, I thought I'd ask it here for a quick answer.
My guitar sounds awesome (atleast that's what I think!), but some notes just sound weird, and one in particular. It's the G note in the first two octaves of the guitar. Hitting it gives me a thunk sound, as if it were rejected by the soundboard.

What is this phenomenon? Does it have a specific name? What causes it? Is there a guitar that does not have this?

I'm sure someone can tell me, so many smart guys on this forum!

CZ
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Old 03-29-2010, 08:39 PM
Bryan T Bryan T is offline
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G is probably the resonant frequency of the box.
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Old 03-30-2010, 07:44 AM
Cue Zephyr Cue Zephyr is offline
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Wouldn't that do the opposite? Like, make the box resonate more?
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Old 03-30-2010, 07:46 AM
PWoolson PWoolson is offline
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Quote:
Originally Posted by Cue Zephyr View Post
Wouldn't that do the opposite? Like, make the box resonate more?
Unless the resonant frequency is juuuuuuuusssssttttt off of G. Then it can kill the note. Not much can be done except to retune the top (shave the braces slightly).
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Old 03-30-2010, 08:50 AM
jmcphail jmcphail is offline
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Is it common for there to be particular notes that do this on guitars?
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Old 03-30-2010, 08:52 AM
Bryan T Bryan T is offline
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Quote:
Originally Posted by jmcphail View Post
Is it common for there to be particular notes that do this on guitars?
Yep, though some are more pronounced than others.
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Old 03-30-2010, 09:08 AM
Fran Guidry Fran Guidry is offline
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When a particular note finds a strong resonance the note explodes and dies, expending all its energy in a "thump" instead of a drawn out attack-decay-sustain-release pattern that we're used to. This is easy to see if you record the instrument and examine the waveform in a digital audio editor. The "dull" note that sounds muted is actually the loudest one in the track.

One trick is to play the note much more gently instead of the intuitive approach of playing it harder.

Fran
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Old 03-30-2010, 09:45 AM
Cue Zephyr Cue Zephyr is offline
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That was a great reply.
I never realised it worked that way, neither did I realise that it was actually the loudest note.
Thank you.
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Old 03-30-2010, 09:50 AM
willsing willsing is offline
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Quote:
Originally Posted by Cue Zephyr View Post
Wouldn't that do the opposite? Like, make the box resonate more?
I am not sure, but it sounds like phase cancellation. When the frequencies are the same, they cancel each other out. That's why stereo mics have to be carefully placed so they don't pick up the exact same frequencies, resulting in poor sound quality. Very interesting what Mr. Woolson pointed out. That explains the "f's" on the 5th string on two Taylors I have had. I just figured I can live with it since I have learned to appreciate the beauty of the other 99% of the notes. And thus far, it has not been a show stopper for any of the songs I have played. It only becomes an issue when I go into note testing mode, which is not part of a flowing, musical whole anyhow.

Hope you get it worked out though.

Will
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Old 03-30-2010, 09:59 AM
Bryan T Bryan T is offline
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Quote:
Originally Posted by willsing View Post
That explains the "f's" on the 5th string on two Taylors I have had.
That part of the A string is problematic for a lot of guitars. I played around it for a long time. Interestingly, my Lowden sounds wonderful on those notes and it has really changed the voicings that I choose to play.

I've had some archtop guitars that would go into howling feedback if you even thought about playing on the A string between the seventh and twelfth frets.
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Old 03-30-2010, 11:11 AM
Pat Foster Pat Foster is offline
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The resonant frequency of the top may be close to that of the box. If that's the case, you have the box and top resonant frequencies sort of conspiring to work together at the frequency that's giving you the "wolf note." If it's a new guitar, as it ages, the top may drop its resonant frequency enough to smooth out the peaky response it currently has. Also, it's more likely to happen on a responsive guitar.

Pat
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Old 03-30-2010, 01:16 PM
Huckleberry Huckleberry is offline
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It happens on all guitars but is more noticeable on responsive guitars.

If it's a dead note rather than a wolf note, I have a theory that it's caused largely by the resonant frequency of the neck, not the body.

I find guitars with carbon fibre neck inserts to be much more consistent and exhibit no dull notes. Perhaps the much stiffer carbon raises that resonant frequency out of harm's reach.

Usually you can play around it - treat it as a feature of the guitar, if it's not too severe.

To test my theory, try clamping a heavy capo to the headstock, to increase the neck's mass. Does the problem go away?
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Old 03-30-2010, 01:34 PM
Bryan T Bryan T is offline
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Quote:
Originally Posted by Huckleberry View Post
If it's a dead note rather than a wolf note, I have a theory that it's caused largely by the resonant frequency of the neck, not the body.

I find guitars with carbon fibre neck inserts to be much more consistent and exhibit no dull notes. Perhaps the much stiffer carbon raises that resonant frequency out of harm's reach.
That could be. It seems consistent with what I see with my Lowden, which as five-piece neck that seems to be very stiff.
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Old 03-30-2010, 08:30 PM
Broadus Broadus is offline
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The F# (4th fret on the D string) and the G on the D to a lesser extent are the culprits on both my Martin and Eastman OM's. When I first noticed it, I was traumatized. Had to do some internet searches and came across the resonance description. I recognize now that it seems to be the nature of the beast.

Bill
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Old 03-30-2010, 09:57 PM
stringjunky stringjunky is offline
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Quote:
Originally Posted by Huckleberry View Post
It happens on all guitars but is more noticeable on responsive guitars.

If it's a dead note rather than a wolf note, I have a theory that it's caused largely by the resonant frequency of the neck, not the body.

I find guitars with carbon fibre neck inserts to be much more consistent and exhibit no dull notes. Perhaps the much stiffer carbon raises that resonant frequency out of harm's reach.

Usually you can play around it - treat it as a feature of the guitar, if it's not too severe.

To test my theory, try clamping a heavy capo to the headstock, to increase the neck's mass. Does the problem go away?
I found this interesting entry on an electric bass forum that seems to support your thought:

Many stringed instruments will have "dead" notes where the vibration of the neck & body are out of phase with the vibration of the string and dampen it, reducing volume and sustain. Likewise many instruments will have "live" notes where the vibration of the string is in phase with the body and neck and so the note is augmented. The classic example is that a large number of Fender-style basses have a dead spot at (or around) the seventh fret on the G string. My '74 4001 has a slight dead spot on the 7th fret of the D string, and my '74 4000 has the Fenderesque dead spot.
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