What does a too thin top sound like?

Construction and repair of Classical Guitar and related instruments

What does a too thin top sound like?

Postby Craig Bumgarner » Tue May 03, 2011 8:47 pm

What does a top which is too thin sound like, both in tap tones and when strung up and played. I ask in that I'm in process of thinning down a top on a completed guitar. The top was too thick to start with and the sound was tight and muted. I can hear the tap tones lowering in pitch and the response is getting stronger as I thin, but how do I know when I am going too far? What will this sound like? What is the effect on the strung up guitar, that is what does a top that is too thin play like. I have strung the guitar back up and tried it several times during the process and the tone and response are definitely getting better. How do I know when to quit? Or does one only learn this the hard way?

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Re: What does a too thin top sound like?

Postby Waddy Thomson » Tue May 03, 2011 9:14 pm

It's hard to know until you have gone too far. I go for a strong clear sound that I like, in a low register, and I try not to overwork it. You can do that.
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Re: What does a too thin top sound like?

Postby dng » Tue May 03, 2011 9:36 pm

like a banjo..?

:lol:

just kidding...
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Re: What does a too thin top sound like?

Postby Steve Ganz » Wed May 04, 2011 4:40 am

The hard way.
There are too many variables to give you a formula. The primary reason is that you are the biggest variable. Enjoy that!
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Re: What does a too thin top sound like?

Postby Alexandru Marian » Wed May 04, 2011 1:32 pm

The hard way. Don't forget to use your common sense. In any case, do not jump to conclusions too fast. Need to string it up with new strings and let it settle for several few days after each sanding session. Listen to it played by someone else too.
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Re: What does a too thin top sound like?

Postby Marcus Dominelli » Wed May 04, 2011 2:33 pm

I agreen with the other posts. Most luthiers I know (including myself) underbuilt, or overbuilt atleast one guitar. You pretty much have to go to these extremes to learn the limits. The more guitars you make, the better you get at optimizing.
My advice is to stop at a point where you are happy, or very close to happy with the sound. If you decide to "go that little bit extra" without the experience, you might go beyond safe point. Good luck.

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Re: What does a too thin top sound like?

Postby Craig Bumgarner » Mon May 16, 2011 4:52 pm

Well, lesson #1 in learning the hard way about voicing tops: There is a trade off between volume, frequency response and clarity.

I thinned the aforementioned top down in a few places, mostly around the edges just up from the bridge. As expected, the tap tones loosened up and the bass became more pronounced. When I OMMMM in vicinity of the sound hole, I find the body resonance has dropped from B to G. The increased bass response is an overall a plus, but it is maybe a little tubby sounding. The volume certainly increased, but when driven hard, chords have become somewhat flabby sounding, w/ less clarity. Is seems that though the top is now more responsive, it is also a bit too loose, if you will, and when energized hard by multiple strings the overall effect feels like the top is bit out of control.

The main lesson for me is that playing drives the top and if you play it hard, you get a different response than playing light (duhh.....) and that making the guitar more responsive when played light does not necessarily result in coresponding spectacular performance when driven hard.

Just an observation.......

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Re: What does a too thin top sound like?

Postby Steve Ganz » Mon May 16, 2011 5:18 pm

Craig.
Keep your mind and ears open during the entire process.
Your description makes sense to me.
Is the guitar finished?
That can settle things just a bit.
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Re: What does a too thin top sound like?

Postby Craig Bumgarner » Mon May 16, 2011 6:03 pm

Roger on staying open, good advise. One element not yet explored is how the guitar will now behave in a performance environment. i find that it is hard to predict when playing a guitar alone in my shop. I'll find out as soon as I get the top refinished.

Speaking of which..... Finished? All but the top at the moment. This is a guitar that I built and fully finished in the winter and after playing for three months decided to take a little off the top. The results I just posted are for the unfinished top (only). I started French polishing the top (for the second time) this morning. Yeah, we'll see what that adds to the mix.

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Re: What does a too thin top sound like?

Postby Jeremy Hickerson » Tue May 17, 2011 10:13 pm

In my experience I can hear the change in the treble strings more easily when thinning or reducing braces, etc. For instance, the G string is a tough one to keep from sounding tubby as the top stiffness is reduced. I would play single notes on the treble strings (open and fretted) and listen for the change as I thin.
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Re: What does a too thin top sound like?

Postby kiwigeo » Wed May 18, 2011 12:28 am

The focus of the thread so far has been on thinning the top. I would also look at the bracing. Could any benefit be gained from taking some meat off braces?.....bearing in mind that alot of guitars (including many of mine) are over braced.
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Re: What does a too thin top sound like?

Postby Craig Bumgarner » Wed May 18, 2011 3:31 pm

kiwigeo wrote:.... I would also look at the bracing. Could any benefit be gained from taking some meat off braces?.....bearing in mind that alot of guitars (including many of mine) are over braced.


I must admit this is a steel string Selmer style guitar with a very small oval hole, too small to get my hand in, so brace reduction on the finished guitar is not possible, at least by any means I can think of other than removal of the back, something I wasn't really prepared to do.

BUT..... I think you are quite right. To answer one of my original questions, an overly thin top sounds tubby and chaotic. I'm on the edge of that with the guitar in question. I think now, or maybe 0.2mm ago, what I needed was, just as you say, some meat off the two braces near the bridge. (Selmer style, if you are not familiar, usually use three to five ladder braces with only a couple if any longitudinal braces. This particular guitar has four ladder braces).

Eventually, I hope to get to a point where I can tune the top plate before full closure of the body, but I'm not there yet. The other possibility is to concentrate on Selmers with large D shaped sound holes. These are big enough to move the whole shop inside :D

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Re: What does a too thin top sound like?

Postby Jeremy Hickerson » Wed May 18, 2011 9:44 pm

I have had some luck in cases where I removed too much (either from top or from braces) in adding a thin, taller "sister" brace next to the back brace that is visible through the sound hole. I glue the brace to the back and to the side of the original brace. I use hide glue so this is reversible. In both cases this improved the treble response of the guitar; one was a steel string, the other a classical.
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Re: What does a too thin top sound like?

Postby harryschmidt001 » Fri Jul 22, 2011 2:18 pm

Hi Craig,
I just finished my first guitar build and have been searching for answers to this question too; worried that my top is too thick.
Came across this interesting research at http://www.speech.kth.se/music/acviguit4
Have a look at chapter 6 The Function, Tone, and Tonal Quality of the Guitar, page 23 section 6.7 CONSTRUCTION AND ACOUSTICAL PROPERTIES.
Page 31 shows their conclusion:
The experiments and calculations presented have shown that the bridge has the largest influence
on resonant frequencies and vibration sensitivity levels. The thickness of the top plate seems to
be the second most important, especially along the edges, and the width of the fastening is less
important than the thickness.

Any folks have thoughts/ideas on bridge design (size, thickness, shape, etc) and affect on sound?
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Re: What does a too thin top sound like?

Postby GeoffB » Fri Jul 22, 2011 4:33 pm

Hi Harry, welcome to the forum. Could I invite you to introduce yourself here?

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