Official Luthiers Forum!

So here's the short of it.

My first guitar had the best sound of all the guitars I've made (OM). I've always thought the bass strings could be a little more piano like (it's kinda dull) but that flaw not withstanding....I really like it.

But I can't reproduce it.....

My thinking is I should 'dissect' my first guitar to take measurements and weights etc.

But it's my first guitar.....

Any thoughts?

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

Get a Hacklinger guage.

Chris, my first thought is even if you could measure every part of your favorite guitar perfectly, the measurements might not translate into as good sound as the next guitar because of the variation in materials and the building/environmental variables that inevitably happen. Don't mess up your best guitar imo. Keep better records going forward and each time review/compare notes before starting the next build. Your guitars will get better.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

You gotts to be kidding...

no two peoples the same...
identical twins are not "identical"...
even consecutive serial numbers of the Marin assembly line sound different.

May look alike and even sound alike...
but still ...all are different.

You can't rebuild the past...
but you can build another and another and another ...
even mass produce and guess what...

Right!...Different.


Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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A few thoughts-
How many guitars are you comparing?
Same strings?
How old ? (Does the first guitar just sound better because it's older and been played more?)
All made from the same woods, same bracing (pattern and sizes?)
Same bridge? (Bridge is by far the heaviest (and often, stoutest) brace on the top...)
Same string distance off the soundboard?
I don't think you need to dis-assemble the guitar to make your measurements.
If you are not sure that you followed a bracing pattern closely, you can take pics/tracings with a light inside the guitar.
You could think about making a Hacklinger gauge (diy instructions are around on the web or in the GAL magazine?) to measure plate thicknesses.
Chladni patterns on the top may give you some data.
Deflection testing of the top (Dave Stewart does this on his archtops & there was info on this in a report of a mandolin-building course - Siminoff???- in the GAL mag) by weighting the bridge area on the finished guitar.
Tap tones using computer software (like Audacity?) and a mic....

You are not alone! I think this is a recurrent 'nightmare' for builders- making a great guitar 'by accident' and not having enough data to replicate it.
I've (very) recently started keeping a lot better records of my builds for this reason- not that I am anywhere near making a great guitar, though....

Cheers
John

EDIT- Others typed faster than me! BTW, builders do seem to develop a characteristic 'sound', so some things can be replicated, though the definition of 'identical' is certainly the question....

If you're trying to duplicate the sound, then you have to measure sound. Duplicating the thickness of the top or the mass of the bridge (if you knew it) won't necessarily get you the same sound. If it did, there'd be a lot more great instruments around: all Taylor would have to do its get it right once, and set up the CNCs for that.

It's not too hard to measure the sound of the assembled guitar in some useful ways. I like the sort of 'sound snapshot' you get from an 'impulse response'. I hang the guitar up with the strings damped, using a loop of string under the E string tuner buttons, and tap on the bridge saddle with a free-swinging hard plastic or hard wood bead about 3/4" in diameter. Record the sound from out in front and put it through an FFT program on your computer. This tells you how much energy the guitar can put out at different frequencies. Guitars with similar spectra tend to sound similar, and after a while you get to where you can 'read' the chart and get an idea of how the guitar sounds. The problem then is 'merely' to make nother one that has the same spectrum, more or less, as the one you like.

If you have a signal generator or can coax your computer and an amp to do that duty you can look at the Chladni patterns of the assembled box. Again, it's simple to do, and might help you duplicate the tone. I once made a reasonably close 'tonal copy' of an old Martin OM from the impulse spectrum and mode data, so it's possible. It's also quite possible I got _very_ lucky on that one.

My feeling is that the earlier on in the process you can make the tonal adjustments the easier it is. That's one reason I like Chladni tuning. It's not perfect: I've never managed to make a truly 'matched pair' that were indistinguishable from each other. But it can help you get close.

Since you don't have that data on the one you've got you're sort of stuck. Again, I'd try the Chladni data on the assembled box, and make a WAG about how to thickness and brace a new set of wood to get it to do that. Keep really good records of things like resonant pitches, mass, deflections, anything you can think of that might have a bearing. When you get it together, see how close you got, and make adjustments on the next one to try to get it closer.

In the end, the most important tool in the shop for getting consistent results is the piece of paper you keep the records on. Some people can remember this stuff, or claim they can. I need to write it down. I've got a file folder on each guitar I've made over the past fifteen or twenty years, and some scattered data from before that. Mark Blanchard, the 'King of Consistency', has a thick notebook with all of his in it.

Okay....I'll leave it together. What's been said here makes sense to me. Time to start recording things.

Thanks Folks!

_________________
There is no difference between the man that thinks he can....and the man that thinks he cannot.

I guess I would ask....

What is the better? Is it louder? Is it more enveloping? Is it more Projecting? Is it the sound Balance? Is the intonation better? Is the setup better? Or.. Is it just older and you played the stuffing out of it?

Then... What are you comparing it against? For example -- if you built 3 different models from 3 different sets of plans.... vs if you made 3 more according to the same plans...

One big thing... The guitar is a system... If you spend all your time on the braced top... you are ignoring the entire rest of the instrument -- Bridge, back, finish, etc... As such, you may need to think about your "Mental Model" for each one -- how did your mental model change as you built each one... What were your experiments? What can you pin down as potentially being responsible for those changes? Are there any experiments you can try to make adjustments to the ones that weren't fully successful on the instruments you have already made?

For example -- My Oakie Ditson 11 came out initially much quieter and much thumpier than it's cherry brother... My main suspicion was that the bridge/bridge plate combo was too heavy and *way* too stiff (I had built it that way as an experiment)... I had to do quite a bit of carving on that bridge to loosen it up.... I then decided to experiment with carving the Back bracing to bring out some more of the voice... It worked, and the voice really came out... Hopefully I learned something that I can apply into the builds I am currently working on...

Last thing I will leave you with is:
The statistical definition of "Average" -- For there to be an "Average" ... There has to be a "Better" and a "Worse".... If you have more than 1 instrument.... there will be a "Best" and a "Worst"... No getting around it.... Nothing we can do about it... It's just the nature of the universe.

Thanks

John

Did you keep notes on plates thickness, bracing dimensions etc.? If not a large violin thickness caliper (you can build your own for the cost of a dial gauge) can help give you your plates thicknesses through the soundhole, you can measure the rest.
In any case the variance between woods of the same species and different builds of the same model are often greatly exagerated around here. If you use the same dimensions and woods on 2 guitars of the same build, chances are you'll end up with 2 instruments sounding almost the same. One may seem better than the other, and probably is, but your results wil be constant. A D-28 sounds like a D-28 and a whatever model Taylor sounds like a whatever model Taylor. It's a good idea to try to replicate what has been successful, and dimensions and wood choices are the obvious (and right) start. Then, IMHO there's no other way to refine the process than to test one change at a time, perhaps on a test mule if you're disapointed.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

You can find dial gauges on sale for $15-20; you'd probably have to build a few different 'frames' if you were working through the soundhole. The 'quick 'n dirty' version I made doesn't have the 'trigger' you often see, but works OK- you just have to lift up the 'probe' between measurements via the 'knob' on the top of the gauge. A minute of 'practice' will show you to 'rock' the gauge to get the minimum reading- works well.