Official Luthiers Forum!

Hey all,

Where do you guys draw the line between basic structural mechanical compliance -- the Macro level design of the top and bracing stiffness.... and Voicing.. which I think of as more subtle changes made to adjust the sound somehow or another.

How much "voicing" do you guys do after you get a guitar together and play?

Tinkering around with my Esteban retop project some more.... I have been playing it as-built
for about ~2 months now.... and it has opened up nicely.

This build sounded nice with Medium strings, but pretty average with Light strings.
With mediums -- it had a pretty substantial bass, but the treble didn't have the sort of ring I wanted.
With a 3/4" tall tapered X -- you wouldn't expect a strong bass..... so the Archive pointed me towards the bridge.

The bridge was pretty substantial -- a "Bought" unit, so I took a bit of weight off of the back end where the bridge pins go thru.
I reduced the height of the back end of the bridge about 1/16" or so.

I was surprised with how much the material removed off of the bridge really opened up the treble.
Overall it seemed to give it more sparkle and definitely more volume.
At the same time, it seemed to lessen the bass substantially.

Since my X is pretty tall at 3/4" at the cap, I started to scallop the lower X legs a little from the bridge back.
This seemed to open up even more volume, a little better tone, as well as restore a little bit of the bass.... so I am going to go slow on this... play another couple weeks to let it settle down... then see what happens to the sound.... maybe go in and whittle a little more. I still have enough brace there so that it is not going to go too thin too fast.

Anyway, I guess I was surprised how much a "small" change to the bridge weight made a large change to the sound.
I am also quite happy that this "Science project" of mine is working out.

Thanks

John

John wrote:
"Anyway, I guess I was surprised how much a "small" change to the bridge weight made a large change to the sound."

I'm not. The bridge is the first thing the string 'sees', and even a small change in impedance there can have quite an effect on the timbre.

The best stuff I've seen on compliance and voicing is in David Hurd's book: "Left Brain Lutherie". It's self-published, and I don't know off hand if any of the 'usual suppliers' carry it, but you can get it directly from him, I beleive. If you can't find him through a search on his name, try 'kawika', as that is/was the name of his ukulele brand.

you can also pick his book up at amazon.

http://www.amazon.com/s/ref=nb_ss_gw?ur ... ie&x=0&y=0

_________________
sweat the small stuff.

Well, I can post an update here.....

Basically, doing this shaving really brought out the treble and the treble tone in a good way, but I lost the bass... My G chord now sounds "Wooshy" and I don't like it.

It is mixed results, and I think it points out an early assumption of mine....

My assumption was that finger braces and tone bars were present mostly for crack prevention and for getting the top resonance into the correct region... and that the X should be the main structural member... Consequently, my X was too tall and the Tone bars and finger braces were *very* light and were spaced off of the main X quite a bit. It turns out that you can in fact build like this... and it will work. With mediums, I got a strong driving bass, not so crisp trebles, and a not really interesting tone.

Shaving the bridge and the light scallop ended up giving *Way* more treble and midrange volume.... but the bass..... not so good as above.

My hypothesis is the large very lightly braced lower bout lead to the main air resonance and main top resonance ending up very low... but the stiff centered X is messing things up otherwise. So... shaving things loosened up the middle a little -- and let the treble and mids shine out a little better... but it got too loose for the Bass

Since this is a beater, I am leaning towards pulling the back and fixing the top bracing with the goal of the top bracing working more like a "System".... Shaving the X back down to 1/2-5/8" tall at the cap, putting in a little more substantial tone bars and finger bars that are tightly butted into the X....
At least, that is what I am currently thinking.

Does this sound like a plausible hypothesis.... and the right track of action?

Thanks

I always think of the top and bracing as a system that works best when all of the elements are balanced in some sense. You can for example, get the resonant pitches up by putting heavy braces on a light top, or making a thick top with light braces, but either one IN THE EXTREME will not give a good sound. Bt the same token, a heavy X brace with a few little sticks for tone bars and finger braces is not really a system, and won't work as well as a more balanced setup. As usual, this gets us into sticky question, like 'where's the middle ground' and 'how do you know whan you've got it balanced'?

In many respects, 'standard practice' defines the 'middle ground', at least, if you look mostly at the better sort of instruments. The middle covers a lot of territory, if only because tastes vary so much. The variability of wood adds some scope to that as well.

There are innumerable ways of telling when you've got it right, and we each have our favorite. I use 'free' plate tuning; looking at Chladni patterns on the top and back before I assemble the box. It's hard to justify in any rigorous way, but it sure is easy to get at things! Hurd's deflection testing gets a lot of the same information, I think, after the box is together. It's easier to understand why it works, but harder to get in and make changes. You can get much of the same information by tapping and listening, and feeling the top as you push with your thumb, but it's harder to record that sort of information, and most of us don't remember that stuff as well as we'd like (at least, not at my age).

Anyone got an orphan back set they want to get rid of? Don't really care what wood... as it will be replacing plywood.

I will post pics of this bracing scheme for the world to see once I get it back apart.

Thanks

John