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I finished my first classical build about 9 months ago-east indian rosewood back and sides, cedar neck and top, rosewood headstock veneer, fretboard and bridge, ebony bindings, based on a Hernandez design. The top has seven strut fan bracing with two transverse bars between the end of the struts and the tail block. The neck is dovetailed, rather than spanish heel construction. The sound and tone and sustain are reasonably good-the bass is excellent-except that the treble becomes "thin" in the higher registers, from the 8th fret on, with a marked loss of sustain. There has been no significant change over the palying in period. I recognise that this is now part of the inherent acoustic characteristics of this guitar, but I would like to know the likely cause and what I can do to avoid this next time around. Anyone got any suggestions?

What strings are you using? Try some fluro-carbon trebles, Savarez Alliance or Savarez Corum, or maybe Pyramid Super Classic Carbons or Hannabach Goldins, they will usually produce a brighter treble. Every guitar responds differently to strings, it's worth experimenting with make and tension. Find the brand you like best then try different tensions of that brand.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Western red cedar top, correct? It's an interesting question, I don't have any answers, but, just curious, spruce bracing? and what is your top thickness?

Yes, plase tell us about the top thickness, lower bout width, bridge weight, and bracing characteristics.
If the tone is thin, I feel carbon might only make it worse.

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Build log

First of all, thanks to all of you for taking the time to respond- much appreciated.
Strings are normal tension D'Addarios,and are probably now long overdue for a change, tho' the guitar hasn't had much playing- too busy on the next one! I'm not familiar with the string brands you have mentioned, Colin, and haven't seen them on retail sale locally, so if you can recommend any internet suppliers I'd be grateful. Re the guitar specs: WRC top was thickness sanded to 3mm (.124") after installing rosette but before any further work, so is probably a hair less than that now. Strutting is spruce, fans 3.5 by X 7mm at 32mm centres, cross braces 7 X 17mm, with a pair of soundhole reinforcing struts 1.5 x 20mm, all dimensions before finish sanding. Overall length is 485mm, lower bout 363mm, waist 236mm and upper bout 274mm- a fairly standard Hernandez design. The only real departure was the addition of two transverse "closing" struts between the end of the fan struts and the tail end of the guitar; these were to the same finished dimensions as the fan struts. I didn't record the weight of the rosewood bridge, but it is to a very standard design.
Regards, Chris

Normally people avoid giving thickness advice and guesses since we try to spread the (correct) notion that it is the actual piece of wood that matters and not some standardized thickness ranges, however, in your case I might not be too off commenting. At an uniform thickness of 3mm minus a hair or two from clean-sanding, even with very light cedar, it is still probably too thick, and even more so for a small shape Spanish style guitar. Assuming your cedar is not of some extreme density, perhaps a 2.7-2.8mm center thickness, tapering to c. 2.3-2.4 at the edges, is more appropriate.

If the guitar is indeed overbuilt I would expect a thinner, bright tone out of it. Carbon trebles are brighter than nylon, and metallic - I wouldn't try them.

One more thing, how are your fan braces. 7 wide and 3.5 tall or the other way around. How much tapering at each end, and what profile.

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Build log

You might try sanding the top between the ends of the bridge wings and the wide part of the lower bout. This will sometimes help bring up the trebles.

One way to find out if you have an adequately thick top is to do a deflection test under string tension. You'll need a dial gauge for this. Clamp the guitar down face up on a table, using blocks under the edges and the heel to support the back off the table top. Set up a dial gauge so that it touches the top 2" or so in front of the bridge, between the bridge and the soundhole, and zero it. Now slack the strings off without moving anything, and see how much top top rises at that point. A deflection of no more than about .018"-.020" is probably OK, although we still have a long way to go in assembling that data base! There's much more on this sort of thing in David Hurd's 'Left Brain Lutherie', which you can get from him (ukulele@ukuleles.com) or, I believe, through Stewart-MacDonald.

Once again thanks to you all. Alan..the resanding is out, because I don't want to have to refinish the guitar, but I'll bear your suggestion in mind next time around, and try to be a bit more scientific about top thickness and graduation. The deflection test will have to wait too, because I don't have a suitable dial indicator, but again, it's something I'll bear in mind for the future. Alexandru...your suggestion re thickness and graduation is again something that I'll bear in mind for the future....I suspect that overbuild is possibly the root cause of the problem, and I doubt that I paid sufficient attention to this during construction. The fan struts are 3.5mm wide by 7mm high, finished to a knife edge, with the last 25mm scalloped down to about 1-1.5 mm.
For the time being, I'll experiment with better quality strings and see if that improves things.

Regards, Chris

I've started doing deflection testing using the depth gauge of the caliper. Then bought a dial indicator for both deflection testing and for a thickness gouge and I like the caliper better. You just need to eyeball-level it to the board unloaded and loaded and do the subtraction. It is very precise contrary to the first feeling you might get while reading this. A 0.1mm misalignment between wood and bottom of caliper just screams to the eye. The only (small) downside is you can't measure in the center, just at the end or side of board.

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Build log

Hi Chris

Treble response is The challenge in classical building, bass is easy.
I have not built any classical guitars but have had many discussions
with wise enthuisiasts on the classical build. The most practical help
without modification of your guitar is indeed going with higher tension
strings. This however is just that, a help not a solution. The mantra
is built in light light, depending on the stiffness of your top, 2.3mm
seems to be a more common thickness, even for cedar. Angling the
Harmonic bar {think Fleta}. Some ommit the bridge plate. Even the
closing bars are up for debate. Obviously structural integrity must be
maintained, but this is going in the direction of a more responsive
classical guitar. Just something to think about.

Best Wishes,
Paul

Just to clarify,that's 2.5mm at the edges.Also you could open the harmonic bar(tunnel) and extend the treble bracing thru the tunnel a bit.Peace,Paul.(Chris,part of my family lives in Tralee,maybe we can have a pint someday)

Sorry,clicked too soon.2.3mill.

Thanks guys, plenty of food for thought and future projects. This was my second guitar and first classical, and with both builds, I know I tended to err on the side of caution where thicknessing was concerned. My third effort was a OOO cutaway which, through a litany of errors ended up considerably thinner round the soundboard edges than I had ever intended! However it turned out not bad at all, and is currently alive and well in Boston, Mass. (With a name like Paul Murphy, I would have guessed there were Irish roots somewhere-I'm at the other end of the island from Tralee, but know it well-Kerry is a beautiful county. If you ever manage to make it up to the North, look me up and I'll stand you a pint of the black stuff!

Regards, Chris

"If you wish to build guitars, you must first learn patience"

I just strung up my first classical and it is as good in the treble as I could have hoped for.
All I can say is I built it light 2.3-2.5 mm Englemann (not very stiff) 7 fans 4.mm X 5mm
triangleish profile. Longer tapers of around 35 mm down to 0.5 mm both ends. 3mm x .3mm closers. I think the transverse braces were around 7mm X 14mm.
Before the bridge went on I could depress the centre of the plate visibily with my thumb. I was convinced it was too light and it may well be.... but the bridge stiffened it up amazingly and I am delighted with the separation volume and top notes. There will be no HT strings on that guitar! Of course its all so subjective

Good Luck

What size lower bout and did you thin the edges around the lower bout, tapering down from the bridge area?

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Waddy

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Sound Clips of most of my guitars

Chris;
to get a good sustain & clear loud notes(ESPECIALLY ABOVE THE 7TH FRET) I add a 5mm thick X 80mm x70mm spruce under the f.board from the 12th fret (neck block)to the # 1 BRACE.
This mass added under the f.board helps alot with sustain & clear notes up high !
Works for me !
Give it a try .

Mike

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Mike Collins

Mike,

Interesting, So do you omit the upper transverse graft for this or do you sort of mesh that in as well? And is this cross grain spruce or directional?