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A storm's coming & hopefully we won't loose power

Here are new plots.

These were done using David's technique, tail resting on my leg, hand on neck holding down strings, mic about 24" (0.6m) away .

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

OK. Those plots look a lot more normal, with the peaks where I'd expect to see them. I don't think you're getting any particularly negative interaction between the top and the back. A main top peak at ~190Hz is nicely placed for a 000 and that in itself should not be causing a loss of responsiveness. Testing its monopole mobility will give you a measure of that.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

As Trevor said, the 'main top' freq (192) is fine. The 'main back' (258) is on the high side, although there are a lot of schools of thought on that. The 'main air' (104) is also good for an OM. 383 is probably one of the dipoles, also normal range. The little 287 in the top plot is probably from the back (the 291).

With those numbers and a lack of treble, it's hard to recommend any brace shaving for the top (generally, that would make it louder but even less treble-balanced). Possibly you could shave the back braces to get the 'main back' down to 220 or so for more overall power and tone color, but it probably won't affect treble much. I wouldn't try that first, though.

For more treble, Alan C has recommended selectively thinning the periphery of the lower bout, to the left and right of the bridge. I've tried that a few times and it seems to work. Don't thin the periphery around the tail, though -- that makes more bass. IIRC, for more treble he recommends thinning from the waist down to about the 4 and 8 o'clock positions. I think the idea is to loosen up the cross dipole so it's more active. About 0.020" of thinning has worked best for me (and much more than that has had the opposite effect on treble). One way to keep track is to make some 'calibrated scratches' around the periphery, then sand till they are gone. I use a 'coupon cutter' which has a tiny razor blade that sticks out about 0.010" -- easy enough to make. Test the method on scrap spruce first, so you can measure it before and after with a caliper.

It's also possible the top was a reject part for being too far off-quarter -- that would kill treble. Easy to check if you have your top scraps.

Given the normal resonant frequencies, your original thought on a lighter bridge sounds like the best plan to me -- that will definitely help treble. I would go as light as possible (walnut?) but keep the wings reasonably thick and stiff. Mario and Trevor can get their bridges down to ~15g, I think. Your ebony bridge may be more than 30g. And cheap plastic bridge pins save a few grams. I'd replace the bridge first, since periphery thinning can't be undone, and it doesn't have the big effect you're looking for.

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David Malicky

Our power has finally came back on, we sure are spoiled. Three days without electricity felt like an eternity - even when I was able to go to a friend's who had power.

I just got Alan's DVD which I'm hoping will give me a foundation in Chladni patterns etc. I'm also thinking Trevor's books will be a good investment, once I stop blowing all my extra money on wood.

In the meantime & I have a lot of your ideas to investigate.

Thanks again.

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

could someone explain why slotting the braces into the sides has a bad affect on the sound?

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We are all in the gutter but some of us are looking at guitars.

Joe,

That only applies to the lower x's, the finger braces, and the tone bars.
Upper transverse and upper x ends should be notched into the sides or somehow supported.

The reason some people like to thin the lower braces to zero at the ends is to loosen the edge of the top for a bassier response.

klooker,

$250 on the Gore/Gilet books is a better investment for you than wood. Contains the info you need to get the tone out of your tone wood.

I'm sure you're right and it's also less than taking a course or attending a seminar but when you're face to face with a special piece of rosewood or Ziricote or even Mahogany, all logic & reasoning goes out the window.

Kevin Looker

I will buy the books, just after this last wood purchase...

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Kevin: I have a good liberary of luthier books and I lately have come to the conclusion that the Gore/Gilet books are the most informative of the lot. Not always light reading but certainly very very well covered. Buy it...............if you are going to continue on with the building..............don't think you will be disappointed.
Tom

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A person who has never made a mistake has never made anything!!!

Wish I'd thought of that one...

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Dave and Trevor seem to have pretty well covered the water front. Get Trevor's books: you won't regret it.

Hi Kevin,
This is a great thread that you have started here , and you have built twice the guitars that I have so you probably know twice as much as me about them. And a lot of very knowledgeable builders have put in their thoughts.


If I go back to your first post and look at the pictures , is it possible that your saddle is a bit low ? and wouldn't a 64th or three higher saddle solve this problem?
When I put my first saddle in I could not get over what a big difference it made . I was raising and lowering my first trial saddle by placing veneer strips under it trying to solve a buzzing string problem, and the shape of the saddle problem compared to the fretboard . I was all over the place with it , learning.
It was a shock to hear just what a difference the saddle height made. its huge.
I left it at what looks like a very high .1929 of an inch or 4.9 mm ,that's at the middle of the saddle of a 9.5 mm bridge .
I can bring it back down a little if my top starts to move , If my bridge last that long.

Rob.

I haven't played with the saddle height because I want to keep the action as low as I can.

I agree that the saddle is a little low & it's worth a try but this also has me thinking about how much the top raises when I tension the strings.

When the strings are off & I put a straight edge across the frets, it projects over the bridge by about 1/64" which is on the low side but acceptable per Compiano. But then I have to thin my saddle to get the action down. This made me think of Waddy's comment:



Since the top raises so much under tension, maybe it is too loose around the bridge. I need to get out the dial indicators & get some real data for this.

One more thing about the saddle, when I fit a new saddle with no slop, the volume or power increased but the overall tone stayed the same, just louder.

I also ordered Trevor's books this morning.

Thanks again for all the comments.
Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

I have a dozen or so documents on guitar acoustics broken down to such technical details as specific gravity and modulus of elasticity, and their effect on acoustics. They add up to 13MB, and I'm busy enough working on my shop that I likely won't get around to putting them onto one of my servers for public access overly soon. If anyone would like to host them for sharing around here I would be more than happy to upload them.

Quick follow up.

I ordered Trevor's books on Thursday morning. They arrived Monday.

Awesome service & awesome books.

I've just started reading the design guide but I've looked through both.

IMO, these are definitely worth the price, as good or better than any college texts I had while studying mechanical engineering.

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Where do you order the Gore/ Gillette Book? Directly from Trevor here on the forum and how much ?

Google Trevor Gore Guitars and you'll get there!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Hi Kevin

How did you get the photo of the frequency plot from Audacity?

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

I did a screen capture (Alt-PrintScreen) then pasted it into Photoshop.

I then went back & manually typed in the frequency values so it would be easier to read.

I'm sure you could paste it into a free image manipulation program or even Microsoft Paint, I just happen to have an old copy of Photoshop & it's easiest for me.

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.