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Any of you ever use spruce for your backs? I think I have heard of this being done before and have been entertaining the idea of giving it a try. My only bad thoughts about the idea is belt buckles, nickel silver onyx bolo's and other such western wear. Good thoughts on the idea? I don't know. Hence my question especially to those of you who have done so, is it worth it? What tonal colours will such a box create, what will it take away?

One I feel you would have to brace so firmly to avoid being over active combined with the soft wood issue where the body gets the most abuse. To me it just seems impractical.

Spruce is fine.
I saw an all spruce Martin last year-sounded great !
Guitars with Cypress Backs last along time-spruce &Cypress are about the same hardness.
Also I've used Port Orford cedar-nice guitars.
I have an all Lutz Flamenco hanging in the shop that taps out nice !!
Can't wait to hear this one.

I leave softwood backs at least 2.7mm(.110) thick.

Mike

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Mike Collins

Have a look at Claude Boucher He make an all-Adirondack guitar. I'm afraid the video is in Quebecois French.

http://www.laguitare.com/2007/boucher/report_af_2.html

There was a recent post mentioning one of the famous classical builders who made some guitars with spruce or cedar backs. I believe that he veneered them with BRW or similar, so they had surface protection. By the way, these were widely referred to as "double top" long before the Nomex builders latched onto the same phrase for the sandwiched tops.

Interesting idea but I am wondering what the goal is - what are you looking to accomplish?

Hesh !!
I'm talking nylon strung gitars!!

Lithe in weight .-need for "Flamencos"
Less damping then heavy woods.
Small body-37mm max.- -sides 90mm to 95mm high!
650mm scale -you know the typical martin !!

Mc

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Mike Collins

Though I am Canadian my French sucks, but I found the video very interesting, I love to see different building ideas and fixtures.

Fred

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

I know of a fellow that built an "all spruce" harp guitar. click right herefor some pictures and information. If ever there was a demanding design, its one of these.

I am not sure of the bracing he used. However, I guess what you want to do is possible.

Mike

Hesh that is a great question and the answer is I don't know

I am hoping that someone here with experience can tell me if it's even worth it, what tonal qualities to expect, ups and downs, that sort of thing.

You see about 15 years ago I was building a Cherry Spanish guitar. I had the ribs all lined out and connected to the neck in my mold. While vacuuming the hose caught the edge of the mold on the work bench and it took a nose dive headstock first to the concrete floor and the neck ripped right through the ribs. I salvaged the neck and made a clean cut on the sides. These ribs have been hanging in my workshop as wall art and a reminder of how stupid one can be in one's own shop. Well I was looking at it the other day and thought I can make some funky experimental out of it. I've got some low grade spruce laying around and some time so I was just wondering if it's worth the effort.

Got it! Kind of like why does man climb a mountain.......

Ah. Low grade. I think grade is the key. The fellow who built the All Spruce guitar had a special billet that he thought was of exceptional grade. I do not understand why, but he kept it submerged in a bathtub all of the time. Maybe somone who understands this can explain.

Mike

Mike my friend maybe the billet talked too much and would not shut-up...... or it was ticking........

I have no french but enjoyed the Boucher guitar video too. I liked his quick and easy method of locating the bridge. If you look at the harp guitar link that Mike posted and follow it a bit it gives a good toot on rope binding.

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Steve Smith
"Music is what feelings sound like"

Right Hesh!

I would think a big downer with a spruce back would be dings and dents. Maybe you could coat it in thin, wicking CA to harden?

Hardening somehow seems to be the key.

That rope binding process was rather cool, huh?

Mike

I played an all spruce guitar at Epic Guitars in Carlsbad California. It was built by John S Kinnard. It was very nice. Light weight and very loud. It was pretty well balanced too. Go to his website, link below, and it is pictured there - the second one from the bottom.


http://www.johnkinnard.com/

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

... just to mention that Benedetto made an "all spruce body" archtop some years ago.

Best
Martin

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Martin G.
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www.best-eurospruce.com

Mike Collins wrote:
"Less damping then heavy woods."

Although people often talk about the inertia of a dense wood adding to 'damping', that's something of a mis-use. Technically, damping refers to the loss factor; how quickly the thing turns vibration energy into heat. A lot of the dense woods, such as Brazilian rosewood, have very low damping, as can be heard by the long 'ring' when you tap them. Most softwoods, with the exception of redwood and Med. cypress, have higher damping.

Part of the reason for using denser woods on the back has to do with the different job it's being called on to fulfill. All of the string energy goes through the top, and in order to produce sound the top has to move. Since there's not much energy in a plucked string you've got to keep the weight of the top down, and can accept a bit of loss from damping. The back acts, at least in part, as a reflector. Any energy the back gets has to come out of the top, which is much more effective at making noise. Most of the direct contribution of the back to sound output is in the low frequency range, and possibly in the 'attack' part of the sound.

As an example of a light back wood, look at mahogany. A rosewood back can weigh three times as much as the top, but a mahogany back might not be much heavier. Thus as you go from rosewood to mahogany, you tend to get more attack, and less sustain. The 'brightness' of mahogany might have something to do with that attack, and also with the higher damping factor of the wood. It's sometimes hard to sort out the various subjective differences and assign them to one or another physical cause.

An interesting softwood to try for a back would be redwood, which often has damping as low as that of the rosewoods, and good stifffness and surface hardness too. You can find really nice redwood at the lumber yard sometimes: I've gotten some that tested out to be a good match for the coveted 'LS' redwood. you could end up with a very 'Flamenco' sounding instrument.

The few spruce backed instruments I've seen were not wonderful....

Al,

I see you specified Mediterranean Cypress. Does the California stuff have higher damping? I've never used cypress, but I'm considering it. I've found mahogany to vary a lot with damping. Some pieces seem to ring very nicely. I find a lot of the non-rosewood or non-rosewood like "alternative" tonewoods to have very high damping.

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Randy Muth
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I'm a dummy when it comes to the actual tech./language .

But I do know that a spruce back can work-just like many other softwoods.
I use my ear (very important for me )& experience to make guitars .
I just sold an all Port Orford (top,back,and sides)"Flamenco" to a well know player and it was not a heavy set(compared to spruce)
The darn thing was as the buyer stated to me "just like Sabicas guitars sound"and this player could make it sound like him also!!
I think we as makers "artists" if you will, have to make gut feeling & experience decisions.
Tech. is not all knowing !
if it was we would all be making the same instruments -because science told us this is the only way!!

Gee Al; I stink at explaining myself!
I hope I did not offend you!!

You going to the GFA convention in June??
Mike

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Mike Collins

Mike Collins wrote:
"Tech. is not all knowing !"

Amen!

"...if it was we would all be making the same instruments -because science told us this is the only way!!"

Maybe we would, IF everybody could agree that there was only one good guitar design, and IF everybody could agree on which example of that design was the best one and IF we understood perfectly how it worked. The first two 'ifs' are NEVER gonna happen, thank goodness, and the third is extremely unlikely in my lifetime.

At best, I think, acoustic science in this business is of similar utility as, say, chemistry is to a painter, or engineering to a sculptor. A painter has to know what vehicles to avoid, and how certain pigments act in given circumstances, but if he's not a good artist he won't paint something that people want to hang on the wall, even if it will last a long time and keep it's colors fresh. The 'art' in the sonic part of this craft is in knowing what sound you want to make, and having some idea of where the balance point is that's going to get it. After that you can use the 'science' part to help fine tune things, and keep you out of trouble (maybe).

I'm not offended: 'science' was 'way over sold for a while there, and I can understand a reaction against it. I think both extremes are harmful. Certainly, as has been said: "No occiloscope can tell me what good sound is", but rejecting the benefits that a scientific approach can confer for that reason is a real shame.

"You going to the GFA convention in June??"

No: I'm going to be busy getting ready for the Montreal show.

I agree Al!
I use scientific approaches without even knowing it.
It's from reading articles by you and others .
All that info gets logged in this old brain and comes out while making guitars !
I record all specs. for my guitars and many repairs that come in !
resonance frequencies ,wood stiffness-etc..
Thanks for the understanding !!
And all the help you give the members here !
Good luck in Montreal !!

Mike

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Mike Collins