spruce from pine

[Viking]

Originally Posted by Alan Carruth

I think the higher damping of the oak may have contributed to a reduction in the high frequency output of that guitar, as compared with the lower damped rosewood.

I wonder though, and not to cast any kind of accusation at you at all, but how much do our preconceived ideas about the species of wood play into what we hear?

Some blind testing on this issue would be helpful.

[printer2]

Originally Posted by Viking

I wonder though, and not to cast any kind of accusation at you at all, but how much do our preconceived ideas about the species of wood play into what we hear?

Some blind testing on this issue would be helpful.

I would think that anyone that went through the trouble of making identical builds with just the wood change may have put their preconceived opinions aside, otherwise they would not have bothered.

[printer2]

I just had a thought (boy I think of this stuff too much). If Rosewood makes for good backs, fretboards, bridges, and if they make guitar tops out of Mahogany, Walnut, Koa, could they make a top out of Rosewood? Might not be as loud as a spruce top but maybe it will make up the loss in volume with being a very resonant top. Mind you thinning it down enough probably means your bracing might play a bigger role in the sound of the guitar.

[Alan Carruth]

printer2:
It's darn near impossible to put preconceived notions aside, which is why 'double blind' testing is so extensively used.

In that 'pair' test, I had both crude objective measurements of the response, and listening tests, and the results seems to corroborate each other. With only one test, of course, there's not a lot you can say for sure.

" If Rosewood makes for good backs, fretboards, bridges, and if they make guitar tops out of Mahogany, Walnut, Koa, could they make a top out of Rosewood? Might not be as loud as a spruce top but maybe it will make up the loss in volume with being a very resonant top."

Right on both counts: what little sound it had would probably be really nice. I'll note that mahogany, walnut and koa are used as tops on steel string guitars far more often than Classicals: I can't think of a single classical guitar with any of those on the top. Usually, when they do use hardwood on tops, it'son smaller bodies, or 'acoustic-electric' instruments. It's easier to make a loud small guitar than a loud big one, so the penalty is less. with acoustic-electrics it can be an advantage to have a top that doesn't put out as much sound, since it is less prone to feedback.

Structurally, the top of the guitar has to be stiff enough to resist the static bridge torque over the long term. Most of this comes from the bending stiffness along the grain, which is pretty much proportional to the Young's modulus of the wood along the grain and cube of the thickness. With a specific gravity of around 1 (about the same as water) Brazilian rosewood tends to be two or three times as dense as softwoods. In softwoods the Young's modulus along the grain scales pretty nicely with density, and some of the more dense samples of spruce will have a Young's modulus only about 25% lower than that of BRW, for half the density. The lighter softwoods that we tend to use for Classical tops will have Young's modulus values about half that; roughly 1/3 the value for BRW, but they're also about 1/3 the density. If you do the math you'll see that the lower density wood will make a much lighter top at a given stiffness.

You don't necessarily give up anything on damping either by using a softwood. Western red cedar has very low damping, and Redwood can have damping as low as that of BRW. Cedar and redwood tops are not generally noted as being 'bright', which is what we tend to expect from low damping: just goes to show that things don't always work the way you expect them to.

[spuerspeedo]

Originally Posted by printer2

Here's the body, wood from an old barn. Actually built by one of our very own posters.



I can't find the build thread but I am pretty sure this one has a pine top.

http://www.youtube.com/watch?feature...v=e0ht46wafN0#!

Hi printer2 and viking i was just wondering how you all add photos on here?

[spuerspeedo]

Originally Posted by Alan Carruth

printer2:
It's darn near impossible to put preconceived notions aside, which is why 'double blind' testing is so extensively used.

In that 'pair' test, I had both crude objective measurements of the response, and listening tests, and the results seems to corroborate each other. With only one test, of course, there's not a lot you can say for sure.

" If Rosewood makes for good backs, fretboards, bridges, and if they make guitar tops out of Mahogany, Walnut, Koa, could they make a top out of Rosewood? Might not be as loud as a spruce top but maybe it will make up the loss in volume with being a very resonant top."

Right on both counts: what little sound it had would probably be really nice. I'll note that mahogany, walnut and koa are used as tops on steel string guitars far more often than Classicals: I can't think of a single classical guitar with any of those on the top. Usually, when they do use hardwood on tops, it'son smaller bodies, or 'acoustic-electric' instruments. It's easier to make a loud small guitar than a loud big one, so the penalty is less. with acoustic-electrics it can be an advantage to have a top that doesn't put out as much sound, since it is less prone to feedback.

Structurally, the top of the guitar has to be stiff enough to resist the static bridge torque over the long term. Most of this comes from the bending stiffness along the grain, which is pretty much proportional to the Young's modulus of the wood along the grain and cube of the thickness. With a specific gravity of around 1 (about the same as water) Brazilian rosewood tends to be two or three times as dense as softwoods. In softwoods the Young's modulus along the grain scales pretty nicely with density, and some of the more dense samples of spruce will have a Young's modulus only about 25% lower than that of BRW, for half the density. The lighter softwoods that we tend to use for Classical tops will have Young's modulus values about half that; roughly 1/3 the value for BRW, but they're also about 1/3 the density. If you do the math you'll see that the lower density wood will make a much lighter top at a given stiffness.

You don't necessarily give up anything on damping either by using a softwood. Western red cedar has very low damping, and Redwood can have damping as low as that of BRW. Cedar and redwood tops are not generally noted as being 'bright', which is what we tend to expect from low damping: just goes to show that things don't always work the way you expect them to.

Wow! there is so much to learn about the wood and making Guitars, where do you learn that sort of informtion? Like BRW and damping? I feel a bit stupid asking but if i dont ask im not going to get anywhere in the Guitar game.. I really get a lot out of what you have to say printer2 and all you guys!!!!

[printer2]

Originally Posted by spuerspeedo

Hi printer2 and viking i was just wondering how you all add photos on here?

When you do a reply to thread, you click on the little button that looks like a mountain and sun(?), and paste a link into it from a picture hosting site like photobucket.

[printer2]

Originally Posted by Alan Carruth

printer2:
It's darn near impossible to put preconceived notions aside, which is why 'double blind' testing is so extensively used.

In that 'pair' test, I had both crude objective measurements of the response, and listening tests, and the results seems to corroborate each other. With only one test, of course, there's not a lot you can say for sure.

" If Rosewood makes for good backs, fretboards, bridges, and if they make guitar tops out of Mahogany, Walnut, Koa, could they make a top out of Rosewood? Might not be as loud as a spruce top but maybe it will make up the loss in volume with being a very resonant top."

Right on both counts: what little sound it had would probably be really nice. I'll note that mahogany, walnut and koa are used as tops on steel string guitars far more often than Classicals: I can't think of a single classical guitar with any of those on the top. Usually, when they do use hardwood on tops, it'son smaller bodies, or 'acoustic-electric' instruments. It's easier to make a loud small guitar than a loud big one, so the penalty is less. with acoustic-electrics it can be an advantage to have a top that doesn't put out as much sound, since it is less prone to feedback.

Structurally, the top of the guitar has to be stiff enough to resist the static bridge torque over the long term. Most of this comes from the bending stiffness along the grain, which is pretty much proportional to the Young's modulus of the wood along the grain and cube of the thickness. With a specific gravity of around 1 (about the same as water) Brazilian rosewood tends to be two or three times as dense as softwoods. In softwoods the Young's modulus along the grain scales pretty nicely with density, and some of the more dense samples of spruce will have a Young's modulus only about 25% lower than that of BRW, for half the density. The lighter softwoods that we tend to use for Classical tops will have Young's modulus values about half that; roughly 1/3 the value for BRW, but they're also about 1/3 the density. If you do the math you'll see that the lower density wood will make a much lighter top at a given stiffness.

You don't necessarily give up anything on damping either by using a softwood. Western red cedar has very low damping, and Redwood can have damping as low as that of BRW. Cedar and redwood tops are not generally noted as being 'bright', which is what we tend to expect from low damping: just goes to show that things don't always work the way you expect them to.

But dampening and Q can be frequency dependent. I see the woods as a tuned filter network. One wood may have the same dampening or resonance as another but they may have their resonance in different bands.

And thanks for the good information.

[Viking]

Originally Posted by spuerspeedo

Wow! there is so much to learn about the wood and making Guitars, where do you learn that sort of informtion? Like BRW and damping? I feel a bit stupid asking but if i dont ask im not going to get anywhere in the Guitar game.. I really get a lot out of what you have to say printer2 and all you guys!!!!

Start reading and playing with wood! Also, if you have someone near where you live who build stringed instruments, go hang out with them and ask them questions. I've read Cumpiano, Somogyi, and lots of information on the internet. Lots of knowledgable people here on this forum, and the "Official Luthiers Forum".

[spuerspeedo]

[spuerspeedo]

[IMG][/IMG]

[spuerspeedo]

[IMG][/IMG]

[spuerspeedo]

[IMG][/IMG]

[spuerspeedo]

[IMG][/IMG]

[spuerspeedo]

[IMG][/IMG]