Guitar tops: anything else than spruce or cedar?

Discussions relating to the classical guitar which don't fit elsewhere.
Carlos
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Guitar tops: anything else than spruce or cedar?

Post by Carlos » Wed Dec 06, 2017 1:18 pm

Hi there,

We have some variety of woods to use for the back and sides, but all guitar´s tops I see are made of spruce or cedar. Are there any other variety of wood being used? And would you mind sharing experience/knowledge on the resulting sound?

Thanks for any hint!

Cheers,

Carlos.

(ps: I am aware some built guitars with innovative materials like carbon fiber, but I am asking mainly about wood)

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HNLim
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Re: Guitar tops: anything else than spruce or cedar?

Post by HNLim » Wed Dec 06, 2017 1:41 pm


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Justfun
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Re: Guitar tops: anything else than spruce or cedar?

Post by Justfun » Wed Dec 06, 2017 2:29 pm

Pine top
Red wood
And maple top
Richard Reynoso, Cypress \ Spruce 2016
Lozano Spruce 2001
Inofuentes 1997

Laudiesdad69
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Re: Guitar tops: anything else than spruce or cedar?

Post by Laudiesdad69 » Wed Dec 06, 2017 2:56 pm

Koa

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Peter Frary
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Re: Guitar tops: anything else than spruce or cedar?

Post by Peter Frary » Wed Dec 06, 2017 4:32 pm

The most common non- spruce/cedar sound board wood I've seen is redwood. However, the character seems very similar to cedar. Love the tone. I'm not a fan of hardwoods on guitar tops but some steel strings players like maple and koa tops for stage guitars with pickups.
I play a Cordoba Mini so I look taller on stage!

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Michael.N.
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Re: Guitar tops: anything else than spruce or cedar?

Post by Michael.N. » Wed Dec 06, 2017 5:13 pm

Many things have been tried but there's obviously a reason why soundboards (not just guitars) are virtually always made of a lightweight wood. As Mr. Carruth keeps reminding us - nylon strings have a limited amount of energy that they can put into the soundboard, may as well use a wood that responds readily to it. That means cedar, spruce types, perhaps a lightweight fir or a lightweight pine. Even cypress might be a candidate although I can't say that I've ever seen a guitar soundboard made from it, some Italian harpsichords were.
Historicalguitars.

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bert
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Re: Guitar tops: anything else than spruce or cedar?

Post by bert » Wed Dec 06, 2017 5:48 pm

Not sure, but I believe I once tried Bernabe M30 with a sequoia top

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Muggins Simoon
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Re: Guitar tops: anything else than spruce or cedar?

Post by Muggins Simoon » Wed Dec 06, 2017 6:24 pm

Sequoia (redwood) makes a great top.
2011 Mathieu Trepanier Sitka/Koa
2000 Otto Vowinkel Concert Spruce/Brazilian
1998 Christopher Dean Spruce/Indian
1995 Richard Schneider Sequoia/Brazilian
1979 Dauphin Model 40 (Japan-signed label) Cedar/Indian

Alan Carruth
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Re: Guitar tops: anything else than spruce or cedar?

Post by Alan Carruth » Wed Dec 06, 2017 7:39 pm

Some basic numbers are good place to start answering this sort of question: you can measure the relevant material properties of various woods and see how close they come to the 'standard'; European spruce. As Michael says, with only limited horsepower in the strings we need to keep the top light if we're going to get any power or treble response. Reasonably low 'damping' should help too: we don't want the string energy being dissipated by friction or other losses in the wood. Strength is far less of a consideration than is often assumed; any wooden top of more or less traditional construction that is stiff enough will in all likelihood be stronger than it needs to be. Also, apparently cross grain stiffness is not nearly as important as it's often thought to be; it seems to have some acoustic effects, but is not as useful structurally. So, we're probably most interested in how stiff a piece will be along the grain, and how much it will weigh when it's 'stiff enough' for a guitar top.

If you're talking about pieces of wood of the same thickness the material property that determines how stiff they are is the 'Young's Modulus', abbreviated as 'E'. The E stands for 'extension': Young's modulus is a measure of how much force it takes to stretch (or compress) a piece of material of a certain size by a given amount. When you bend a piece of wood you're stretching the fibers on the outside of the bend and compressing the ones on the inside, so the Young's modulus comes into play; for a given thickness of piece the higher the E value, the harder it is to bend.

If you think about it, it's the fibers on the top and bottom surface of the piece that do most of the stretching and compressing. This means that, all else equal, a thicker, or deeper, piece will be stiffer. We all know that, of course, but it's well to keep it in mind. For one thing, the piece gets disproportionally stiffer as you make it deeper; all else equal the stiffness will go as the cube of the thickness of a top, or the depth of a brace. A low density piece of wood that has a low E value can still end up making a light top if adding thickness brings the stiffness up without making it too heavy.

What this says, then, is that we're most interested in the relationship between Young's modulus for extension along the grain and density. These are relatively easy things to measure. If you look at these for a lot of different kinds of wood you start to see some interesting things.

One is that hardwoods often don't genrally have E values that are much higher than those of softwoods, but the hardwoods are usually denser, and often much denser. This means that hardwood tops, when worked to the correct stiffness for a guitar top tend to be much heavier. This is not universally true, of course. For one thing, hardwoods are more variable in their structure and properties than softwoods, and some of them are notably low in density with reasonably high E values. Balsa is technically a hardwood, for example, and has been made into very light instrument soundboards. Of course, it has drawbacks, particularly low surface hardness. Still, in general, if you're looking at common hardwoods you'd be hard pressed to find one that would make a soundboard as light as most softwoods. To put a number on it, most rosewood samples I've tested have had long-grain E values on the high side of the range I've seen in spruce, but the rosewoods are at least twice as dense, and some, such as Morado and African Blackwood, as much as four times.

Compared with hardwoods, softwoods are all structurally quite similar, which means that they tend to vary less in terms of the properties we're looking at. Granted, individual pieces of softwood can vary a lot in density, but it turns out that the relationship between Young's modulus and density doesn't vary much across softwood species. What that means is that if you want to make a light weight guitar top you can use just about any species of softwood, so long as the density is reasonably low.

To put some numbers on that:
The softwood samples I've measured range in density from about 300 kg/cubic meter to around 550 k/m^3. The E values at the low end of the density scale cluster around 6000 MegaPascals, while the densest samples are close to 19,000MPa. When I chart them out, and draw a straight line between those values, I find that something like 60% of all the samples measured fall within 10% plus or minus of that line.

Different species of soft woods tend to have different densities. Western Red Cedar tends to be the least dense of the 'usual suspects' I've tested, with Engelmann being next up in the scale. That's followed by European spruce, Sitka spruce, Redwood, and Red spruce, in order. Those are the only ones I have large enough numbers of samples for to be reasonably confident of the averages. At the same time, I'll note that there's a LOT of variation within any species. The densest samples of softwood in my data are a couple of pieces of European spruce, I have Red spruce samples that have density as low as WRC, and so on. The moral here is that the only way to know the properties of a piece of wood is to measure it.

Along with the usual suspects, I have tested quite a number of 'alternative' softwoods. Often I have seen only one or a few samples of any of those, but, for the most part, they follow the same rule relating E and density. Of these I, and may students, have used at least a half dozen for guitars, and all have worked out about as expected given the measured properties. These include several spruce species, such as White spruce, Lutz spruce, and so on, as well as White pine, Western hemlock, and Douglas fir.

All of this assumes that a maker can, and will, vary the thickness of the top to obtain the 'correct' stiffness, whatever that is. Given the way stiffness and thickness are related, a thick top of low density can weigh less than a thinner one of high density wood, as has been said. It's fairly easy to solve the equations that tell you how much a given sample of top wood would weight when worked to that stiffness. It turns out that, in general, the lowest density tops will be about 25% lighter than the highest density ones. This is a useful difference: 'sandwich' tops tend to be about 40% lighter than ones of 'standard' construction, and that accounts for the added power.

Again, cross grain stiffness does not seem to be as important as long grain in the long run. Also, cross grain stiffness is far more variable, being chiefly predicted by the angle of the annual ring lines to the face. Since this can vary a lot even within a single piece, and the loss of cross stiffness for a small deviation from 'perfect' quarter can be large it's something that has to be dealt with top by top.

It is hard to say what effect damping has on tone. Part of the reason for this is that damping is less straightforward to measure than density and E. For one thing, it varies with frequency, and may do so differently for different species. Wright's modeling study included damping as a variable, and found no significant effect from changing the damping by a factor of three.

Steel string guitar groups on line in particular abound with threads trying to describe the tonal differences between different spruce species. Often this devolves into a 'wine tasting' discussion, with subtle subjective perceptions being given the weight of gospel. As somebody who has tried to make 'matched pairs' of guitars that sound the same (without success as yet), I can say that even matching everything one can think of to within a few percent still results in instruments that sound different, and the scale of the differences is pretty much in the 'wine tasting' range.

Finally; it's my belief that guitars are physical objects that obey physical laws. If it can't be measured it's not there. This doesn't mean we know everything that we should measure, or that the measurements will be easy. What it does mean is that I'm not going to spend time talking about leprechauns; the world is complicated enough without them.

johnd
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Re: Guitar tops: anything else than spruce or cedar?

Post by johnd » Wed Dec 06, 2017 7:45 pm

Allan,
I am so glad you are on this earth!!!!! Thank you.

ben etow
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Re: Guitar tops: anything else than spruce or cedar?

Post by ben etow » Wed Dec 06, 2017 8:36 pm

bert wrote:
Wed Dec 06, 2017 5:48 pm
Not sure, but I believe I once tried Bernabe M30 with a sequoia top
I tried one with a sequoia top, but not all are. Very nice.

I also tried a guitar with a redwood top (lattice braced), more than very nice...

ben etow
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Re: Guitar tops: anything else than spruce or cedar?

Post by ben etow » Wed Dec 06, 2017 8:38 pm

Muggins Simoon wrote:
Wed Dec 06, 2017 6:24 pm
Sequoia (redwood) makes a great top.
Oooops, didn't kno it was the same :?

Carlos
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Re: Guitar tops: anything else than spruce or cedar?

Post by Carlos » Thu Dec 07, 2017 9:48 am

Thanks to all of you for sharing your experience - and particular to you dear Allan for your magistral explanations! (btw you should write a book to share your findings...)

I would really love to be able to test a sequoia with a guitar top ...and even more I think if I could find a guitar with cypres top as if I understand well this could also work out, right?

Dear Muggins Simoon: could you describe your experience with sequoia? And also, I see in your signature you have a Sitka/Koa guitar. Is Sitka for the top? How does it sound? Thank youin advance!

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guitarseller345645
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Re: Guitar tops: anything else than spruce or cedar?

Post by guitarseller345645 » Thu Dec 07, 2017 10:30 am

From the bay:

Carvalho Classical Guitar, 5Koa
Sandwiched Solid koa top, back and sides
Item ID: GR50030 Model No: 5 KOA Made in Portugal

3 layers of Koa wood Top 1.5mm, middle 0.5mm, inside 0.5mm. Great grain top with great stability and sound
Kremona Fiesta FC

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Michael.N.
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Re: Guitar tops: anything else than spruce or cedar?

Post by Michael.N. » Thu Dec 07, 2017 11:22 am

Carlos wrote:
Thu Dec 07, 2017 9:48 am
Thanks to all of you for sharing your experience - and particular to you dear Allan for your magistral explanations! (btw you should write a book to share your findings...)

I would really love to be able to test a sequoia with a guitar top ...and even more I think if I could find a guitar with cypres top as if I understand well this could also work out, right?

Dear Muggins Simoon: could you describe your experience with sequoia? And also, I see in your signature you have a Sitka/Koa guitar. Is Sitka for the top? How does it sound? Thank youin advance!
I have a bit of experience with cypress but only when used for back/sides. I've used it for classical guitars rather than flamenco guitars. Generally speaking it's towards the top end of spruce in terms of density which probably means it can be made to work as soundboard. Then again you might have to ask yourself the question as to why you would use cypress over commonly available spruce? What are you hoping to gain? Personally I don't see any advantage other than the hope that it will do something special, which is almost certainly deluded. Unless you like the appearance of it as a soundboard which is a completely different reason to any tonal considerations. You'll get the lovely aroma of cypress I'll grant you that. Is it worth the risk of making a guitar with a cypress soundboard? If you are not paying for it or paying very little then perhaps it is. If you are a maker willing to experiment and you aren't under time/money constraints then go right ahead. Personally I doubt that it will be any better than a piece of spruce with the same density numbers (it may not be any worse though). I could be wrong of course, I've not done that particular experiment but I think I have enough experience that tells me that there's no nirvana.
Historicalguitars.

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