Hardwood soundboards

[fishstick_kitty]

Originally Posted by RussMason

...Hardwood tops tend to be brighter sounding than spruce, which is a soft wood....

I used to think that too...until I owned a Santa Cruz 1929 00...it's really warm sounding...much warmer than most Sitka/Mahogany guitars I have owned. It all has to do with the builder sometimes.

[Garthman]

You can make a guitar soundboard out of any wood you want - or any other rigid material for that matter. The purpose of the soundboard is to provide a large area to cause more air molecules to vibrate within the sound-box of the instrument. Obviously the board has to transmit the vibration of the string via the saddle and bridge - but most rigid, solid materials besides wood (plastics, metals) do this pretty well.

The main reason that spruce and cedar are used for soundboards is (a) historic (because they are easily worked with the tools that existed back then) and (b) because they possess the best thickness to strength ratio amongst wood species.

[fishstick_kitty]

Originally Posted by Garthman

You can make a guitar soundboard out of any wood you want - or any other rigid material for that matter. The purpose of the soundboard is to provide a large area to cause more air molecules to vibrate within the sound-box of the instrument. Obviously the board has to transmit the vibration of the string via the saddle and bridge - but most rigid, solid materials besides wood (plastics, metals) do this pretty well.

The main reason that spruce and cedar are used for soundboards is (a) historic (because they are easily worked with the tools that existed back then) and (b) because they possess the best thickness to strength ratio amongst wood species.

I think there's a little more to it than history...every wood has different sound characteristics. I don't see too many guitars out there with a plastic top...and I'm sure it has been tried. A plastic top would probably sound different than spruce or cedar

[slinco]

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[prsplayer12]

Originally Posted by slinco

It has always surprised me that mahogany is considered a "tropical hardwood". I've worked with it over the years (old boats, furniture), and believe me, it's not that hard. It must be one of the softest of the hard woods, which means it's probably not that far up the hardness scale from the hardest of the soft woods. I could be wrong...maybe an expert can weigh-in on this.

Its about a 2250-2300 on the Janka and is one of the softer hardwoods.. Brazilian Ebony is the hardest at about 3700.

Mahogany is right around where the curve from softwoods to hardwoods occurs.

http://tinytimbers.com/pdf/chart_janka.pdf

[MBE]

An interesting point made by the OP is that we don't see mixing of hardwood tonewoods that we know sound good.

A Koa top, rosewood (or coco, or ziricote, or blackwood) back/side guitar would be absolutely stunning visually in my opinion.

A walnut top, rosewood back/sides would also be beautiful.

If Koa and walnut tops work on all-Koa and all all-walnut guitars, why couldn't they work with other back/sides?

[John Arnold]

It has always surprised me that mahogany is considered a "tropical hardwood".

"Hardwood" and "softwood" are botanical descriptions, not an indication of the actual hardness of the wood.
Hardwoods have broad leaves.
Softwoods are mostly conifers with needles.
Balsa is a hardwood. It is one of the softest, if not the softest woods.
Butternut and willow are domestic hardwoods that are softer than mahogany.
Southern yellow pine is a softwood. It can be as hard or harder than oak.
There is a fundamental difference between the structure of hardwoods and softwoods. Softwoods have cells that are basically rectangular. That means that much of the stiffness of softwoods occurs when the grain is perfectly vertical or horizontal. Under those conditions, softwoods tend to have a higher stiffness-to-weight ratio (or velocity of sound) than hardwoods.
Softwoods also tend to have a greater difference between the cross-grain stiffness and the stiffness along the grain. In a flat top guitar, that means that the softwood top will resist the torque on the bridge without being so stiff across the grain that it restricts vibration.
OTOH, hardwoods have cells that are basically circular, meaning that the stiffness does not vary much due to the verticality of the grain. Hardwoods are much stiffer across the grain for their density than softwoods.
In general, stiffness of wood is roughly proportional to the density. But the stiffness of a plate is proportional to the cube of the thickness. That means that on an instrument top (where the thickness can be varied), the best stiffness-to-weight ratio can usually be attained with the lowest density woods.
Mahogany tops have been popular for a long time...certainly back to the 1930's when Martin was making style-17 guitars for the budget-minded player. Mahogany is not that much denser than spruce, and it does have more cross-grain stiffness. Using similar construction, that would tend to favor a brighter sound. But mahogany does have slightly higher damping than spruce (as do most medium density hardwoods), and that, coupled with the slight extra weight, can produce a darker sound.

[dirkronk]

Has any form of pine ever been used? Or does it too have too much oil/resin/whatever (like teak) to be an effective soundboard? Maybe just too soft, period, to resonate properly?

As to the oil or resin thing, I've always wondered about cedar. I've never built instruments, but toward the end of college I spent a couple of months being a carpenter's assistant up in Massachusetts, where cedar shakes were the siding (not roofing) choice in the area where my friend's house was going up. I was camping out on the site (there'd been material pilferage and I was playing watchdog) and I started many a camp/cookfire with cedar splinters. They had so much resin that they'd catch fire easily, burn hot, and pop and send out sparks like crazy when flames hit one of the many tiny knots in the wood. So is some special drying or oil removal process used to make cedar good for soundboards?

Dirk

[steveyam]

Originally Posted by dirkronk

Has any form of pine ever been used? Or does it too have too much oil/resin/whatever (like teak) to be an effective soundboard? Maybe just too soft, period, to resonate properly?

As to the oil or resin thing, I've always wondered about cedar. I've never built instruments, but toward the end of college I spent a couple of months being a carpenter's assistant up in Massachusetts, where cedar shakes were the siding (not roofing) choice in the area where my friend's house was going up. I was camping out on the site (there'd been material pilferage and I was playing watchdog) and I started many a camp/cookfire with cedar splinters. They had so much resin that they'd catch fire easily, burn hot, and pop and send out sparks like crazy when flames hit one of the many tiny knots in the wood. So is some special drying or oil removal process used to make cedar good for soundboards?

Dirk

I've never understood why you lot make houses out of wood!

[slinco]

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[dirkronk]

Originally Posted by steveyam

I've never understood why you lot make houses out of wood!

Agreed. Well, sorta. I came back from Massachusetts to Texas with a firm conviction never to use cedar shakes on any house I'd ever own. FWIW, my house today is faced with cut stone.


Dirk

[John Arnold]

Has any form of pine ever been used? Or does it too have too much oil/resin/whatever (like teak) to be an effective soundboard? Maybe just too soft, period, to resonate properly?

Pine, particularly the softer varieties, makes a decent soundboard. Ponderosa pine and white pine are two types that are in the same density range as spruce, but neither has the strength of spruce.

As to the oil or resin thing, I've always wondered about cedar.

Resins can be problematic, and careful heating of the wood will help remove the excess, as well as harden the pitch in coniferous woods.
The most common cedar used for soundboards is Western red cedar, and it seems to have less oil than many other types.
The all-cedar guitar I built had Eastern red cedar back and sides, and an incense cedar top. It was built in 1985, and no oil problems so far.

[rlgph]

I have a McCollum with a Spanish cedar top and olive B&S. Spanish cedar is a hardwood (not a cedar), and is commonly used for guitar necks. The guitar tone sparkles, with excellent overtones, and is slightly bright (at least in comparison to my all koa Santa Cruz).

[dekutree64]

Originally Posted by MBE

An interesting point made by the OP is that we don't see mixing of hardwood tonewoods that we know sound good.

A Koa top, rosewood (or coco, or ziricote, or blackwood) back/side guitar would be absolutely stunning visually in my opinion.

I've thought this as well. Curly koa with Indian rosewood back/sides is on my to-do list

Here's another cool one that I just remembered, by Ken Casper. Work in progress, but it's quite beautiful. Butternut top, with black walnut back/sides http://www.luthiersforum.com/forum/v...=10101&t=36064
Butternut is similar density to Spanish cedar, although much less common in sizes large enough for two-piece quartersawn guitar tops.

Originally Posted by rlgph

I have a McCollum with a Spanish cedar top and olive B&S. Spanish cedar is a hardwood (not a cedar), and is commonly used for guitar necks. The guitar tone sparkles, with excellent overtones, and is slightly bright (at least in comparison to my all koa Santa Cruz).

Got any photos/videos/audio clips of that? I'd love to see and hear it. I've wondered why mahogany is so much more commonly used for tops, when Spanish cedar is about the same price and lighter weight. Seems like a great top wood.

[Wade Hampton]

Originally Posted by dirkronk

Has any form of pine ever been used? Or does it too have too much oil/resin/whatever (like teak) to be an effective soundboard? Maybe just too soft, period, to resonate properly?

I've spent some time playing music onstage in Scandinavia and Russia, and playing music offstage with local musicians as well, whenever the opportunity arose. The Russians in particular have a long tradition of using pine and larch for the soundboards of their various stringed instruments. The Swedes, too, though they generally have access to (and a preference for) spruce. But Swedish folk instruments with pine soundboards are not uncommon.


Wade Hampton Miller