Rosewood/Mahogany "tweener" tonewood

[Alan Carruth]

'In between' in what respect?

Quartered oak has density and stiffness that are much like Brazilian rosewood, but damping that's closer to maple. Black locust has density that's more like Indian rosewood, but higher stiffness and lower damping, from what I've seen. Black walnut and soft maple are almost the same in the things you can measure, but they don't look the same, and people insist that they sound different. It's sort of like the old bumper sticker: "You are a unique individual, just like everybody else". Can we sort out which differences in wood properties affect what aspects of tone? Maybe, eventually, assuming we can get people to agree on what those tonal attributes are. I'm not holding my breath.

Under the circumstances, it might well be that you'd get the most satisfactory results by telling a good luthier just what you mean be 'in between' tone, and then turn them loose in the lumber room. Alternatively, you could go out and play a lot of guitars made of various alternatives by different makers/factories, and see what you like. Don't expect everybody to agree with your choice.

[printer2]

Originally Posted by printer2

I have been thinking about this and am wondering how much the back bracing can dampen down the back resonances. I can see if the back plate has low dampening and the brace ends are tapered enough that the plate's characteristics dominate. As the braces are left heavier towards the ends do they start to dominate due to the increase in stiffness or is the plate still the big dog on the block? That is if it has low dampening.

Or in other ways, can you have a higher Q piece of wood and dampen it down? Can't see going the other way, a low Q plate and bracing controlling the damping. Maybe a low mass back plate and higher mass bracing? Don't know, trying to figure out the relationship between the two elements.

The English can change but the questions remain the same. I don't have enough experience yet to answer them, thought somebody else may be able to shed some light.

[Chipotle]

Originally Posted by Alan Carruth

'In between' in what respect?...

Under the circumstances, it might well be that you'd get the most satisfactory results by telling a good luthier just what you mean be 'in between' tone, and then turn them loose in the lumber room. Alternatively, you could go out and play a lot of guitars made of various alternatives by different makers/factories, and see what you like. Don't expect everybody to agree with your choice.

Very good point, and a discussion with the luthier will be important. I think the main continua would be Overtones <--> Fundamental on the one hand, and Sustain <--> Damped on the other. Obviously different woods will fall at different points along either of those.

But since it's difficult to find any guitar at all to play in some of these woods, especially comparable models, I thought I'd throw it out here. I've tried guitars (all spruce top) in koa, maple, myrtle, various rosewoods and mahoganies.... I'd love to play guitars with bubinga, blackwood, ziricote, ovankol, etc. but it's pretty unlikely. Some I'd never even heard of (Palo Escrito), much less knew they made guitars out of them. So I appreciate the ideas.

[Ken Franklin]

Taylor uses ovangkal a lot so you should be able to get a hold of something there. If it's too thick it can yield a harsh sounding guitar to my ear. Of your list I like bubinga and ziricote a lot. As far as fundamentals vs overtones goes different top woods on my guitars have had a greater effect than the back or side woods.

[Truckjohn]

The other thing to take into consideration is that the luthier has quite a bit of leeway to push the sound this or that way....

That's not going to completely make a substitution of one wood for another... I mean... If you want a Mahogany guitar - mahogany is the logical place to start, not Cocobolo.....

But it certainly can push the balance one way or the other. Features like light or heavy sides, the bracing scheme, bridge, bridge plate, scale length, and a live back or not can push a guitar's balance somewhat in favor of one or the other direction.

And a good luthier could do that with many of these in between woods.

Thanks

[Truckjohn]

Originally Posted by justonwo

Imagine a device wherein a capillary tube full of water is affixed to a mechanical oscillator. The end of the capillary tube makes contact with a sponge when the oscillator reaches the end of its travel. The momentary contact between the capillary tube and the sponge causes the sponge to absorb a small amount of water. The entire apparatus is located in a heated room that causes the water to evaporate from the sponge relatively quickly after the capillary moves away from the sponge. If one were to plot the dampness of the sponge vs time, one would observe a wave of sorts where the dampness of the sponge increases when the oscillator makes contact and then decreases as water evaporates from the sponge. If the oscillator timing is adjusted properly, this wave will have a constant amplitude.

Now the capillary tube is affixed to a tank of water. Into the water is dripped a fully water soluble, low vapor pressure liquid - let's say glycerine - such that over time the viscosity of the liquid in the tank increases and the amount of water absorbed into the sponge by capillary action decreases during each successive contact with the sponge. The resulting plot of dampness of the sponge vs time would then show a decrease in amplitude over time.

As a result, for this specific apparatus, the glycerin drip can be said to damp the dampening of the sponge.

And if said system was connected to a louver in a duct to control the flow of air between 2 rooms.....

You could say that the glycerin drip was damping the dampening of the damper....

And if said system sprung a leak....

You would be damping the dampening of the damp damper....

[justonwo]

Originally Posted by Truckjohn

And if said system was connected to a louver in a duct to control the flow of air between 2 rooms.....

You could say that the glycerin drip was damping the dampening of the damper....

And if said system sprung a leak....

You would be damping the dampening of the damp damper....

Brilliant!!! I love it.

[redir]

This is a no brainier. You make the back out of a panel of rosewood and a panel of mahogany. Then you make the sides out of a panel of rosewood and mahogany and assemble it in an opposite Harlequin fashion.

Voila - In between.

[Mark Hatcher]

Originally Posted by redir

This is a no brainier. You make the back out of a panel of rosewood and a panel of mahogany. Then you make the sides out of a panel of rosewood and mahogany and assemble it in an opposite Harlequin fashion.

Voila - In between.

I think this is the second time this has been offered as a solution. I have to ask given the different vibration characteristics they each have, how do you decouple the two halves of the back so they don't dampen each other? And if you do manage to decouple them how do you get back all of the lower resonance you'd lose in this arrangement?

[Howard Klepper]

Originally Posted by justonwo

Imagine a device wherein a capillary tube full of water is affixed to a mechanical oscillator. The end of the capillary tube makes contact with a sponge when the oscillator reaches the end of its travel. The momentary contact between the capillary tube and the sponge causes the sponge to absorb a small amount of water. The entire apparatus is located in a heated room that causes the water to evaporate from the sponge relatively quickly after the capillary moves away from the sponge. If one were to plot the dampness of the sponge vs time, one would observe a wave of sorts where the dampness of the sponge increases when the oscillator makes contact and then decreases as water evaporates from the sponge. If the oscillator timing is adjusted properly, this wave will have a constant amplitude.

Now the capillary tube is affixed to a tank of water. Into the water is dripped a fully water soluble, low vapor pressure liquid - let's say glycerine - such that over time the viscosity of the liquid in the tank increases and the amount of water absorbed into the sponge by capillary action decreases during each successive contact with the sponge. The resulting plot of dampness of the sponge vs time would then show a decrease in amplitude over time.

As a result, for this specific apparatus, the glycerin drip can be said to damp the dampening of the sponge.

Thanks, Juston, for a great illustration of why we need to keep the two words distinct.

[redir]

Originally Posted by Mark Hatcher

I think this is the second time this has been offered as a solution. I have to ask given the different vibration characteristics they each have, how do you decouple the two halves of the back so they don't dampen each other? And if you do manage to decouple them how do you get back all of the lower resonance you'd lose in this arrangement?

That kind of thinking is above my pay grade

But it would look interesting and the marketing department would have a solution to a serious problem.

---

Here's a little not so well known secret. The reason why mahogany and rosewood guitars sound so good is because there were a lot of good mahogany and rosewood guitars made. That's about it in a nut shell.

[justonwo]

Originally Posted by Howard Klepper

Thanks, Juston, for a great illustration of why we need to keep the two words distinct.

I thought you would get a kick out of that.

[Alan Carruth]

The 'bass' and 'treble' sides of the guitar are useful in describing where the differently pitched strings are, but not where the sound comes from. Low pitches are generally the product of large areas and masses vibrating as a whole. The low range of the guitar, from about the low E up to the open G string or a bit higher is the 'bass reflex range', where the air in the box acts as a Helmholtz resonator, while the entire lower bout is working like the speaker cone in a woofer.

As you go higher in pitch than that things get more complicated. The top, and the air mass inside, break up into smaller parcels. For example, the next 'air' resonance up from the Helmholtz-type 'main air' mode is sometimes called the 'lengthwise bathtub' mode. The air can be thought of as 'sloshing' along the length of the box, with high sound levels internally at the neck and tail blocks, and a sound 'null' somewhere across the middle between the bridge and the sound hole where the energy is in flow rather than pressure change. You may or may not heart this in the sound directly. It tends to come in at around 350 Hz (F on the high E), but doesn't communicate strongly with the hole usually. On the other hand, it can couple with a top resonance that often occurs in the same pitch range, and that can lead to 'interesting' consequences.

The higher up in pitch you go, the more areas the top and air divide up into, and those get smaller and smaller. What you hear coming from the guitar is, in a sense, a sum of all of those things acting in that direction. Again, most guitars have a 'cross dipole' top resonant mode, say, around 300 Hz (D on the B string). As the 'treble' side of the bridge moves up, the 'bass' side goes down. This is not an effective sound producer since the two halves of the top tend to cancel each other out. However, since that motion is also superimposed on the speaker-like 'main' top motion, that adds or subtracts from the sound output on either side of the top. The result is that, between the pitches of the 'main' and 'cross dipole' resonances string on the bass side producing that pitch will sound loudest from the treble side of the top. However, as you go higher in pitch the loud side suddenly switches to the bass side of the top as you pass through the dipole pitch. The higher you go in frequency, the more of that sort of directional stuff is going on. Some of the very high pitches only produce sound over very narrow beams in front, or to the side, of the guitar.

In short, this is one of those cases where simple explanations, no matter now appealing, are wrong.

[TomB'sox]

Originally Posted by Alan Carruth

The 'bass' and 'treble' sides of the guitar are useful in describing where the differently pitched strings are, but not where the sound comes from. Low pitches are generally the product of large areas and masses vibrating as a whole. The low range of the guitar, from about the low E up to the open G string or a bit higher is the 'bass reflex range', where the air in the box acts as a Helmholtz resonator, while the entire lower bout is working like the speaker cone in a woofer.

As you go higher in pitch than that things get more complicated. The top, and the air mass inside, break up into smaller parcels. For example, the next 'air' resonance up from the Helmholtz-type 'main air' mode is sometimes called the 'lengthwise bathtub' mode. The air can be thought of as 'sloshing' along the length of the box, with high sound levels internally at the neck and tail blocks, and a sound 'null' somewhere across the middle between the bridge and the sound hole where the energy is in flow rather than pressure change. You may or may not heart this in the sound directly. It tends to come in at around 350 Hz (F on the high E), but doesn't communicate strongly with the hole usually. On the other hand, it can couple with a top resonance that often occurs in the same pitch range, and that can lead to 'interesting' consequences.

The higher up in pitch you go, the more areas the top and air divide up into, and those get smaller and smaller. What you hear coming from the guitar is, in a sense, a sum of all of those things acting in that direction. Again, most guitars have a 'cross dipole' top resonant mode, say, around 300 Hz (D on the B string). As the 'treble' side of the bridge moves up, the 'bass' side goes down. This is not an effective sound producer since the two halves of the top tend to cancel each other out. However, since that motion is also superimposed on the speaker-like 'main' top motion, that adds or subtracts from the sound output on either side of the top. The result is that, between the pitches of the 'main' and 'cross dipole' resonances string on the bass side producing that pitch will sound loudest from the treble side of the top. However, as you go higher in pitch the loud side suddenly switches to the bass side of the top as you pass through the dipole pitch. The higher you go in frequency, the more of that sort of directional stuff is going on. Some of the very high pitches only produce sound over very narrow beams in front, or to the side, of the guitar.

In short, this is one of those cases where simple explanations, no matter now appealing, are wrong.

That's exactly what I was just about to say....

[mcgr40]

I would advise looking/handling a large number of sets of mahogany and rosewood. The differences in tone of the individual examples can be wide.
You can find cuban mahogany from near the keys that is at or above 4 lbs/foot in weight. It can be found with a generally smaller pore and a glassy feel.
But I think you can find very heavy examples of honduran mahogany, also, that would do the trick. It seems more likely to find a denser/glassier mahogany example(just make sure it still has that mahogany sustain), than to find a substitute amongst the other woods.

I don't wish to offend any other woods, I just think it would be easier, to find a heavy/glassy feeling piece of mahogany that would impart some of the overtones of the tweener.