Great pics of Vibrational Modes of stringed instrument at different frequencies.

racman

I thought this was quite interesting and thought others may find it so as well:

http://www.bbc.co.uk/news/science-environment-13573631

Bob-Dubery

Whenever I see these sorts of images they suggest to me that, in fact, you don't lose any tone or volume with a cutaway on an acoustic guitar.

MikeM

VERY interesting. Thanked

VellaJ

That's incredible... Thanks for the post ?

FenderBender

Awesome stuff. Powder was a pretty good idea too IMO ?

Wizard

I've used the powder trick (usually salt) to find the modes on marimba bars.
Have found it to be much more efficient and just as accurate to use a "tapping" technique.
Using a soft mallet, it responds quite differently at the modal points.
These are the "sweet" spots where all of the energy is transferred straight back without setting the bar into action.
Similar to finding the sweet spot on a cricket bat.
Have no idea if a similar technique would work on a soundboard though.

guitarboy2828

X-rated Bob wrote Whenever I see these sorts of images they suggest to me that, in fact, you don't lose any tone or volume with a cutaway on an acoustic guitar.

When I was speaking to Shawn O'Neill about this (He has built several acoustics) he was telling me how anything past the sound hole is pretty much "dead" space, the sound doesn't resonate there. He said that is why some building, ie McPherson put the sound hole where they do.

It makes me wonder.. what would a DOUBLE cut away acoustic sound like? ???

Bob-Dubery

Paul E wrote
X-rated Bob wrote Whenever I see these sorts of images they suggest to me that, in fact, you don't lose any tone or volume with a cutaway on an acoustic guitar.

When I was speaking to Shawn O'Neill about this (He has built several acoustics) he was telling me how anything past the sound hole is pretty much "dead" space, the sound doesn't resonate there. He said that is why some building, ie McPherson put the sound hole where they do.

I started thinking about this after I had a chat with luthier Nick Benjamin a few years ago. He said that he considered the top to be dead up at the shoulders, but thought there was still a small amount of valuable resonance (or reflection) in the corresponding part of the back. I'd think that in most acoustics the mounting block for the neck has quite a deadening effect on that part of the top.

It makes me wonder.. what would a DOUBLE cut away acoustic sound like? ???

You get them (or did get them).

Thompson has a more radically cut double cut away baritone acoustic from the same luthier, Danny Ferrington.

Bob-Dubery

If the top is dead in the shoulder area, then I don't think there's any tonal advantage, or penalty, to a double cut away. It may pose some construction problems though.

racman

Mike Doolin is well known for his stunning double cutaway guitars (including harp guitars):

guitarboy2828

racman wrote Mike Doolin is well known for his stunning double cutaway guitars (including harp guitars):

Those are some sweet guitars!

Back to the original link, the bracing on that acoustic shown was rather interesting wasn't it? It would be pretty awesome to be able to check out the bracing of different acoustics and how they fair with the resonance of each other. I know Somogyi has written entire books on bracing and the part it plays!

Bob-Dubery

Paul E wrote Back to the original link, the bracing on that acoustic shown was rather interesting wasn't it? It would be pretty awesome to be able to check out the bracing of different acoustics and how they fair with the resonance of each other. I know Somogyi has written entire books on bracing and the part it plays!

They were testing nylon string guitars - well that's what those pictures showed. Bracing those is a different ball game from bracing steel strings as there is less stress on the top. Bracing is about strength as well as about tone.

Bracing does make a difference. In the world of steel string flat tops it seems hard to get away from X bracing. However there are still lots of variations as regards positioning and shaping.

guitarboy2828

X-rated Bob wrote
Paul E wrote Back to the original link, the bracing on that acoustic shown was rather interesting wasn't it? It would be pretty awesome to be able to check out the bracing of different acoustics and how they fair with the resonance of each other. I know Somogyi has written entire books on bracing and the part it plays!
They were testing nylon string guitars - well that's what those pictures showed. Bracing those is a different ball game from bracing steel strings as there is less stress on the top. Bracing is about strength as well as about tone.

Bracing does make a difference. In the world of steel string flat tops it seems hard to get away from X bracing. However there are still lots of variations as regards positioning and shaping.

Ahh, I see, that makes sense.. I have seen that nearly everyone uses the X-bracing, wondered why. Now I know ?

Why is there less tension with a steel string? Surely the nylon strings have less tension?

Bob-Dubery

Sorry. I meant that there is less tension with nylon, more with steel.

singemonkey

Wasn't it interesting though that that renaissance guitar had a lot more movement around the shoulders than the Torres design?

BMU

Awesome pictures, thanks for posting.