Engineered braces

[gitnoob]

Originally Posted by HCG Canada

Physics.

Yes, spruce braces do transmit sound, but so does the top.

So by gluing the braces to the top, you're not changing the material density.

You're adding mass, which by itself will decrease amplitude and frequency.

And you're adding stiffness, which will increase frequency.

[KevinLPederson]

some people are innovative and don't "market it". They don't necessarily want to create a "prejudice" against their product. They let the guitar speak for itself - so to speak .

As Mr. Carruth has stated in other posts - bracing is structural "first" - "acoustic" second - or something to that degree. In electricity resistance is measured in Ohms...bracing could be "paralleled" with this (but not technically). The least amount you need to do the job - according to its stiffness. HOW you do it - is "your thing".

Have a good day.

Kevin.

[Ned Milburn]

Originally Posted by gitnoob

Yes, spruce braces do transmit sound, but so does the top.

So by gluing the braces to the top, you're not changing the material density.

You're adding mass, which by itself will decrease amplitude and frequency.

And you're adding stiffness, which will increase frequency.

Yes, and the increased mass increases the amount of molecules and atoms bumping into each other. As Alan C. mentioned and alluded to in his post, the braces are shaped to help allow the top to flex in the right spots and to the desired amount, and it is every guitar builder's challenge to balance his/her brace thicknesses, shapes, heights, and scallops to fit within his/her chosen bracing pattern.

Tapping a non-braced top that is at final thickness is similar to tapping a piece of paper. It makes a "flomp" type of sound (a bit of exaggeration here for illustrative purposes). Tapping a braced top before even it is attached to the guitar should produce more of a bell like sustaining ring.

Think of a miner trapped in a mine with no communication to the above world other than a metal pipe. This pipe can be tapped with a hammer or other hard object to create a bumping-molecule sound wave that doesn't "whip" the pipe to transmit the sound, but the sound transmits none-the-less. Little of the sound will be transmitted to the air. For this, a diaphragm is necessary.

Gothic cathedral window profiles braces are common, if not standard. This yields great strength (height) and at the same time retains a spatial volume of wood through which sound waves can travel. Ovation tried bracing with T-shaped braces at one time (similar gluing surface area as "standard" braces since the top of the T is glued to the soundboard, and similar overall stiffness due to the similar height compared to standard braces, but less mass since a portion of wood left on the brace in a round-topped or gothic window shaped brace is removed). This bracing pattern didn't seem to help Ovation guitars yield a super tone. Nor did it seem to help their structural longevity (I have seen several Ovations with collapsing and warping tops).

Does the amount of sound transmitted through the braces by bumping molecules contribute as a main factor to the sound of an instrument? I think likely not. But can we deny that this is a factor in the sound transmission of an instrument? I believe not. It is my belief that bracing can help add to the immediacy of sound energy transmission of the vibrating strings to all portions of the soundboard, thus enhancing its immediacy of attack.

Along this concept is cedar vs. spruce. Sound waves travel more quickly through spruce than through cedar. This can be measured, and has apparently been measured. This explains the general "rounder" or "softer" or "less bright" sound of cedar topped instruments, since the attack of the note is spread out over a longer period of time when compared to a more immediate attack from spruce that transmits sound more quickly. We are talking milliseconds, here. If you have ever played electric with very small amounts of delay effect on the sound, blended with the original sound, you can understand clearly how adding even 10 to 20 milliseconds of delay can help create a rounder and softer attack than the pure, non-delayed, sound. (I studied jazz in university and played jazz guitar in Montreal up to 5 and 6 nights a week - albeit not all paying gigs - I was after all a student then. Point is, modern jazz guitarists often use delay in their sound for the reasons I mention above. I spent hours upon hours experimenting with different delay lengths and mixes to tweak the sound to an attack that was pleasing to me.)

And before someone flames me for mentioning cedar vs. spruce, it must be said that a softer top can be mitigated by a different balance in the bracing pattern. So, a skilled and knowledgeable builder should be able to build a spruce and cedar guitar that sound very, very similar.

Again, it is my belief that the physical spatial volume of the braces has an impact on the sound of an acoustic guitar. The effect is likely not of overall sound volume but likely more so on the attack of a note and the colour of the overall tone.

Just my 1.87 yen, FWIW. ;-)