The speed of sound in Spruce wood

Subject: The speed of sound in Spruce wood
From: Donuel
Date: 25 Oct 20 - 10:43 AM

I was surprised the speed of sound in spruce is 3000 to 5000 meters per second, this is faster than many metals!
There are many other factors determining acoustic qualities in wood including complex equations, density, longitudinal grain vs. horizontal, Q factors?, varnish and hardness...
Glass transmits sound at over 4,500 meters per second.
Water transmits sound better than air allowing whals to hear each other 100 miles away. At the ends inside a parabala one can hear a whisper 500 feet away...anyway acoustics has many surprises.

In instruments flat spruce is LOUDER than arched wood. Having been around violins to basses for a lifetime. I have accumulated knowledge that is as direct and simple as giving a tap and having a good feeling which is alot more simple than math. I can still be wrong but at most 10% of the time.
I've experimented with the lightest most conductive materials to the heavier densities of carbon or aluminum. Recently I have found a way to coat spruce with glass instead of varnish or laquer. It is only 2 microns or more thick but due to density and hardness acts like a material 100 times thicker. The glass can be either high gloss or matt. It has the abilility to ring. It matches the speed of sound in spruce and believe it or not is easier to work with and cheaper than all the old methods of finishing.

I am entering phase two tests on instuments rangeing from an unvarnished; cello, violin and Martin guitar. Sometimes you can't improve upon nature and sometimes you can but my intrepid nature to try is hopefully on my side. I'd settle for 0-10% improvement since economics is already on my side.

Subject: RE: The speed of sound in Spruce wood
From: GUEST,gillymor
Date: 25 Oct 20 - 11:44 AM

So when the soprano hits that high C does the instrument shatter in your hands. Of course it might just give it that finish checking that a lot of people find attractive in old Gibsons.
Either way be sure to use safety glass so no one gets hurt.
I'm done now.

Subject: RE: The speed of sound in Spruce wood
From: GUEST,gillymor
Date: 25 Oct 20 - 12:01 PM

Seriously though, I found that the best finish soundwise on a guitar is no finish at all. I used to play at a bluegrass jam and a guy there had scraped off the nitro finish on his '50's D-18 Martin and then applied nothing more than sanding sealer and it suddenly became a cannon. I tried the same with an inexpensive Laguna and had similar, though not quite so dramatic results.

Subject: RE: The speed of sound in Spruce wood
From: leeneia
Date: 25 Oct 20 - 01:59 PM

This is interesting. Thanks for the info.

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 25 Oct 20 - 03:01 PM

I like mellow tones over the too bright sound. I dunno if there will be any effect. I always thought secret varnish and ground arguments were missing the point over the nature of the wood.
I have no proprietary concerns so here is how it is done. The new liquid ceramic glass product with a hardness of 9 or 10 is what I use. It takes 24 hours to cure. The science of new materials has outliers like me who will try all sorts of new applications. So far so good since once hard, the glass is also fire proof.
On a summer day or 78 F indoors the ceramic will dry enough in 10 minutes to polish but 24 hours to harden. In lower temps it could take an hour before polishing.
I have used it on cars, marred glass, windshields, prescription glasses, toilets, sinks - all with great effects. On unvarnished wood I may have to spray a thin coat of matt varnish for an even coating /absorbtion. Then again I may ruin 3 perfectly good instruments. Some of my invention mistakes are as bad as the original Hubble mirror, which is still up there. By sanding 1/12,000th of an inch I should be able to undo a wood mistake. It also looks like I could marinate wood until it totally permeates with unknown results. The elements of this glass is Si O2, yup real glass. Remember Spruce is the real acoustic miracle.

I remember Ben Franklin's glass harmonica invention, wow what a pure tone. :^]

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 25 Oct 20 - 03:19 PM

I don't know what a nitro finish is but I know how an old Paris School French JBV violin is like a cannon compared to new instruments. Some techniques do add a third more tone and volume.

Subject: RE: The speed of sound in Spruce wood
From: GUEST,gillymor
Date: 25 Oct 20 - 04:23 PM

"Nitro" is shorthand for nitrocellulose lacquer, which is what most guitars have been finished with since the 1920's though hand rubbed varnish has had a resurgence in higher end acoustics of late.

Subject: RE: The speed of sound in Spruce wood
From: Jack Campin
Date: 25 Oct 20 - 05:51 PM

Spruce is anisotropic. The speed of sound along the grain will be different from that across it. Coatings will even the difference out, which might not be good.

Soundboards on good Turkish ouds are left bare.

Subject: RE: The speed of sound in Spruce wood
From: EBarnacle
Date: 26 Oct 20 - 12:29 AM

While I am not a fan of urethane varnish for marine purposes, I wonder how its characteristics compare with the tung oil varnishes as an instrument coating. It is definitely a harder surface. One differences is that it polymerizes. I believe that it incorporates atmospheric water into its linkages as it cures.

Subject: RE: The speed of sound in Spruce wood
From: Helen
Date: 26 Oct 20 - 02:34 AM

All I know about spruce is that it is the preferred wood for the soundboard on a Celtic harp and I think it makes a difference which way the grain runs.

Subject: RE: The speed of sound in Spruce wood
From: Mr Red
Date: 26 Oct 20 - 04:01 AM

Donuel - do you need to put yer glasses on to play musical instruments?

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 26 Oct 20 - 08:58 AM

I really don't have hope of improved acoustics from a 2 micron coating of glass. I hope it can forgo the use of thick varnishes that inhibit spruce acoustics. It shines up nicely and is very protective. You know a micron is a millionth of a meter. A human hair is 70 microns. 100 year old spruce is more 'alive' acousticly than 10 year old spruce. The empty spaces inside spruce (vesicle cell walls) are what makes the improved difference imo.

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 26 Oct 20 - 09:18 AM

Spruce conducts sound as fast as steel and is more efficient.
https://www.engineeringtoolbox.com/sound-speed-solids-d_713.html

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 26 Oct 20 - 10:13 AM

Like gillymore mentioned "let thick varnish get out of the way and let spruce do its work"

A micron or two
won't matter to you
when you use glass
the sound is still fast

Subject: RE: The speed of sound in Spruce wood
From: gillymor
Date: 26 Oct 20 - 11:00 AM

To be clear "gillymor" (note spelling) did not write, "let thick varnish get out of the way and let spruce do its work". In a Bluegrass jam volume is essential because you're trying to be heard, and even hear yourself, amongst a bunch of banjos, mandolins and fiddles and not all of them quiet down when you take your solo so volume is important in that context and tone takes a back seat. Luthiers use the various kinds of finishes to alter and hopefully enhance the tone of an instrument and sometimes select the type of finish to complement the characteristics of a particular instrument. I have some fine hand-crafted instruments and would not think of sanding them down to raw wood. Here's some comments from Dana Bourgeios on the subject (I'm lucky enough to own one of his fine guitars):

"The trick is to select a finish that best compliments a guitar’s design and voicing considerations, and to apply it in a way that damps undesirable frequencies, but doesn’t damp desirable ones."

"I try not to judge the relative merits of varnish, lacquer, urethane, polyester, and other finishes, for much the same reason that I cannot say Adirondack spruce is superior to European spruce, or that Brazilian rosewood is always a better choice than mahogany. Like tonewoods, a finish can only be judged in the context of a specific application."


acousticguitar.com

Subject: RE: The speed of sound in Spruce wood
From: Donuel
Date: 26 Oct 20 - 12:05 PM

Interesting that damping is considered for some builds but not all.

On a different note; 20 years ago I found a foam that transmits high frequencies better than air with no perceivable loss. You would think foam would deaden sound but this stuff seems to magnify sound by just touching the stuff. It is a formula once used for shipping. I used it inside cellos connecting top to bottom at various regions and it improved the sound. This is not for guitars because they don't work that way. If you know what linings are, the foam is great for the top plate with a piece going front to back on the left upper or middle bout. Its good for instruments that are too mellow nd improve inferior instruments. I use hide glue around the edge of the 1 inch lining and allow foam to directly touch wood as much as possible.

2 other things I found important such as a bevel around the the edge of spruce at the rib connection as well as thin ribs all around especially at the bottom. I think of the spruce like the cone of a speaker - flexible at the edges. The maple is the box of the speaker.

I have eclectic tastes and am not a graduate of a luthier school.

Gillymor I do not sand down fine finished instruments to bare wood. I am using unfinished (white wood or stained) instruments to experiment.

Subject: RE: The speed of sound in Spruce wood
From: gillymor
Date: 26 Oct 20 - 12:17 PM

I didn't say that you did "sand down fine finished instruments to bare wood". I was just making it clear that I never said "let thick varnish get out of the way and let spruce do its work".

"g"illymor