Scientific study of back woods from JASA

[Dave Bagwill]

Appears to be a rigorous study. Lengthy, but the Abstract at the beginning summarizes the approach to the study and some of the results. There is a pdf version to download if it's something you'd like to save.

https://asa.scitation.org/doi/10.1121/1.5084735

[John Link]

Very interesting Dave. Thank you.

My quibble with the "science" is two fold. They are not large quibbles, though I certainly understand and know that different guitars produce different and often quite distinctly different sounds, due to many different design variations and method of production.

This study whittled the variables down to one, thickness of the sides and backs, adjusted by the hands of a skilled luthier to be the same, functionally speaking. The slight problem I have with this is that there are two variables in the back, the back plate itself, and the way it is braced. They obviated the second variable, even though it is at least conceivable that a good luthier might vary bracing as well as thickness, depending on perception of the actual piece of wood and past experience. But this is an almost academic quibble, the result of my involvement in philosophy and logic in a past life - nothing more than the possibility that excluding the bracing pattern might be important to determining if the side and back wood of a well made guitar makes any difference.

The other quibble is, in actuality, just as much based on science as this study. Once upon a time, a group of experimental psychologists were asked to study the learning capabilities of three different groups of lab rats. The first group was bred to be of average intelligence (for a rat), the other two were bred for above and below average intelligence. The study focused on teaching each group how to run the same maze to get its reward, or maybe avoid getting shocked for taking too long - I can't remember all the details.

What the rat psychologists did not know was that they, not the rats, were the actual subjects of the experiment. The supposed 3 tiered distribution of intelligence was a sham. All the rats were from the same strain, one that had been developed for homogeneity of intelligence. Yet, when the data was collected it turned out that, objectively, the "smart" rats learned the quickest, the "average" rats came in second, and the "dumb" rats finished last.

What to conclude? My take is that the rat psychologists consciously or unconsciously applied different methods, motivation, and effort to the different rat groups, depending on their conception of that group's capability.

The guitar study deliberately made it difficult if not impossible for the players and listeners to know which guitar they were interacting with. It is quite possible that being unable to use this crucial piece of differentiating information contributed to their finding that all instruments were the same. This is quite consistent with Immanuel Kant's theory of knowledge, epistemology if you like hundred dollar words. He held that both the idealists and empiricists had something to offer, except that neither was "right" when they excluded the contribution of the other. That is, direct experience is the result of both the perceiver's take on the world and the object of that perception itself. He had a special name for the extra mental objects (noumenon). He held that directly perceiving noumena was beyond human capabilities, that our perceptions are always colored by our minds, even when we measure, or think we are measuring, as this group of rat psychologists "thought" they were measuring.

And so, my quibble boils down to this: The study is interesting if one takes a pure empiricist's viewpoint, but questionable if one accepts the Kantian position. Personally, I think the Kantian view, applied with intelligent moderation, explains more about how we get through our lives that pure empiricism. Pure idealism, on the other hand, truly sucks, as Sam Johnson aptly demonstrated when he invited Bishop Berkeley to kick a large boulder, since it existed only in Berkeley's mind. The good Bishop, of course, declined, as he knew there was something "out there" that transcended what existed in his mind, and that might break his foot if he kicked it.

My wish is that they had completed the study by ALSO allowing the participants to compare the guitars knowing which wood they were listening to.

[Dave Bagwill]

Thanks John, some good points there. My transcendental unity of apperception is impressed. Not making fun - anyone who has read the first Critique has 'cred' in my book.

In your opinion, do you think the results of the science were reliable? I know the best sounding guitar I've built was good ol' Michigan Walnut, a humble domestic wood, and cannot fathom spending $600 or more on a vanity wood if I was hoping for a better sound. Better looks, of course. Walnut is not 'stunning'

[John Parchem]

I am mixed in my view. I do not think any wood has magical properties, but they do have characteristics, density vs stiffness and Q factor (high Q low dampening, it rings for a long time when tapped). These properties affect how a back built with these woods will vibrate. All of this is demonstrable.

Many commercial guitar designs actually both Steel string and classical are built to minimise the contribution of a back to sound. They are made stiff and heavy. There are reasons, it takes string energy to get the back to vibrate, that energy is finite and is taken from the top. Also the without care the back can have a vibrational mode that not only steals energy from the top but muddies the tops voice.

With care the back can be tuned such that it provides tonal complexity without taking too much energy from the top. I build guitars where I try to achieve that effect. Not all back and side wood have this characteristic. I can hear the difference between my guitars build with a non active back vs an active back. So yes I am sure that a luthier could build a good guitar from any number of tonewoods that they can adjust by intuition or formal tests. But just like top wood, there are tonewood that allow one to utilize its properties to make an outstanding guitar.

Blind listening tests are bullshit in my opinion. Listening is a learned skill. Thailand for example has a tonal language such that they can have up to 6 different words that sound the same to english ears. I learned Thai; it took a lot of time until I could even start to hear the difference. But to them the difference is so striking that they have trouble understanding me even in context. Think of us hearing rape vs hearing reap.

[Dave Bagwill]

Regardless, I'm encouraged to see that over-priced vanity woods are not necessary for an excellent guitar. A good sounding instrument built with quality domestic woods, that plays well and is responsive, is good enough for me. I'm not in a competition, thank goodness.

[John Parchem]

Regardless, I'm encouraged to see that over-priced vanity woods are not necessary for an excellent guitar. A good sounding instrument built with quality domestic woods, that plays well and is responsive, is good enough for me. I'm not in a competition, thank goodness.

I agree completely there is no correlation between the price of the wood and its tonal properties. I have found Osage Orange as the same tonal qualities of the best Rosewoods. Also it is possible to build a great sounding and looking guitar with dang near any stable wood for the back and sides.

[peter havriluk]

This is encouraging and amusing to me. I am in early days of scratchbuilding, two instruments completed and a third under construction, during the past 12 months. Tops out of a bargain box from Alaska, b/s from bargain purchases from RC Tonewoods. The two that I built so far, and these are the first two scratchbuilt guitars of mine, cost me less than $150 each, sitting on a stand ready to play. I'm just delighted. There's such immense personal rewards from learning to play on instruments I made from scratch. And they sound really nice, too. Happy accidents, no doubt, but I sold the GS Mini I'd been using as a student guitar, my own sound nicer, to my ears, and as we all have come to know, care and attention to fretboard and bridge and adjustments result in happy playing guitars. I was really pleased when folks who played my two projects praised their intonation. I'm not able to take advantage, but the guitars are not limited to cowboy chords.