What kind of scientific proof do you need? It is scientifically proven how vibrations are altered by coupling them to a mass, a mass with a specific resonant frequency, frequency dampers, etc. Specific weight of various wood species is well known. The effect of mass on resonant frequency is well known. The effect of two systems with different resonances interacting has been studied ad nauseum. Don't you believe that the strings resonate? Don't you know that the body resonates too? Don't you know that because one is coupled to the other, they interact.
It's no use saying that the sound only comes from the pickup sensing the string vibration. That's true but the string's vibration is being altered by the system it is coupled to. Alter the string's vibration by robbing it of overtones that are being absorbed by coupling to the body, and the pickup will not put those frequencies back. It only sees what is being delivered to it - by the strings' vibrations - that are being altered by the mass they are coupled to.
I want double blind trials with sample sizes of at least dozens. More would be better. A sizable control group is also required. Anything less is anecdotal. Ash vs mahogany. Rosewood vs maple. I withhold belief in any difference without scientific evidence. I am an a-tonewoodist.
What you are asking is pointless. You don't need double blind tests to understand the science I was talking about. It has been proven. Correct me if I am wrong in my interpretation, but what you seem to be saying is that you don't believe it. OK but the evidence is overwhelmingly against you.
I think Gorn and Turnaround are arguing two different sides of the question:
There shouldn't be any question whether different species of wood affect the vibration of a string afixed to an object composed of that wood differently, for the reasons Turnaround cited. Physics is your friend. We know that the medium impacts the speed of vibration transmissions, that those medium-affected speeds are frequency-dependent, and that skewing the spectral component of a complex vibration -- which is what happens when you alter the density and resonant frequency of that vibration's medium -- is
by definition how we shape timbre. So different species of wood, because they have different densities and resonant frequencies, should impact a string's vibration differently.
But I think what Gorn is asking is simply, how identifiable are those differences? Or perhaps more to the point,
how audible are those differences? (There's a famous quote from luthier John Amaral; when asked which components affect a guitar's sound, he said "
Everything makes a difference. The question is whether you can hear those differences.")
I am
supremely confident that there are measurable and demonstrable differences in the density and resonant frequency of otherwise identical slabs of mahogany and ash. I am also
supremely confident that those differences will impact the behavior of a vibrating string mounted on those pieces of wood in a measurable way.
I am
far less confident that those differences will be audible to a bass playing musician, especially in the context of a full band performance.
But my certainty rises back to the almost arrogant level of
supremely confident that a bass playing musician would not be able to reliably and consistently (i.e., better than chance) identify
which was mahogany and which was ash when listening to otherwise identical instruments, even if [edit: especially if] the auditioning took place in laboratory conditions under true double-blind ABX test protocol.