Hardwood audio rack

What do you mean by "burred"? Hardwoods are classified for grain by porosity, i.e. either open or closed. Oak, for example is open grained, maple and mahogany are closed. Are you referring to rough-sawn? Hardwoods are also classified by density which would be more important to your idea of dispersion.
Check the threads on "shelves" here where there is a lot of discussion on maple. You might also want to look at the American Hardwood Association web site. Acoustical properties of wood flooring is important to architects and a web search for that might yield some results.
I have built a "flexy rack" with 1 1/2" thick maple shelves, see the Red Kiwi rack thread and find maple is much more neutral than MDF. Good Luck and feel free to contact me directly.

Maple is the best hardwood for audio racks. It is VERY dense and non-resonant. Rock maple is better, but very hard to work. Zothecus makes their rack frames out of maple so you might want to take a look at their stuff for ideas.

Wood technology is a science like any other. If interested, R. Bruce Hoadley is generally recognised as the expert and his books are quite readable. Briefly, wood density is a function of specific gravity, the density relative to water, and if you consult a chart you will find that densities overlap between so-called hardwoods and softwoods, i.e., southern yellow pine is more dense than walnut. Hard and soft really pertain to grain structure, not density. A complicating factor is that wood exhibits different growth characteristics during the growth season which causes early growth, sapwood to be less dense than late growth, heartwood. Pine heartwood is up to 3 times more dense than it's sapwood. maple is considered "hard" because there is little difference between early and late densities which is why it exhibits little "grain". Perhaps that is why it is judged to "sound" better. There is no species called "rock maple", that is a marketing term for any hard maple used in the construction of items like mitre boxes. All maples work quite well with carbide tipped tools and cut cleanly with little shearing or fuzzing.
Perhaps one might try holding a tuning fork to various woods and somehow measuring the resonance they store or reflect. In any event, from the cabinetmakers viewpoint, wood should be chosen for it's beauty and suitability for joinery in a given application and the tweaking left to pods, cones and wires. JMHO.

Correct, Maple is the way to go!