what is the theory behind maple stands and racks?

The way I understand it the maple will not pass the vibration on, as it is so dense and has so much mass that it is very hard to get it to vibrate at all. I have Know idea what happens to the vibration given off by the component it self. Now you have me reading more to find out what happens on that side of things. I will do my best to find an answer.

My guess is that the wood "absorbs" the vibration, just as your house absorbs and dampens noise (to a greater or lesser degree). The thicker and heavier the wood, there greater its ability to absorb and dissipate vibration from either direction. I am sure certain woods are better at this than others.

Ok this is what happens. Your amp stand carries the vibration to the spikes and they in turn disperse it into the floor.Maple does not absorb vibration what so ever it acts like a conduit carrying it away.When the vibration reaches the softer pine in the floor it is absorbed. The pine being the subflooring and joistes.That is why baseball bats are not made of maple it would carry all that energy into your hands.Ever hit a ball and gotten that sting well the bat carried the vibration instead of absorbing it. Ash absorbes vibration thats what bats are made from. Thakyou Cyclonicman I needed that investagation to keep me interested in audio.Some times I get bored and take crap forgranted.

Does that mean that, at least in principle, ash platforms may be preferable to maple platforms? G.

You know its fishing season here in Oregon and even tho its a slow year there's lots of out of work people trying to catch dinner. Well, I went to the local fishermans supply store with the same notion in mind until I came across a bunch of lead weights in the shape of doughnuts called sand dollars. They ranged from 4 to 10 ounces. Naturally my mindset shifted to the potential of for these toxic beautys as audio vibration isolators, so I scooped up 8 of the 6oz weights and some 1.5" cork bobbers and forgot all about fishing.
Back home I went to waste another weekend with obsessive experiments. The guilt soon vanished as I found audio nirvana in a funky configuration that was insightful about vibrations both coming and going from my system. It may be germaine to this discussion.

My Primaluna CD player rests atop 2 inches of maple plywood and mdf. It sounds great but gets little use since hddtv dvr and plasma caught my eyes.
Anyway, If your not familiar with it, the primaluna8 is a tube hybrid cd player with a nice heavy chassis and some beefy rubber feet. I recently swapped the power chord out with a CCAC silver one and rolled the tubes for the first time to some NOS ones that came with it but I had never tried,the improvments were beguiling and compelled me to see what else I was missing out on..
So I started balancing the player on various things. I tryed the dali speaker spikes and their bases. It was an improvement, but the biggest improvement came when I balanced the player on 1.5" smashballs resting on the lead dougnuts. The players big rubber feet have a cavity in the center that somewhat fit the smashballs. The smashballs are quite squishy or resiliant, and so reduced to 1" in height. and the lead sat atop the maple. The lead seemed to act as a heet sink and the air cushion of the ball under stress seemed to insulate the player from ground vibrations coming the other direction.
So long story long, I think you a right, mass matters.
What was cool about this setup was it is a very delicate balancing act and one can see the effects of vibration by simply walking up to the player, the balls would start to roll off balanc.
By the same token the vibrations coming from the player could also move the balls out of alignment. eg I got the balls perfectly aligned under the feet and in the lead doughnuts, turned it on and sat down to listen, After a time the balls would move. I know they are under constant pressure to push back just from being squashed, but the they moved more when a cd was playing.

Bottom line is the improvements were huge with an air cushion separating sources of vibration and the density of the lead as an asorber was astoundingly better than just the balls on the maple itself.