The main reason why suspending or decoupling your turntable from the floor works so well is as Paul said: positive feedback from the speakers, through the floor and air into your turntable, and back to the stylus, colours the sound. In the worst case, at high volume levels, the feedback will be so bad that howling is set up. Try turning the turntable off, rest the stylus on the record, turn the volume up, and give the record a slight tap, to see what feedback causes. That’s why a number of turntable manufacturers back in the 1970’s, such as Linn, Thorens and AR had better sounding turntables than ones with no suspension, because their suspension cancelled out most of the vibration from the speakers getting back to the stylus of the turntable. Coupling your turntable back to the speakers by solid supports, whether they are spikes or not, is not good. The way to stop turntable motor vibration from getting back to the stylus is by having the tonearm and platter decoupled from the motor on their own floating base, by a suspension system, like Linn (Sondek) or other belt drive turntables often do; or decoupling the motor via rubber mountings, as Rega (Planar 3) and many other manufacturers, including many Japanese belt drives, used to do; or making the motor relatively vibrationless, as Rega (P3/5/7) do now, or as the Japanese (like Technics) do with their low (platter) speed, direct drive motors (e.g. Technics SL-1200). Manufacturers also often make their more expensive turntables from materials which don’t resonate much, which is why acrylic and glass platters are often used these days, and acrylic plinths, and combinations of plinth materials.
The reason why maple may be used for instruments like violins could be because it resonates well, in which case it may not necessarily be the best material for a hi-fi rack. My expertise isn’t music, but I have a brother who plays the violin in an orchestra, as well as collecting and repairing them, so I’ll ask him when I see him at Christmas, if I remember. In fact, I did a quick search on violin making, and the first one I came to,
http://www.centrum.is/hansi/construction.html , mentioned that the front and back of the violin have to be very thin, and resonate very well! So I certainly wouldn’t pay too much attention to what the chap from Mapleshaderecords says. It sounds as if he likes the colouration that resonating woods like maple introduce. His rubbish about how if you don’t have his miraculous speaker cables, your $2000 speakers can sound like $100 ones is just that – rubbish which is designed to part wealthy, gullible people from their money. They may very well make your speakers sound better, but the difference wouldn’t be equivalent to spending $1900 more on your speakers, as he seems to imply! No doubt if he gave the cables to a hi-fi reviewer and promised to advertise with them, they’d say how much different they make speakers sound, but then they’re hardly impartial, are they? He also says that long speaker cables are better than short ones. Obviously the electrical engineering that I was taught about making wires as short as possible to minimise resistance was wrong! And directional wires?? Obviously they wouldn’t be any good at passing AC signals then – maybe they’re for DC power supplies? Don’t waste your time looking at his site. It looks to me as though he’s got little in the way of engineering knowledge, so he resorts to making things up to try and sound knowledgeable. His website is a combination of truths, half-truths, sheer rubbish, and advertising. Sometimes all in the one sentence! It would be funny if it wasn’t so misleading to hi-fi buffs who have little engineering knowledge.
Alright, I’ve had my rant and I feel better – now back to practicalities. Many hi-fi rack manufacturers isolate their racks by sitting the shelves on vibration isolating pads, such as rubber, foam or other materials. It helps to also have a relatively non-resonant material to make it out of – many make them out of glass, which resonates at a quite high frequency, or out of MDF, which is less resonant than most natural wood. That’s why virtually all speaker manufacturers make speakers out of MDF or similar materials. The MDF is less resonant because it is wood that’s been broken up into very small woodchips, then glued and compressed back together, rather than having a nice naturally resonant grain running through it, like maple, oak, eucalypt or any other tree wood! Whether it makes much difference to an amplifier is debatable, but under an electro-mechanical turntable, non-resonant and de-coupled from the environment is best. Resting your turntable on bubble wrap is probably good, if it’s several layers of bubble wrap. Using two bicycle tubes, inflated to a very low pressure, under a shelf resting on them, is another idea I’ve heard, and there is a commercial anti-vibration shelf using that idea being marketed, although it’d be cheaper to make your own.
And dnsey, the reason why many people prefer open racks rather than closed racks is probably to provide good cooling for electronic equipment, particularly high power amps, which get hot when working hard. It may make sense to keep sound waves away from things like turntables, but most electronic equipment is more reliable if it's kept relatively cool.
Build your own stereo rack!
