Originally Posted by sjt78
How does the material of the shelf affect the sound? I can see if I were putting speakers on thin glass shelves how they would vibrate and not sound good, but for components? I'm not sure I believe that. How about 1" thick glass, would that sound different than 1" MDF or 1" hard wood? Not that I'm saying I wouldn't like thicker glass shelves to come with the Target audio rack, but I'm not convinced it is degrading the sound.
This is really a huge topic, admittedly controversial. My approach is this. Once again, the effects will be much more important in speaker systems due to speaker-induced vibrations and room vibrations.
Various gear will have varying susceptibility to vibrations and resonance. Gear with less moving parts, more robust enclosure/construction will be affected less. CDP in general will be most affected, especially if using the typical cheap, flimsy sheet-metal most cheap gear uses. Clocks and digital chips widely in use today are very susceptible to vibrations. A room that is constructed from wood/plaster will be more affected than concrete rooms.
A given gear, let's say a CDP, is under attack from 4 sources of vibration/resonance:
1) Floor-born vibration--speaker/room vibration will be transmitted to the gear straight through the audio rack. This is probably the main reason better racks like Lack make the most difference. Some believe the very low frequency resonance from the earth itself affect sensitive gear. Denser material such as steel is not necessarily better b/c they tend to better transmit the floor vibration to the gear (bad). Something like Lack, by virtue of its multi-layer low-energy-storing design, dissipates more of the floor vibration before it hits the gear.
2) Air-born vibration--the more air speaker can move, the worse this affect. When air-born vibrations hits the CDP, that vibrational/resonance energy will both stay in the CDP and dissipate through its feet to the shelf/rack. The more energy that stays in the CDP and affects the delicate chips, transport mechanism, etc, the worse the affect. Designs such as Lack increases the portion of energy that's dissipated through the shelf/rack (good). A MDF shelf or glass tends to receive the energy, but they are not as good as dissipating that energy away. Instead, MDF/glass can even spit back the vibration energy into the gear it's sitting on.
3) Cable-born vibration--those stiff audiophile interconnects, speaker cables, power cords can transmit vibration from speakers/air/room right back into the gear. It is my belief this is part of the reason why the external jacket of cable alone can make some difference in sound by their damping properties, both for electrical signal going towards speakers and mechanical vibration coming back to the gear.
4) Internal vibration--in the case of CDP, the rapid motor mechanism, vibration of the CD/transport generate self-vibration that has to stay inside the CDP or be dissipated outside. Even gear without "moving parts" actually do have a lot of low-level and/or microscopic vibrations. All those transformers all have varying amounts of vibrations as well as low-level 60Hz hum that permeates everything. Various strategies to drain away these self-vibrations, including Lack, will be important especially in headphone systems, where the bigger speaker-affects are absent, unmasking the problems that are usually masked by speaker/room vibrations.
That is how I digest the various theories I've read about or experienced by trying various strategies. And I'm sticking by it