LS50 and Big Fat Dots

For an interesting take on component isolation (including speaker supports), go to the Barry Diament Audio site, under "Articles", then "Vibration control for better performance". Barry is a proponent of the "roller bearing" theory.

Exactly Geoffkait. In Barry's writings he describes the roller bearing as an isolator in the horizontal/lateral plane, and a coupler in the vertical. He makes the argument that most vibration travels horizontally, the waves moving across the floor, just as the movement of the ground in an Earthquake is horizontal/lateral. He recommends an air bearing for vertical isolation, something as cheap as an under-inflated bike tire inner tube under a piece of plywood up to the old Townshend Seismic Sink. Townshend himself now sells a spring isolator (the Seismic Pod) which he claims isolates in both planes.

TVfreak, the problem with the dots (as well as Sorbothane, etc.) is their rather high resonant frequency (see the technical info on Townshend Audio's site, where graphs of the resonant frequencies of Sorbothane, spikes, and Townshend's Seismic Pods are shown). It is not down where it should be, in the low single digit frequencies, but rather high enough that it causes resonance in the audible frequencies, leading to the well-known bass bloat heard with rubbery isolators. Spikes don't isolate at all at very low frequencies, being very efficient couplers below a certain frequency. The theory of a spike being a mechanical diode (allowing vibrations from the speaker enclosure to travel down the spike, but not vibrations to travel up it) has been proven to be untrue.

If you want to try roller bearing isolation, you can make a set on the cheap (see Barry Diament Audio for details), or pick up a set of three from Ingress Audio Engineering for $75 plus shipping. If you do make your own, and want the lowest resonant frequency possible, make the surface the ball bearing rolls across flat, rather than bowl shaped. The surface the bearing sits on will need to be perfectly level to prevent the speaker from being able to roll off the bearing---you may want to add a ridge around the flat plate! That's fine in theory, but not a very good idea in practice. If the bowl has shallow enough "walls" (Barry suggests the bowl be formed to the profile of a 2" diameter sphere), it's resonant frequency will be in the very low single digit range, providing excellent horizontal/lateral isolation (but coupling in the vertical plane) for any loudspeaker, or even subwoofer. With a slight bowl-shape, the ball bearing the speaker enclosure sits on will still be able to move horizontally/laterally (contrary to what you may have read in a previous mistaken posting), it will just have to "work" at climbing the incline of the bowl's wall, which it is obviously free to do. That merely raises the resonant frequency of the roller bearing slightly, which will none-the-less still be very low, much lower than the dots. A set of three DIY roller bearings good enough to test their theory for yourself will cost you only five bucks or so.

Max Townshend has a 25 minute video on You Tube discussing the topic of vibration and it's effect on hi-fi (he has done a lot of research on the subject, and is considered an authority in the field). In it he covers spikes, and states as fact that they are just as efficient at transmitting vibration up them as down. The video is definitely worth 25 minutes of your life.

Max makes a great isolation product, the Seismic Pod. Unfortunately, it costs about $200 for one, and you need a minimum of three for any item placed on them. A set of six (three per speaker) will cost you almost as much as the LS-50's, eight more than the speakers!

Nonoise, the Ingress Audio Rollerblocks come in sets of three, each having a top and bottom cup. The provided 3/8" ball bearing is placed in the bottom cup, the top cup is placed on the ball, and the component on top of that, just as Symposium Acoustics RollerBlock Jr's. Using both cups makes for a slightly higher resonant frequency and more damping that using just the bottom cup (as with the Symposium original model). Barry recommends using only the bottom cup, with a hard smooth surfaced object (a stainless steel disc, for instance) on the bottom of the component, for the ball bearing to roll against. You are free to try them both ways, of course.

Ingress also offers a newer model Rollerblock, made from harder 7075 aluminum, and with a larger, shallower bowl, the bowl being machined as part of a 2" diameter sphere. The less steep walls of the bowl provides a lower resonant frequency and less damping (the ball rolls for a longer period of time) than the original model, and this model is sold in sets of three, intended to be used on the bottom only. The ball bearings are the same 3/8" diameter, and the set of three is $90 plus shipping. The aluminum of the bowl of the 7075 model is also more highly polished than that of 6061 aluminum original model, for less friction. The 7075 model provides more isolation than either of Symposium's models (as well as the Ingress 6061), a result of the bowl's dimensions.

Isolation in the vertical plane, if desired, needs to be dealt with separately. The cheap DIY method is an under-inflated inner tube on a piece of plywood, which works as well as any commercial product, including Townshend's original Seismic Sink, which was not cheap (and is no longer available new). You can even put a piece of ply across the front of the platform, to hide the inner tube, paint the whole thing black, and have the best isolation known to man, for only a few bucks.

Probably the most important consideration in locating the speakers is to have them right at the front edge of your credenza, so that you don't get a reflection off it's top surface. The isolation devices will help the speakers "disappear", the speaker enclosures being less of a sound source.