Loudspeaker-Floor Interface
Posted by: CharlieP on 15 November 2015
I started this thread because I received a phone message from a forum member asking about the bases under my speakers. Unfortunately, I could not quite make out the correct phone number nor do I know his forum name. Hopefully this may address his questions. Having said that, it would be fine if a discussion ensues.
Here is my current configuration, which is providing me the best music replay I have yet enjoyed. This is not to say that it could not be improved!
There is wool carpet on the oak hardwood, under which is a suspended wood-framed floor, under which is a crawl-space. 16" square by 2" thick concrete slabs (gray) sit on the carpet. The speakers have three pointed cone feet, which I think are brass. The cones sit in Fraim Chips. Under each frame chip are three 3/16" diameter ball bearings. Because of the textured upper surface of the concrete, the balls do not roll.
Until last spring, these speakers sat for many years with their spikes through the carpet into the hardwood, which left small dimples. My system was in storage through summer, and the hardwood floors were refinished. For two months the carpet remained in storage and the speakers sat on the new Fraim Chips, as a necessity to avoid dimples in the newly-finished oak flooring. I cannot comment on the sonic difference contributed by the Chips, compared to no Chips, because several months ensued and my shelving was rebuilt with closer attention to cable dressing. When the carpet was finally returned, two months ago, I faced the challenge of whether to trim the carpet shorter, or do something else? Really, just as an experiment, I procured these concrete slabs. Similar arrangements have been reported as effective by several forum members.
Initially I placed the speaker's cones directly onto the concrete upper surface. Letting this configuration "settle in" a few days, I felt with considerable relief that it sounded better than when the chips sat directly on the oak flooring absent the carpet. The points tended to "dig in" a bit to the concrete, making a bit of grit. (Each speaker weighs about 100 lb). This made me a bit concerned (for the sound, not the concrete), and I had these Chips sitting there, so I tried putting the chips under the points. Again listening for a few days I felt the Chips a worthwhile addition, confirmed when removed. The effect of the Chips was not profound, but the improvement was there. A similar concern led me to try the balls under the chips - in an attempt to further linearize the interface. Again, I felt there was an improvement, if perhaps subtle. I have not yet tried to remove the little ball bearings - they are "swearing nuisance" to fit, with my wife's patient assistance.
My motivation is to have the best possible natural sound. In service of this, I try to minimize within reason the vibration of the speaker itself and the floor. Further, it is essential that what vibration remains (there will always be some, however small) must be highly linear - free of micro-rattle and hysteresis.
I have to say that my music has never sounded so wonderful - due principally to other improvements I have made - which makes me disinclined to experiment further. But I am open to persuasion if there is a better way.
Charlie
It is a fascinating write up and echoes some things I have seen in the past with some more exotic attempts. The most extreme of which was concrete blocks loaded down deep into the earth several metres surrounded by another concrete containment filled with water creating a moat. The central concrete bore rising up through a hole cut in the wood floor to be flush with the surrounding floor itself with the speakers resting on that. I cannot imagine anyone going to that extreme (even when building a new home) but someone's done it.
Back down to earth, I found a good compromise between concrete plinths (which I cannot use for a number of reasons) and smaller spike shoes are these items from Kripton:
I have yet to use a better spike shoe.
There is a caveat. The silicone ring on the underside doesn't bear any load but it does make them immobile when the slighted pressure is applied. I find starting with Linn Skeet helps because they slide easily over wood floors without scratching so you can get the position just so. Then swap them out one-by-one for the Kirptons once the positioning is set. They have a range of sizes and masses going from low cost to silly money (starting at about 50 quid for 4 going to around 200 quid).
I thought about using Krypton, but the flow rates necessary to support speakers on a jet of gas made it infeasibly expensive (and noisy). 
It is a fascinating write up and echoes some things I have seen in the past with some more exotic attempts. The most extreme of which was concrete blocks loaded down deep into the earth several metres surrounded by another concrete containment filled with water creating a moat. The central concrete bore rising up through a hole cut in the wood floor to be flush with the surrounding floor itself with the speakers resting on that. I cannot imagine anyone going to that extreme (even when building a new home) but someone's done it.
Back down to earth, I found a good compromise between concrete plinths (which I cannot use for a number of reasons) and smaller spike shoes are these items from Kripton:
I have yet to use a better spike shoe.
There is a caveat. The silicone ring on the underside doesn't bear any load but it does make them immobile when the slighted pressure is applied. I find starting with Linn Skeet helps because they slide easily over wood floors without scratching so you can get the position just so. Then swap them out one-by-one for the Kirptons once the positioning is set. They have a range of sizes and masses going from low cost to silly money (starting at about 50 quid for 4 going to around 200 quid).
feeling_zen, have you compared the Kriptons to Naim Chips?
No. I never made as far as Chips.
For me, the thin silicone ring inset on the underside of the Kriptons was a major point because it makes them truly laterally immobile with even the slightest pressure (you can find a thread from when I used Skeet and my wife pushed the speakers with the hoover). The load is borne entirely by the high carbon steel of the pucks and the silicon provides just enough contact grip to hold them in place.
The PMC FAQ with the mention of bluetak got me thinking. For those of you with stand mounts and/or granite slabs, silicone earthquake pads might be worth a try. They cost next to nothing, I guess between $5 and $10 for a pack, come in many pre-cut sizes and even the small ones can take a load of around 100Kgs. Either between speaker and stands or granite slab and wooden floor. You can have them down for years and they never pull the varnish up when removed. The PMC article mentions spikes or bluetak as being ideal which is a little strange as they do different things. Spikes dampen by decoupling contact area and bluetak by absorbance. If going the absorbance route, these pads might be the ticket, especially sandwiched between floor and granite or pairs of granite slabs. They are specifically designed to provide enough compression and stretch to hold heavy items in a magnitude 7 quake by letting the supporting load move about.
Interesting reading folks but would be way more informative with some pictures.... 