I realize you didn’t ask me but I’m bored waiting for UPS so here goes. I always opt for near the most rigid halves or quadrants of the chassis for primary isolation. When using 4 devices its at 4 corners. When using 3, which I frequently do for lighter components I’ll use two at the heavier front-to-rear end then a third centered in the opposite end with a similar inset to the other two. One thing you can never accomplish successfully is using more than 4 as it requires using 3 or more in parallel in at least one axis. In that event one device ALWAYS gets a free ride! If its a thin metal floorpan like the DS I’ll try things centered under it like a rubber ball, half a rubber ball, a firmly compressed foam plug or appropriately sized sorbothane bumper. A cone shaped urethane bumper that’s .875" (7/8") tall with a self-adhesive .750" diameter base is hands-down my all-time favorite center isolator (snub damper)! Any compliant, compressible polymer with a low-med Shore A Durometer hardness and good memory, doesn’t take a set at moderate compression and will offer consistent and repeatable damping between component “rattle pan” and whatever its sitting atop. Done right its has no adverse affect on primary isolation but subdues internal chassis resonances allowing the primary isolation method to focus on what they do best while simultaneously working less hard by allowing them to work within a narrower frequency range of NVH.
Manoet said Done right its has no adverse affect on primary isolation but subdues internal chassis resonances allowing the primary isolation method to focus on what they do best while simultaneously working less hard by allowing them to work within a narrower frequency range of NVH.I'm happy you're bored Manoet! This idea seems to resonate (no pun intended) I have never experimented with rubber balls or foam or sorbothane-you may have posted pics of these tweaks before but I'd love to see what you've done...
(edit-shrunk my very grotesquely large emoji)
Here’s a pic of my favorite snub mount used at the center cross-section of a thin component floor. These are a few “thou” over 7/8" inch tall but can be shimmed on their underside or have a small shim. coin etc adhered directly over the cone to achieve an ideal compression length once component height is achieved. I prefer to use them oriented point down but admit that may well be much adieu about nothing. I’ve tried using them singly or in triplets/quadruplets but solo compressed about .080-.100" when in place seems preferable to multiple cones compressed a lesser amount. Heavier components might like more cones or a little more compression and lighter a bit less. There’s no hard & fast rule with these but a pleasant weekend morning experimenting can reap dramatic rewards. These don’t respond well to sliding components but prefer a little lift-&-scoot to keep from toppling them when attached which you’d likely do anyway to prevent scuffing/scratching with your primary isolation components.
Additionally I prefer my primary isolation threaded rather than just lying there. On a 3-piece design its less important but on a 4-piece its crucial as almost no chassis is ever perfectly flat! Just move your devices around individually by hand… there’s always one that slides easier than the other three. Shim it and and now one of the others is outta whack! In actuality all four have dissimilar friction coefficients to the surface they rest on to a greater/lesser degree. With threads you can compensate more exactly and quickly by starting with them screwed in till contact is just made then threading each one individually downwards until a similar/identical resistance is felt in the thread resistance. Without threads you’re at the mercy of metal/foil shims for metal components and parchment or similar for wood/MDF components. An altogether fiddly, cumbersome and unexact science comparatively speaking.
I buy these conical snub mounts from a machine tools supplier I deal with but wouldn’t surprise me to find them at Amazon or a myriad of other places tho direct might have unrealistic minimum orders for the likes of audiophile end-users. They’re wonderfully inexpensive, work like a dream and ostensibly seem to last forever. I haven’t killed one yet! Oh and since I’m going over to iPhoto to retrieve a pic I’ll also snag the ones I took when I did my DS isolation and SR Red fuse conversion.
Nice work! So are you using a single bumper combined with the Rollerblocks?
Initially I tried without the snub and added it a day or two later. LOTS better! Then 5 weeks after buying the DS new, I purchased a new Devialet 200. Now the DS is for sale with the modifications since they cannot be transferred to the Devialet. The life-long story of an OC audiophile… “buy retail, sell wholesale!”
I have given the FIM Platinum isobearings a go on several components but did not have great success. I’ll have to give them a try combined with an absorptive device. On the advice of something that I had read on Steve Hoffman’s website I used only the cup underneath and had the bearing directly contacting the base of the device above. A smoother interface was recommended but I hadn’t gotten to that yet. It looks like I should give this a more serious run through and follow the advice better.
I definitely hadn’t counted them out, just put aside till I had time.
In noodling around on the Google, I found a product called “Moongel” (yes, I am serious, Moongel) that is used to dampen pesky resonances in drum heads. The drone-camera crowd is using these to dampen vibration that affects video camera operation. These wavelengths are proooooobably(?) in the audio range and their results are interesting when comparing several dampening materials. So, it turns out, Moongel is related to (or actually is) the sticky blend of polymers and adhesives that make up the “stick to anything” toys that my sons put everywhere when they were little.
Skip throughout all three of these for the meat. They are rather lengthy.
https://www.youtube.com/watch?v=5mFbmjGpp9M
https://www.youtube.com/watch?v=TMcUXRPpTJ4
https://www.youtube.com/watch?v=h3y4Clyf1cw
Here is something that I found handy.
http://www.paramountind.com/pdfs/paramount_durometer_scale_guide.pdf
S’funny you mentioning drum skin resonances. Years ago when the concept of thin floorpans dawned on me, drums were the first comparison that came to mind. The way light reflects off the 2nd surface of a bass drum when when the inner skin is struck. How that skin with the bands name or logo ripples & pulses from the center outwards like a pebble in a calm pond only with dramatically higher surface tension than water. That mental image told me where to dampen, ie; where the most movement is. I would suspect Moongel (keep wanting to call it moongoo) could work quite well and if cheap enough certainly worth a shot. Two concerns I’d want to explore; first that it works over a wider frequency than the single hover speed of a quadcopter and secondly that it doesn’t break down and harden or dry out due to chassis heat in a confined location. Easy enough to replace the top layer or two if necessary. If it occurs regularly a yearly or biannual solstice/equinox replacement kinda thing.
Interestingly Deflex panels designed to be adhered to the inside rear panels of speaker cabinets, opposite the woofer to absorb standing waves are an eerily similar material & consistency to Moongel. Cast with a smooth, flat rear surface for easy adhesion to cabinet but front is cast with small-to-large annular rings emanating from center of sheet outwards. Its maybe 3-4 X thicker than Moongel but of a very similar soft/flacid Shore durometer.
Or we could just lick gummy bear feet and plant em centered to the floorpan 
Doing both. Have a large HRS damping plate on top and Mapleshade Triple Points as footers. Don’t really know if the damping plate has much, in any, affect but figure it doesn’t hurt. I’d been using BDR #4 cones and pucks previously which I preferred over the stock feet. The Triple Points have a little more top end extension and a nicely centered sound stage although they have a little less bass impact compared to the BDR.
I have had good success with various products from Herbie’s Audio Lab. Most of his stuff is inexpensive and you can return things that don’t work in your system. I am using his Tall Tenderfeet under my DS (I have not yet taken time to compare other footers–maybe someday I can afford to try the Stillpoints). One of the biggest surprises of my audio life came when I put Herbie’s “Thin Dots” between the aluminum cones and the shelves that they support in my Solidsteel rack. This really cleaned up the sound. Please don’t ask me to explain this but there was no doubt about what I heard.
A ‘good’ rack/shelf is paramount. When I first got into hi-end audio I was using crappy, cheap racks. I got a couple of Michael Green Room Tune Justa Racks. The difference was outstanding & relatively cheap. I would like to get the Isis rack by Symposium Acoustics but I cant afford it.
Under my DS I use (probably impossible to get) Yamamura Churchill SP-0. This is a three point system that, kind of, lets the component “float” back and forward and side to side. It improves the sound but not as much as the racks did.