I look forward to that write up when you have the time.
Having been an architect for close on 40 years I have had many projects which required mechanical and acoustic isolation such as apartments directly above nightclubs. In all of these the absolute no no was direct metal on metal contact and the best was no physical contact at all or if not that then the use of carefully controlled materials such as silicone, rubber, foams or springs.
If I was to consider isolating my Dave or Blu2 I would possibly start by suspending them from suitable springs rather than using metal bowls or ball bearings and hence why I would be very interested in your experiences.
OK Nick, here it is (time to get this off my to do list).
The finding was an extreme surprise to me. I was expecting at best a very modest improvement, but it turned out to be one of the biggest positive impacts I had had on my system (esp. when applied to my DAVE). That's what led to the trip down the rabbit hole to figure out what the heck was going on.
As background, way back in the day I did a lot of laser interferometry and microscopy, ultra small device characterization (pico amps), and a detour into patch clamp work (measuring the electrical signal from ion flow from individual proteins opening and closing). I have a lot of scar tissue from phase-related phenomena and mechanically induced electrical noise (as in, spend 18 months getting measurements clean enough so you can measure the damn device and finally graduate scar tissue). Although orders of magnitude less extreme, the timing precision and phase coherence of Rob's DACs tickles a lot of those intuition centers. The music just feels more real as things get more phase coherent. Insane that the brain can process differences at this level, and that perception is altered so much as a result of seemingly small changes.
When I first got my DAVE, I followed Roy's well trodden path and got an Acoustic Revive TB-38H and Black Ravioli pads under my DAVE. The Acoustic Revive has some ground up quartz (it looks like) to dissipate and absorb vibrations, and best as I can tell the Black Ravioli pads are some sort of visco-elastic material. Definitely had a welcome audible impact, but at the level of "hey, something seems wrong" if you took it away, not at a "what the hell is going on?" level of impact if you took it away.
Both of these components basically absorb vibration (which is good) but it was an open question for me whether they could isolate against vibrations in the audio range of frequencies (20-20kHz). In doing some research, I found a lot of approaches to mechanical isolation, but I was intrigued by the roller ball technique that Barry Diament championed:
http://www.barrydiamentaudio.com/vibration.htm I've heard a lot of Barry's recordings, and I trust his ear. This is worth looking at.
Basically, the idea is to fabricate a bowl of hardened aluminum, and float whatever you want to isolate on precision ball bearings on these bowls. The better polished the bowl and more precisely spherical the ball bearing and the harder the materials (to have less deformation), the more easily the object your isolating could float horizontally in the bowls. It looked interesting to me because of the presumably near ideal horizontal isolation, but at the trade off of strong vertical coupling (metal to metal). I briefly considered suspended springs and a heavy platform, but my living room isn't ready for that kind of experiment yet
I found a commercial source that took Barry's concepts and sold these bowls with a generous return policy (
http://www.ingress-engineering.ca/products-and-services.php). I'm always appreciative of vendors that allow in home auditions, so I ordered a couple sets of the Level 3 rollers to give a try. You can also take 3 shallow ceramic bowls and some glass marbles and get a crude sense for what the technique can offer. If you hear anything, take that next step for more precision materials.
When I got them, I put a set of 3 under DAVE and fired it up. I couldn't believe what I was hearing: 3D'ness and detail in sound stage was off the charts. With binaural recordings, I had a true forward/back/up/down immersive experience. For recordings in large spaces (churches, etc) the feeling of being there was incredible. This had gone from a throw away curiosity to something that needed a lot of attention.
My next step was to get a polished 12x6" ceramic tile from Home Depot. I put this polished side down on the 3 roller balls, and the DAVE on top of that. This took the effect next level still (the underside of the DAVE is rough, so the polished tile floats better on the roller balls).
Basically, I found the following: take the platform on the roller balls and starting it oscillating back and forth. Measure the time it takes for it to stop oscillating. The longer that time, the more freely the platform was floating, and the more amazing the sound scape I was hearing. During my experiments (everything from bowl diameter to ball bearing diameter to ball bearing spherical precision to polishing techniques to ball bearing material hardness), I managed to get from ~30 seconds to ~90 seconds. The correlation to better imagine and holographic feel was spot on: the freer the platform was to go back and forth, the better and more real things sounded.
I have a machinist friend, so I had him machine out bowls with various bowl indentation diameters (IIRC, Barry originally had 2" diameter bowls, and Ingress has 3" diameter indentations in the bowls). The flatter the bowl, the lower the native resonance frequency of the bowl is, and the freer the motion. Too shallow and things would just roll out of the bowl (not good). I ended up with 4" and 5" diameter indentations in the bowls.
The hardness of the ball bearings made a difference (tungsten carbide vs chrome steel, etc), but a bigger impact was the spherical precision of the bearings (grade 25 chrome steel sounds better to me than grade 10 tungsten carbide). However, by far the biggest impact was the polish I was able to get in the bowl itself. Can one hear the difference between bowls polished in different ways? Crazy, but most definitely yes (again, very strong correlation to how long the platform would oscillate back and forth...better polish and higher precision bearings == longer oscillation).
So today I have my DAVE on the following: Acoustic Revive base (sounds worse not to have it...still need some vertical isolation), three 5" diameter bowls forming the biggest triangle I can, GS25 chrome steel bearings, 12x6" polished ceramic plate, DAVE. I experimented with having the Black Ravioli pads in the mix, but it gave up too much surround spatial imaging to have them there.
Since I had a lot of these things lying around after all my experiments, I also have the roller balls under power supplies and all my electronics. The impact diminishes the farther I get from my DAC, but it is still there (DAVE is the biggest impact by far). Basically, the closer something is electrically to the DAC, the more of an impact it is having.
For giggles (and because Barry swears by it), I also put these under my speakers (!). That was a much more challenging thing to do mechanically. In the end, I took the weight of the speakers, found sorbothane pads that are spec'ed for that weight (the material needs to be at an optimal pressure to be maximally vibration absorbing), and got a large marble tile to put on top of the sorbothane pads (one pad at each corner of the tile). This is the base for my speaker. I then used double back sticky tape to tape three 5" indentation diameter bowls to the underside of the speakers (as big a triangle as I could make), and placed the speaker on three 4" indentation diameter bowls with a precision ball bearing between them.
Very very strange to touch a speaker and have it rocking back and forth, but the sandwich configuration it is quite safe (you can give them a big shove, they rock back and forth, but don't come out of the bowls). The ingress engineering guy also has some screw in speaker feet that use a similar configuration.
A bonus of having the speakers on these roller ball bases is that it makes fine positioning of speaker much easier. Anyone can use this technique to phase align their speakers, but it is 10x easier to do when you have the speakers on roller balls.
Here is my bonus trick for those of you that are trying to get hyper precise imaging and sound stage out of your 2 channel systems:
Level your speakers as best you can, and do your best to have toe in identical and the distance from the driver to your listening position as close to identical as you can (I did this by measuring to ~1mm the back corner of each speaker to the wall behind the speaker) Find a mono pink noise FLAC on the internet and play it back through your system on a loop. Have a buddy tweak one speaker until things pop into a crisp dot (move your head around...if your speakers are close to aligned, you'll hear it). Keep having a friend adjust the speaker until that dot is right in front of you. The crisper and tighter the dot, the more phase aligned your speakers (as an aside, great trick when you're tracking down reflections in your room...get rid of room reflections and the dot will snap in tighter and tighter).
Once you have it the best you can possibly get it, flip the phase on one of the speakers (swap the red and black inputs to the speaker). The dot will now be a null spot where the sound from each speaker is canceling out the other. Keep doing tweaks to maximize that null (including any room treatments you're doing). The more perfect the cancelation of the out of phase mono pink noise, the more perfect the phase alignment of your speakers (and if you have single driver high efficiency speakers like the Omega Super Alnico Monitors or Voxativ's, you can get basically perfect phase alignment). When all is done, go back to the correct wiring on your speaker, pop in a favorite track, and hear a sound stage you've never even dreamed of on your system.
Above pink noise speaker placement trick works for everyone of course (and I recommend it to everyone), but with the roller balls under the speakers, it is incredibly easy to get the speaker position dialed in perfectly with your finger tips: move the speaker until the dot/null is where it needs to be, then adjust the bowls so the speaker naturally rests in that spot. Do that a couple times, and it will be dialed in perfectly.
Anyway, very very easy to try this sort of thing in your system: get a $5 polished ceramic tile from Home Depot, get some of the level 3 Ingress roller bowls ($150, fully refundable) and give it a try, or find 3 polished shallow ceramic bowls and some glass marbles ($10, not refundable) and give it a try. If you like what you hear, there is more to be had, but that is a low risk way to see if the effort is worthwhile for you and your setup. If you decide to go nuts, drop a PM and we can compare polishing tips and tricks
For those that made it this far, if you're appreciating how amazing DAVE is, you're indirectly poking at the question of how the heck can our brains tell what is happening at -120dB to -300dB? That's madness! But it is also what Rob is measuring and what we're all hearing when we hear the amazing depth that you get from DAVE.
When you back out from that, it takes very very little to induce noise in that range. Should you be able to perceive it? All rational presumptions would say "of course not!". However, the timing precision of Rob's designs has some psycho acoustic magic that dissipates when things at this level get introduced.
Back when I first started to get my head around the impossibility of what I was clearly hearing, I found this post by Rob very provocative, and it certainly opened my mind to the possibility that these seemingly trivial changes could have SQ impact:
https://www.head-fi.org/threads/chord-electronics-dave.766517/page-306#post-12845536
