Based on some debate going on in the forums about various vibration-control approaches, I decided to buy a set of four Solid-Tech Discs of Silence and publish this review. I hope that you find it helpful.
Here is link to the Solid-Tech website: http://www.solid-tech.net/products/discs-of-silence-4537455
1) Here is the order of the "stack":
Target rack spiked to slab foundation => MDF shelf with Dynamat on both sides => DofS => Symposium Svelte shelf => SR Mig 2.0s in Precision Imaging configuration => Sony 5400ES
2) DofS= Discs of Silence.
3) Listening source was SACD and Redbook CD via a Sony SCD-XA5400ES SACD/CD player.
4) The evaluation system can be seen on my "Virtual System" page.
5) Both REL Stadium III subwoofers were left off during the entirely of the evaluation session.
The DofS came configured with three springs per footer and a simple spec for installation: "When correctly loaded the operating height is 32-35mm". In order to achieve this required height with the weight load under evaluation (Sony XA5400ES, Symposium Svelte 19" X 14" platform, (3) SR MiG 2.0 footers, TTW 1080g brass weight on top of player), I removed one spring on each footer, leaving two. Resulting height was within spec on all four footers. Shelf underneath the DofS/MiG/Sony stack was verified level prior to assembling "stack". It was easy (automatic) to achieve true level with the spring footers in place.
When giving the player a gentle but firm nudge, it wobbles in a controlled fashion for around 5 seconds before settling. Changing of discs does not create any significant visual wobble. All motion appears to dissipate while the Sony initializes reading of the disc and well before it begins to play.
Perceptions of my system’s sound BEFORE installation of DofS:
1) The sound of sudden dynamic transients was razor sharp in the upper-mids/treble and good but slightly vague in the lower-mid bass and especially in the extreme low bass. The image definition of acoustic bass in its lower registers was not in synch with the rest of the frequency spectrum. There was a slight hyper-edginess to the sound of acoustic strings and cymbals that disguised itself as openness and superior detail retrieval. Female vocals were clear and articulate but somewhat tinged with a "silvery" quality while male vocals were also clear but a touch too chesty(especially those of male performer’s with low, throaty voices) and sounded more diffuse than in real life.
2) There was a pleasing-to-me-in-an-audiophile-sounding-way blackness between instruments and performers. The same was true of the transition between the midrange and low-bass frequencies. The mid-bass was there but harmonically reticent in relation to the overall sound. This had the effect of creating a refined harmonic separation between the low-bass and mids/upper frequencies. I have heard this before in many systems and think that many audiophiles prefer this sound characteristic.
3) On source material with massive content of dynamic low-frequency acoustic bass notes or a well-recorded and very-dynamic piano, severe distortions indicative of amplifier clipping occurred infrequently but were consistent and repeatable when listening to the same track at the same volume. The single Classe’ Audio DR-9 (conservatively rated at 100w/ch and doubling down as impedance halves) was being overdriven with the Thiel CS-5i speakers’ load. On occasion, limiting the volume to eliminate the clipping precluded listening at venue-correct volume. This was very disruptive to enjoyment of the musical performance. This is the first time I can recall experiencing this with an amp in my system, having used the more powerful Classe’ DR-25 first and then later the Krell FPB-600c before the DR-9.
Even later in time than the change of amplifiers, I replaced and restructured the rack supporting my Ayre CX-7eMP Redbook CD player and this is when I began hearing these severe distortions. Replacing the Ayre with the Sony, due to the latter’s more dynamic presentation at the frequency extremes, exaggerated the problem further. More about this later.
Listening impressions AFTER inserting the DofS into the system:
1) The razor-sharpness of sudden dynamic transients in the upper-mids and treble is stunted just the slightest amount. This is very apparent on xylophone where the ringing of the mallet strikes is now less pronounced. The hyper-edginess in the sound of acoustic strings and cymbals is gone. The vagueness in the mid-bass and the extreme low-bass is largely eliminated. I am still not ultimately satisfied with the extreme low-bass definition but it is MUCH better. Mid-bass definition is very close to perfect now to my ears. The "silvery-ness" of female vocals is gone as is the chestiness of certain male vocals. The perceived airiness of the sound is slightly reduced as well, being replaced by a more natural, authentic sense of openness and air.
2) The cohesion of the sound between the mids and the extreme low-bass is much improved. Some of the "blackness" between instruments and performers has been replaced by rich harmonic overtones in the lower-mid/mid-bass region. I did not like this at first, but further listening with evaluation material that I am intimately familiar with has moved me to decide that this is more-musically accurate. Image definition is still as good as before, perhaps even better, but there is now a rightness to the mid-range region that was missing previously. I am trying very hard to avoid over-used audiophile adjectives in this writing (I hope it shows), but I just have to say that PRaT is much improved with the DofS in the system due to the lively reproduction of lower-mid/mid bass harmonics. There, I said it. Have mercy on my soul.
3) Regarding the severe distortions articulated above in the pre-DofS system, they have largely disappeared, at least at venue-correct volume. The distortion heard on piano is now completely gone and the low-bass distortion can only be heard on the most dynamic acoustic bass tracks. I postulate that the sonic effects of vibrations entering the Sony 5400ES pre-DofS were causing the DR-9 amplifier to clip in the regions of utmost-prominence, in effect overdriving the amp by amplifying the distortion from upstream, much like what happens when woofers pump due to poor vibration control/setup of a turntable. In retrospect, I am certain that these severe distortion heard from the loudspeakers was caused by the poor vibration control characteristics of the "new" rack arrangement underneath my CDP and that the extremely positive effects of the DofS in this situation might be less pronounced with a top-class rack/support accruement in other systems.
I did not notice any detrimental effect on any other attribute or criteria of the sound of my system with the DofS in place. No "darkening of the soundstage". I am certain that with more time to listen to even more diverse musical selections, I will notice more differences, positive and possibly negative ones.
Best to all,