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Anti-vibration spike interfaces

The seventh instalment of the vibration control epic odyssey
[Point Disc Underfoot]
Point Discs Underfoot
[Italian version]

Product: Polycrystal PD-1 Point Discs
Supplier: UltraSystems
Approximate cost: $2.95 each, yes, really!
Reviewer: Mark Wheeler - TNT UK
Reviewed: June, 2005

The Polycrystal PD-1 Point Discs are a rare product. I know of only 3 similar attempts at commercially produced spike-interfaces. One of those ceased production years ago, the Origin Live machined steel cups supplied with their excellent but no longer made speaker stands; they were a 6mm thick steel disc with a cup machined onto one side, designed to be attached to speakers using a thin smear of Blu-Tac. Clearlight manufacture RDC Cone Cups, ostensibly for use with their own RDC Cones but equally adaptable for use with other spikes; I did try to get hold of some of these for review last year but their UK importers/suppliers failed to deliver despite repeated requests, and if that's their service to reviewers, what's it like for the ordinary customer?
So I had to buy some to be thorough. Michell produce Tendercups to match their Tenderfeet, but these make no special claims at vibration control, merely providing optimum termination for the Tenderfeet, being manufactured from the same grade of aluminium, and minimising damage to the shelf.

The Polycrystal PD-1 Point Discs will be a very useful product if they work, especially at $2.95 each! So many speaker stands and shelf supports have been manufactured with fixed welded steel spikes, since the early 1980s when such products became fashionable. The once ubiquitous Sound Organisation table keeping the once ubiquitous Linn Sondek half-a-metre above the floor had bent steel lugs cut to a point sprouting sideways from the frame near each corner, to support the chipboard shelf (and they told me in about '94 that they also tried mdf and found it didn't sound as good) leaving little scope for further fine tuning until now. The Polycrystal point discs are supplied in sets of 4 but will remove the possibility of 4 spikes levelling themselves into the shelf by deformation. The only way to overcome this is to use just 3 atop the 3 of the spikes that will be more stable, given the centre-of-gravity bias that any equipment has (usually to the rear where the mains transformer sits). For extra stability a soft support product like the BrightStar Isonodes may be necessary in the other corner of 4 sided supports. If only the audio world woke up to the fact (to misquote George Orwell) that "3 points good, 4 points bad".

The Polycrystal Point Discs are a more specialised spike interface than any of the others. The cores are manufactured from instrument brass, a metal with very different mechanical properties than steel or aluminium. The brass blank is then coated on all sides with a thin layer of Polycrystal material, "although the application process is entirely different between the brass core products and the solid Polycrystal products" according to Robert Stein of UltraSystems. You can find more description for yourself on their website, but don't forget to use your back-button to return to the review rather than wandering off into a cyber-trail of interesting looking links; I WILL BE ASKING QUESTIONS LATER SO PAY ATTENTION.

My Michell Gyro SE sat on the same support as my Orbe SE, but during the turntable change I stripped it all down & carefully reassembled it and the test results are identical. A 10mm laminated-glass shelf (after trying various materials including Origin Live's own selected grade of 18mm HDF) rests on an "Ultra" version of the original Origin live wall frame. I tried many different supports for my '91spec Linn Sondek (notoriously sensitive to shelf types) and this was the best by such a wide margin that I consider it the reference for suspended subchassis turntables.
Sadly it is not made anymore, but if I repeat this mantra regularly perhaps Mark Baker will restart production. Actually there was never an official "Ultra" version of the wall shelf as there was for his floor tables, but this one arose out of telephone conversations in the late 80s. Mine has been modified in 3 ways:
1 Chrome plated to make it less heavy 80s looking
2 10mm laminated glass shelf suits Gyro SE better than HDF
3 Brass chains replace springy nylon cords
4 Rear tension bar filled with kiln-dried sand
The chains modification also arose from a conversation with Mark Baker who noted that he chose the cords because he thought they were more domestically acceptable than chains, that he had also considered, but didn't think there would be any sound quality difference between either. I tried chains out of curiosity when installing in a new location and heard a slight improvement in sounstage focus and size on the Gyro which is already a strength of the Gyro but a weakness of the Linn, where chains had tightenned the bass a little.

[Orbe on Point Discs]
Point Discs both sides of shelf

The spike interface products are therefore being tried in an already optimised vinyl replay situation. If they have a detrimental effect here it could be because the set-up is already tuned. Just to complicate the evaluation further, the Origin Live shelf has a tunable frame as my sketch shows:

[Origin Live frame]
Origin Live frame

The outrigger bar has preload screws at each end. When these are tighter the bass tends to extend deeper and initially tighter sounding too. Tighten the screws a little further and the bass begins to get fatter, gradually becoming overblown. Meanwhile the music also tends to fall apart as the rhythm & timing become incoherent and the soundstage collapses. When the screws are as loose as possible without disconnecting from the wall the rhythm tends to become more coherent and the pace picks up, but the bass falls away. This effect was very noticable on the Linn but is even present with the Michells, which tend to be less situation dependent than other subchassis turntables. Mark Baker originally developed this shelf in the 80s using the ubiquitous Linn. The screws are set in my favoured position, about one quarter turn from first contact. The final test excercise does require them to be adjusted several times.

First test places each product in turn on top of the 3 upward facing spikes between the frame and the glass shelf. There is absolutely no doubt about the results. The Michell Tendercups, the RDC cups and the Origin Live discs +Blu-Tac (designed for speakers but not for this location) are all better than the spikes directly touching the shelf in terms of improved articulation of individual instruments and individual notes. The Polycrystal point discs are best of all, without qualification in any performance parameter.

The first effect is an apparent lowering of the noise floor. Given that my Gyro SE has the dc motor and big Gyropower VC power supply I suspect that only part of this could be mechanical noise from the drive system. Perhaps it is from airborne vibration exciting the frame and shelf and groundborne vibration conducted through the point loads on the wall. The wall is heavy Derbyshire gritstone 250mm thick and directly coated on both sides with heavy lime 'renovating' plaster.

Rhythm and pace seem unaffected, but timing coherence between different parts of the frequency spectrum seem tighter. This makes for a more musically satisfying experience with every lp played. Additionally, initial transients seem quicker and clearer, while decay sounds longer & further. This makes the contributions of every instrument more tangible. Each instrument is able to be heard more clearly in the mix or on the stage. There is also a slight reduction in glare making for improved clarity of the highest frequencies, cymbals benefiting especially.

The Polycrystal point discs are lower profile than the other 3 products. Only the Polycrystal point discs could be tried under the pointed feet of the Gyro SE. Because these only support the frame that supports the subchassis, the RDC & Michell raise the platter out of alignment of the motor pulley as the motor stands directly on the shelf. There are 3 belt grooves on the Gyrodec platter, and 2 on the motor pulley (the upper one for 33rpm & the lower for 45rpm). I normally use the middle platter groove for both 33 & 45 as I prefer not to stretch the belt from one to another too often. With the Polycrystal point discs in place the belt needed to be in the bottom platter groove to align with the 33rpm pulley (45rpm pulley being misaligned). It would be possible to adjust the supension down a little if these are to be a permanent feature of the set-up. The Michell suspension has more scope for adjustment than most while maintaining good vertical bounce and good linearity on the belt plane.

The results with the Polycrystal point discs on both sides of the glass shelf is a further gain in the areas already described. This is a slight improvement on top of the earlier gains, especially in lower noisefloor and glare. If you're paying the postage on one set you may as well order two sets. I am going to buy the review samples.

The final excercise I'll try with these little gizmos is between the preload screws and the wall. The point discs can be bought in any quantity. I received 8 and the Gyro has 3 feet and the Origin Live shelf also has 3 spikes so that leaves me the 2 spare that I need for this experiment. When I first tried my Origin Live shelf it was mounted on a 230mm victorian brick wall faced with finishing plaster. This soft plaster was easily damaged and compressed by the screws which soon became slack as a consequence of this. I tried using plain steel discs to protect the wall and the stability of the set-up but this had a detrimental effect on the sound and I eventually settled on a couple of slivers of hardwood that sounded identical to newly tightened screws direct on plaster. My current wall does not suffer such a soft surface so I have not tried anything in this location before. This test is undertaken with the point discs still in place on either side of the glass shelf.

The outrigger preload screws are a tuning device so care has to be taken to maintain a similar preload with each product. With each product the best result comes with the minimum quarter-turn preload; this prevents the frame rocking about the axis of the central point load on the wall, which being horizontal and perpendicular to the pickup playing arc would affect bass articulation and information retrieval. With each device in place the preload changes become more audible than when the screws directly touch the plaster of the wall. Timing, coherence and soundstage all suffer with every quarter turn tighter. The centre of gravity of the Gyro SE causes the load to bias toward the left preload screw (viewed from the front) which is probably not ideal.

[Origin Live preload outrigger]
Origin Live pre-load outrigger on RDC cup

The RDC cone cups seem to slow the rhythm compared to the alternatives, even though they appear to offer no compliance. I could understand this effect if they were compliant as it would alow horizontal movement of the whole motor-platter system. The soundstage also narrows, which would be explicable if there were any loss of vertical information, but intuition suggests the arrangement should only affect vertical modulation. I have no hypothesis to explain what I hear but it is repeatable.

The point discs are again the best interface in this position. Despite Andy Warhol's strange production values, the Velvet Underground's White Light / White Heat benefits greatly from the Simply Vynil 180gm reissue, no more so than the 17minute grind of Sister Ray on side 2. The highest compliment I can pay the Polychrystal Point Discs is that this track felt even more uncomfortable, disturbing even, with the Point Discs in place. Edgy becomes edgier, the tense rhythmic interplay becomes tenser, the selection of distortion phenomenae become more distinct. The track's relentless descent through the highlights of the low-life of the city remain rivetting to the end.

Under speakers

More audiophiles will have welded spikes on speaker stands than any other location. Where there are 4 spikes (most commonly, aaaargh!!!) the only solution will be to use the point discs under 2 of them and rely on cabinet deformation of the other 2 to maintain stability. I did try 4 point discs and the results here are consistently that 2 are better than 4 but three are best of all. Two are also significantly better than none.

Trying with BBC LS3/5a (8ohm) atop Target sand & shot loaded stands they are unsuccessful. The LS3/5a use damped thin-wall (12mm birch-ply) cabinets (after Barlow's research) which the Target stands really suit. Their symbiosis may be due to the mobile mass of the sand acting as a sink for the energy levels of the thin walls. Perhaps the Point Discs might interupt the energy path (clumsily expressed, I know), but this is only a hypothesis. The point discs are more successful with open frame stand types.

Cabinet colouration seems reduced with 2 of these $2.95 discs in place. Even on the spikes of an Origin Live stand they outperform the steel discs+blu-tak supplied with the stands. The cost is so low and the benefits so straightforward that there is no point in further discussion.

The only caveat is that 4 point discs, and 4 OL discs & 4 tendercups & 4 RDC cups, all sound worse than spikes into wood, one way or another. With 4 interface gizmos there is a combination of lost information & increased glare or forward presence-region or ragged top-end. With 2 spike interface products the OL originals majored on increased information, especially micro-dynamics, and a subtle improvement in instrumental timbre. 2 Point Discs achieved similar results but with reductions in colouration plus gains in treble clarity. The pitch of the highest frequencies, especially percussion (noticable on Tan Dun) also become more explicit, which helped greatly with my struggle to encounter modern Oriental composition.

Three points of rigid contact consistently outperform four. Where four fixed spikes are already forced by a stand manufacturer treating two spikes will bring benefits in articulation an colouration. Alternatively, treating three of the spikes will be better still, but only if this does not make the speaker unstable and prone to be knocked down onto small children or pets.

[Move & Groove]
Move & Groove


No brainer recommendation. If you have equipment racks or speaker stands that aren't otherwise fine-tuned by the manufacturer but are fitted with fixed steel spikes these will usually be a disproportionate improvement for their cost. Only one combination (LS3/5a on sand filled Target stands) failed to benefit but this is an already optimised situation. I repeat (endlessly) that 3 points of contact are usually better than 4. The Polychrystal Point Discs perform the simple task of optimising the interface between shelf & stand simply...and very economically too. The Tendercups, RDC cups and Origin Live discs are also an improvement over the untreated condition. Old racks & shelves gain a new lease of life and system tuning takes one step further.

Music enjoyed during this review

For the turntable tests on vinyl of course:
White Stripes: Digital is Evil, live in Detroit & Eire
Little Feat: The Last Record Album, Warner K56156
Little Feat: Sailin Shoes, Warner
Velvet Underground: White Light / White Heat, 1996 Simply Vinyl SVLP200 180gm reissue
Michelle Shocked: Arkansas Traveller, London 512-189-1
Flanders & Swann: High Fidelity, from At The Drop of a Hat, EMI ONCR511
Dennis Brown: Concentration; The Crystalites: Concentration (version 3); 1972 Move & Groove/Trojan TJHTE009
Lee 'Scratch' Perry: Cloak & Dagger (Tommy McCook & The Upsetters); Sharpe Razor (The Upsetters); Dub Organiser (Dillinger); Cloak & Dagger (dub plate pressure version), Trojan TJHTE019
"Trojan Limited Edition Dub Plate 45" these 10inch reissue discs capitalise on the nostalgia & romance of the old white label prereleases that were often badly cut in a hurry, whereas these Trojan discs are top quality items, but sadly cut from the modern digital remaster rather than the 1973 analogue tapes. This last one plays at 33rpm despite the label!

The speaker stand test also included the cd:
Tan Dun: Out of Peking Opera; Death & Fire; Orchestral Theatre II: Re, Ondine ODE864-2

Copyright 2005 Mark Wheeler - www.tnt-audio.com

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