What's a TAD Spotmat...? That's me fooling around with Malcolm Coulson's original SpotMat design.
When Malcolm sent me his SpotMat to try I was a little less than excited. Ho hum, I'd tried different mats on the Thorens and....well none of them made any huge difference. Subtle improvements, maybe, but nothing that would wake me up to take notice. The SpotMat pulled me out of this blase' outlook when I noticed a much weightier bass line that was also better textured. Mids were more natural sounding and with an improved sense of presence. Highs have more detail and hang in air longer. It's as if the turntable was now pulling better quality info out of the grooves. Not surprisingly, the already good Thorens background silence had improved as well. All this from a platter mat...!
Above photo #1. This is my first SpotMat variant. My thinking was to duplicate Malcolm's layout pattern of the "spots", increase the area of the paper and add an additional paper layer to stiffen the mat and help it lie flat against the zinc platter of the Thorens. Why...?
Well......, in a sense I wanted to test to see if the small 9.5 inch diameter of the Spotmat was absolutely crucial. I also wanted to test to see if the heavyweight watercolor paper Malcolm uses is also a requirement or if other materials might be used.
Using a 3D cad program, I laid out the pattern. This gives me an accurate, concentric pattern to cut to and also markings for gluing the cork spots to. While I was at it, I thought I might try adding a graphic to add visual interest. Well, it was a rough draft. Listening tests suggested that the sound of this mat (#1) was indistinguishable from SpotMat.
Above photo #2: This is my second variation. Emboldened by results from the first mat, I chose to try some different materials for the mat but stayed with the same mat diameter and spot pattern as the first mat. Materials in this mat are heavyweight canvas cloth bonded with neoprene based contact cement to a clay based heavyweight glossy photo ink-jet paper. In practice, the canvas backing was just slightly less prone to lie flat than the first mat but proved to be the equal in sound to both my first mat and SpotMat. No difference. As I had thought. Continuing to think graphically, I worked up the above drawing for this mat. Another rough draft. 'Still looking for a graphic pattern that "works for me". This won't be it.
Above photo #3: The third variation. Although the spot pattern remains unchanged, this mat is more radical. Visually, it is apparent that I have extended the mat material out to the platter rim. What made this possible was a trip to the store to buy some 13 x 19 inch computer paper. Man that stuff gets expensive...! Here I've got.....watercolor paper (ink jet style). $25 for 20 sheets. The watercolor paper doesn't take the ink like the clay based glossy paper so I found that detailed rendered imagery didn't really work out well. Everything gets softer and less detailed. Crap...! The 13 x 19 high gloss paper is twice the cost. The above pattern is a simple line drawing. At least that works. But that's just the graphic pattern. What really sets this mat apart from the others is the composition of the mat material. I've got 1/64th inch sheet lead bonded between heavy canvas on the bottom and the water color paper on top. Again, neoprene contact cement is the bonding medium. There were problems noted with "dynamic warping" of the mat after a prolonged period of spin. Care had to be taken when handling this mat lest the lead sheet within the layers bend permanently. Sound is ok but nothing to get worked up over.
Above photo #4: The 4th variation. Same mat composition as #3 except cork pads are .12 inches thick and there is a change to the graphic. Mat #4 has a total thickness of .180 inches. It would make no sense to make a mat any thicker due to length of center pin. A VTA adjustment will be needed with this mat which is .060 inches thicker than mat #3. After VTA adjustment session, listening evaluation revealed no improvements. Considering the extreme thickness of this mat, I have moved on to mat #5 seen below.
Above photo #5: Fifth variation. Same canvas, lead, paper mat composition as with #3 and #4, but with an altered cork spot layout. Just three spots equally spaced concentric to the center pin. Cork thickness is returned to .06 inches as in mats 1,2 and 3. Overall mat height is the same as with mat #3.
Operational note: Record warps now can have more vertical travel with mat #5, but this may be altered by 'clocking' rotational position of the record as it rests on the mat. This may not be a negative, or it may be something that can be tolerated if overall sound is good enough. Still assessing.
Cautionary note: mats #3,4 and 5 are easily bent due to the soft layer of lead in their composition. Handling of these mats when taken off the platter is a delicate issue and considerations for safe "flat" storage off the turntable is another problem.
Above photo #6: Mat #6. Nine cork pads are included for improved record support when compared to mat #5. Composition is different for this mat. Bottom layer is still heavy canvas. The inner laminate, however, is now PVC (vinyl). Top layer is still heavy paper with the now familiar Celtic symbols design.
The PVC layer is actually a cut down vinyl Lp...:-) Finally, I found a use for my culls....! This mat sounds better than any of the "lead core" mats tried previously.
There are some negatives to this particular version. I've put together a half-dozen of these in an attempt to cure a problem seen with the first. The mat would play beautifully for the first few sides and then begin to curl upward at the edges. Yes........the mat rim would begin to lift up off the platter curving into a dish. The weird part is that after leaving the mat sit overnight I would find the damned thing sitting flatly on the platter in the morning. Spin it and it curls. At first I wasn't sure what the cause might be. I thought it could be the paper top layer, or the canvas bottom layer or just weird vinyl. Turns out it was the heavy duty commercial grade contact cement I was using. When I made a mat using household grade "Elmers' spray on adhesive" (general purpose) the mat did not exhibit the curling behavior. There were some problems with adhesion between the layers, though. I also tried polyurethane adhesive to no avail. Same curling behavior as with contact cement. Vinyl...........weird stuff. Mat 7 won't use vinyl. Rats. I was liking this one............. at first.
7) Spotmat #7 (link to page) Fixes problems encountered with Spotmat #6 by substituting core layer with different material. more details at link.
A simpler spotmat. details at link
Simpler, yet again. This time no paper, just cork. details at link
Same as #8 only in natural gum rubber
Same as #8 but in foam sheet. Hint......this is the best sounding Spotmat so far....!
Dimensioned drawing for spotmat No. 7 thru No. 10. downloadable pdf file : link Just open by clicking or save to your hard drive.
Posted by user510 (A) on January 20, 2004 at 10:46:09
In Reply to: Re: Mat #6.....the saga continues. posted by jnorv on January 19, 2004 at 20:22:29:
"I would think that a somewhat random distribution of the dots would be better since there would be no dominate resonance frequency. Sort of like using the magic ratio in room dimensions."
That is a thought worth exploring. It would be nice to be able to run a computer simulation of the effect with different dot patterns. Mr. Gratsias would probably approve... ;-)
The spot pattern with mat #6 is evolved from the minimalist mat #5 which attempted to use only 3 points of support. Even records thought to be flat didn't ride well on mat #5. The nine spots are considered to be a minimum that will still adequately provide a stable bedding for the record to ride. The spot pattern is concentric and is an evenly spaced pattern of threes. Threes dominate the graphic design, also but that's a different matter. It might be interesting to experiment with randomness in the spot pattern but within parameters that will provide record support to the level needed.
Of course the idea behind Spotmat is for the record to have minimal support contact and with sufficient air underneath. The stylus tracing the groove excites the records vinyl into vibration relative to the modulations within the groove being traced and no doubt is affected by effective tonearm mass as well as cantilever stiffness. The record is allowed to vibrate freely 'in air' and is thought to have --more or less-- exhausted / dissipated its resonant energy before a complete revolution has been turned. Listening to Willbewills' Spotmat is fairly convincing that this must be so. Yet we have no scientific measure to support this. I see the mat design and then hear it and note the differences heard. Trial and error.
My take with mat #6 has been to make use of the cork contact spots not only as support for the record but as portals for resonant energy to pass into the inner laminate where it (the energy) finds ....... more vinyl to resonate within and perhaps dissipate more completely. An energy drain effect. That is the thought. Yet the only measure is for me to listen to a familiar album and compare to a previous mat. ***
*** VTA considerations are accounted for. Currently I am keeping my mat thickness between .120 and .150 inches with my different versions.
VTA is optimized for each mat before drawing any conclusion from listening. BTW, the SME tonearm provides a convenient and highly repeatable method for vta adjustment using feeler gages to measure the amount of change.
lots o fun.
Mat thickness and VTA:
In brief, if you change the overall height of your platter mat, the vertical tracking angle of the stylus/cantilever, as it rides in the record groove, is altered. Try the link above for a graphical explanation of VTA. The mats in this article each have different overall thickness. The means that an adjustment to VTA is required before a fair listening evaluation can be made. Here are the mat thickness values.
TD160 Rubber mat: .150 inches
DIY "none-felt" mat: .156 inches
Malcolm's Spotmat: .095 inches
TAD Spotmat #1: .090 inches
TAD Spotmat #2: .105 inches
TAD Spotmat #3: .120 inches
TAD Spotmat #4: .180 inches
TAD Spotmat #5: .130 inches
TAD Spotmat #6: .140 inches
TAD Spotmat #7: .135 inches
TAD Spotmat #8: .125 inches
TAD Spotmat #9: .125 inches
TAD Spotmat #10: .155 inches
setting VTA on a TD160 (link to page)
About the graphic pattern:
Line drawing pattern in mats #3,4,5, 6 &7 are designs with repetitious use of ancient Celtic symbols. I thought I might as well "cast a spell" on the music that gets played. In a good way, of course. The three legged things running around the perimeter are called "Triskelions". Both the ancient Greeks and Celts used this symbol. Triskelions are associated with progress and competition. The three lobed center objects are called "Triquetra. The word is Latin for three-cornered. The Celts and the Druids believed the number 3 to have extreme power. This symbol came into popular use during the Roman occupation of Britain, but can also be found among more ancient Celt artifacts. The double spirals around the perimeter are far more ancient and the exact meaning is not known.
Also the ink, I'm told, is derived from the digestive tract of the Bohemian Dung Beetle of Indonesia. This very special ink is said to have enzymes that "consume" resonance....! ;-)
Illustration below: Why you wouldn't use a record weight or clamp in combination with any of the Spotmats I have pictured above:
The spotmat variations that I have tried all attempt to isolate from the platter and platter bearing by offering the least amount of physical support. Ie, fewest spots. Also, I have found that Thorens players such as the Td150, TD125 and TD160 do in fact generate some bearing noise in the form of rumble. For this reason I have placed the cork/foam spots a considerable radial distance out from the main bearing.
If, however, one tries one of the popular commercially made record weights or, perhaps, a Thorens Stabilizer, there will be no record support directly beneath any of these weights. For this reason the weight will tend to dish the record upward at the outer rim of it. See above illustration. If you want to try one of these weights, I'd guess you will prefer to use another type of platter mat; one that offers record support directly underneath the weight.!!!