Vintage DD turntables. Are we living dangerously?

Ct0517
Thank you, the ET2 I Beam is an excellent example of an I beam - no plywood, no lead or glue, just a piece of plastic with flanges top and bottom to give axial and structural rigidity - the whole piece being an extrusion to form the I. Richardkrebs may have forgotten what the ET2 I Beam looks like as he has removed the decoupled I Beam from his ET2 and replaced it with a much heaver M10 bolt, thus removing one of the key patented benefits of the ET2 design, the decoupled counterweight which was designed to keep the high horizontal mass of the ET2 as low as possible and minimise bass peak resonances. The ET2 is an excellent example of using I Beams and large thin walled tubes to deliver a light but rigid structure.

Aigenga,
"On the subject of platter mats I just want to re-iterate that I am using a lead mat glued to an Achromat. I thought that Fleib or someone else was about to try the same thing and wonder how that worked for them?"

I'm experimenting with this now, and I'm wondering about the details of your mats. I bought a 3mm Achromat thinking 5mm might be too thick with an additional 2mm underneath.
BTW, the 3mm version seems to have deficiencies when used alone.

As it turns out, once flattened, roofing lead is more like 1mm thick and weighs about 510g. It seems to greatly improve the Achromat, but I suspect it would be better with the 5mm version. The question is, would the 5mm mat with 1mm of lead, outperform the 3mm with 2mm of lead.

The Achromat is somewhat of a surprise looking like "fine" cardboard. It's more like 2.5mm and unless you glue it down the edges tend to lift if you only clamp the LP on the spindle. I find myself listening to the last 50mm of a side, for evaluation.

Like most of you I have a collection of mats. Mine includes a 3mm hard acrylic, and one of expanded foam - also about 3mm. So far best results seem to come from the lead in the middle with either the foam or acrylic on the bottom and the Funk on top. The foam combination is a little warmer. The acrylic seems faster/cleaner, but either combo sounds pretty good.

I'm thinking of die casting lead mats of different thickness/weight. A lead undermat seems to have great potential. Perhaps thicker sheet lead is less trouble.
Regards,

Thanks for changing the subject from vituperation and the definition of an I-beam to mats, a subject we can all sink our teeth into, or not. Mats are crucial in determining the sonic character of a turntable, all other things being equal. Thus inevitably one's choice will be to some degree a matter of taste. After mucking about with several different types, I have settled contentedly on the Boston Audio Mats 1 and 2. They are as good as or better than everything else I tried, but I do not kid myself that there could be nothing better out there that I have not tried. On the L07D, I stick with their stainless steel platter sheet, although I am otherwise convinced that the BA Mat 2 sounds a bit better than an SAEC SS300 (another metal mat), on my SP10 Mk3.

Lewm,
You might like to try a copper mat on your SP10 if you haven't already. In a direct comparison of the L07D stainless mat, Boston, and a few others - the copper mat came out as the most complete in my experiments.
A word of caution - for DD turntables mats should ideally weigh the same as original as the speed servos are optimised for the mass of the standard platter. For example in the L07D the manual carries a warning that if you run the platter without the mat the servos will not work properly.

Dover, I totally agree that it is wise to use a mat that approximates the weight of the OEM mat on a DD turntable with servo control. I have preached that gospel for years, but lots of folks ignore the principle and claim to be getting away with it. This is one reason why I stick to the OEM platter sheet on my L07D. That and the fact that the L07D sounds so terrific. I do suppose that there is a copper mat out there that would approximate the weight of the platter sheet (5 lbs, I think). Why do you suppose that copper might sound significantly different from, not to say better than, stainless steel? It's also the case that the L07D servo was deliberately designed to exert a much looser control on the speed than does the Technics servo, for one example. I think it only activates when there is +/-3% speed error.