thebes Posted February 7, 2017 Share Posted February 7, 2017 I've got a Technics SP25 , and built a Baltic Birch/MDF sandwich plinth for it, but am not pleased at the results. The stock factory base for this is described as being "constructed from a heavy, acoustically dead, rubber material". I found this material online and a four by six feet piece weighs a hundred pounds which is seriously heavy. I'm thinking resonance would not be a problem and it would be in keeping with the heavy base the Technics people originally designed for it. http://www.rubberflooringexperts.com/exercise-fitness/thick-mats/shark-tooth-heavy-duty-floor-mat.html I want to do a 20" by 15" plinth so it would weigh about fifty pounds before I cut which is essentially a large circle, so maybe 30 pounds when I'm done. The leftover rubber could be used for feet. Sound like a plan or a waste of time? I ask because shipping cost on something this heavy have got a to high. Quote Link to comment Share on other sites More sharing options...
lakedmb Posted February 7, 2017 Share Posted February 7, 2017 May be worth it. The 2x3ft piece is $39 and shipping is $29. Not as bad as I would expect and a bit more manageable than the 4x6ft piece. For just under $70, I would probably give it a try. Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 7, 2017 Share Posted February 7, 2017 Boy, I don't know what all you might be setting yourself up for. It might be too heavy for what's supposed to hold it up, for one thing. One thing you could do IMO is to contact the manufacturer to get an opinion. Technics still seems to be around. If it were a Basis and AJ Conti were still alive, it would be fascinating to hear what he would have to say. In fact, if it were a Basis, it would be interesting to see what the current/remaining engineering talent at Basis would have to say. Not a good idea for a Technics, however. I got the idea over the years that engineering a TT was very difficult, with a lot of factors entering in. The staff at good audiophile companies seem to be very cooperative, so I'd at least explore contacting someone there. Quote Link to comment Share on other sites More sharing options...
Chris A Posted February 7, 2017 Share Posted February 7, 2017 Looks like it's made from recycled auto tires. If so, it's probably fairly high durometer material (i.e., stiff). I'd give it a shot. You can judge when it arrives whether or not it will deflect visibly under the weight of the table mechanism. If so, you can cut the material to be wider than the table to improve stiffness. The biggest issue with turntable is basically noise and isolation, after you buy something that has low wow and flutter, and a reasonable tonearm that tracks well even with warped records, the rest is isolation from the environment. Turntable manufacturers used materials that the consumer would accept, not necessarily what would work the best. I think your idea is both creative and going in the right direction. A couple of years ago I bought a test record which included a silent track. When I put the needle down on it, I recorded the following: So those peaks at 60, 120, and 240 Hz were the biggest issues, which were synchronous motor noise frequency plus second and fourth harmonics. I isolated the motor from the table a bit more using bigger rubber washers on the Empire 398 turntable motor suspension points. That worked nicely to reduce those peaks. The turntable sits on an window ledge, which is extremely stable and isolated from everything else...like the floor (concrete slab) and other sources of vibration. Having a plinth that absorbs vibration rather than transmitting it to the platter or the tonearm would be a real advantage. Chris Quote Link to comment Share on other sites More sharing options...
thebes Posted February 8, 2017 Author Share Posted February 8, 2017 4 hours ago, lakedmb said: May be worth it. The 2x3ft piece is $39 and shipping is $29. Not as bad as I would expect and a bit more manageable than the 4x6ft piece. For just under $70, I would probably give it a try. That's what I was thinking, especially given the difficulty in finding a factory plinth. Larry, I can't argue with your posits at all, but people have been experimenting with plinths as long as there have been turntables. I'm sure you recall all the console era pieces where they'd sell you the table and always include a blueprint for cutting your own plinth in case you wanted to install it under your Tikki bar, sideboard, home built console, or whatever. I'd love to tap the knowledge or Technics but I'm not sure it's there anymore. You may recall about 6 or 8 years ago they discontinued their SL1200 turntable after a 30 year run,. It was primarily used for DJ work, but I'm pretty sure they sold more of those than any turntable in the history of turntables. The table sold for a few hundred dollars cause they had the molds, templates etc. and there was little or no tooling involved in cranking them out over the years. Fast forward to last year, they decide to re-issue the table and it's now like two or three grand. Why? Just greedy? Nope, the second they stopped production, they literally and figuratively threw away every tool and die to make one. The point of the above is that the guys who could answer my questions are long gone. Quote Link to comment Share on other sites More sharing options...
thebes Posted February 8, 2017 Author Share Posted February 8, 2017 Hey Chris I really appreciate your thoughts on this. I had that exact model Empire. Loved it!. Classic looks and a wonderful sound. But the rumble was very noticeable, and while the open space under the plinth helped in the creation of that magical sound, a tap on the plinth with its resulting resonance would reveal the shortcomings of using that particular approach. Still, I suspect if there was a way to isolate that Pabst asynchronous motor from the table, I'd be willing to live with the plinth. Hey, I'd just think of it like it was the body of an acoustic guitar. Quote Link to comment Share on other sites More sharing options...
Chris A Posted February 8, 2017 Share Posted February 8, 2017 Well, good thing that I don't use it very often, eh? Must be terrible...until you figure out how to isolate the motor noise. Then it's pretty good. A little engineering sometimes makes a big difference. You still interested in your plinth upgrade? Chris Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 8, 2017 Share Posted February 8, 2017 Marty, there was a recent article in the NYT about the resurrection of the Technics 1200 TT. I don't think the co. is gone. There's probably a 1-800 #. Quote Link to comment Share on other sites More sharing options...
jorjen Posted February 8, 2017 Share Posted February 8, 2017 21 hours ago, thebes said: I've got a Technics SP25 , and built a Baltic Birch/MDF sandwich plinth for it, but am not pleased at the results. The stock factory base for this is described as being "constructed from a heavy, acoustically dead, rubber material". I found this material online and a four by six feet piece weighs a hundred pounds which is seriously heavy. I'm thinking resonance would not be a problem and it would be in keeping with the heavy base the Technics people originally designed for it. http://www.rubberflooringexperts.com/exercise-fitness/thick-mats/shark-tooth-heavy-duty-floor-mat.html I want to do a 20" by 15" plinth so it would weigh about fifty pounds before I cut which is essentially a large circle, so maybe 30 pounds when I'm done. The leftover rubber could be used for feet. Sound like a plan or a waste of time? I ask because shipping cost on something this heavy have got a to high. So it is 3/4" material? How many layers you thinking about? 2, 3? Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted February 8, 2017 Moderators Share Posted February 8, 2017 I do have a question, this rubber looks really tough and would probably look good. But the question is what is this supposed to do, just support the TT or to separate it from vibrations from itself and elsewhere ? i would think a dense heavy rubber might not do so well ? Wouldn't something lighter and designed to isolate vibrations be better ? Something "like" bubble wrap but made better with layers of other vibration absorbing layers between layers of air bladders. I don't know, as you can see, just trying to think of something to better absorb vibration than a dense rubber. Or does the dense rubber absorb vibrations ? It does when supporting a car but a TT is lighter and much more prone to a tiny bit of vibration. As you can see it was all just guesses. Just add magnetic levitation to the TT and have it float along, ok I'll quit now Quote Link to comment Share on other sites More sharing options...
thebes Posted February 8, 2017 Author Share Posted February 8, 2017 Again, I'm thinking of pursuing rubber because the factory plinths for this specific model were made of some version of rubber, and were designed to dampen vibrations etc. Here's some literature about this plinth from the Vinyl Engine website: "The Technics SH-15B2 base has been specially developed for the SP-15 and SP-25 quartz direct drive turntables. The entire cabinet integrally formed with a special visco-elastic material has its main sections such as the turntable, arm panel etc isolated for vibration damping construction. With the dust cover and insulators directly coupled to the material, the unit has been designed to achieve complete vibration damping. Note that tonearms attachable to this unit are limited in their dimensions and configurations. Specifications External dimensions: 526 x 172 x 403mm Weight: 10.5kg (including dust cover)" Please notice the weight . That's a heavy plinth considering that the plinth is only 1 and half inches thick. Now, not all turntable builders consider the heavy plinth approach to be optimal, or they said that to cover the fact that they didn't want to spend the extra money on a heavy plinth. The same type of arguments are also used in debates about platters, heavy versus light, and then there is the whole debate about type of arm masses, but these conundrums are not the subject of this thread. Jorgen, I'd probably go for the same 1 1/2" thickness used in the original with about the same dimensions. Depending on how elastic the material is when I get my hands on it, I might choose to use an over and under armboard to make sure the arm does not move at all. Larry, this table was built long ago. The guys that designed the table and the plinths are probably long gone from the company, if not dead. The reason I'm considering this approach at all is these plinths are basically unobtanium . It came with a very thin wooden plinth, obviously home built, and the thicker one I built for it really, really echoes when I thump it. The rubber under consideration is built from recycled tires. Tires have threads in them. I'm thinking this could also be beneficial because since they are chopped into the rubber at random, they could randomly disburse any unwanted resonance in a fashion new solid rubber might not be able to do, if that makes any sense to the dear readers of this thread. Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted February 8, 2017 Moderators Share Posted February 8, 2017 2 hours ago, thebes said: I'm thinking this could also be beneficial because since they are chopped into the rubber at random, they could randomly disburse any unwanted resonance in a fashion new solid rubber might not be able to do, if that makes any sense to the dear readers of this thread. Seems to make sense, this tread had just got me wondering and thinking, not always a good thing. Quote Link to comment Share on other sites More sharing options...
seti Posted February 9, 2017 Share Posted February 9, 2017 I've never seen anyone use rubber but a friend has used paper stone and slate. I just used multiple layers of 1 inch baltic birch plywood. Quote Link to comment Share on other sites More sharing options...
mungkiman Posted February 9, 2017 Share Posted February 9, 2017 9 hours ago, jorjen said: So it is 3/4" material? How many layers you thinking about? 2, 3? 5 layers, if he actually means 50 pounds... Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 9, 2017 Share Posted February 9, 2017 8 hours ago, thebes said: Larry, this table was built long ago. The guys that designed the table and the plinths are probably long gone from the company, if not dead. The reason I'm considering this approach at all is these plinths are basically unobtanium . It came with a very thin wooden plinth, obviously home built, and the thicker one I built for it really, really echoes when I thump it. Marty, see https://www.nytimes.com/2017/01/01/business/panasonic-technics-hiphop-turntable.html?_r=0 OK, Panasonic is the one reintroducing the SL-1200, not Technics. While they may not be amenable to a contact with a new TT, I don't think it would cost anything. The same goes for trying to have a conversation with a young designer at VPI or some other quality turntable. Quote Link to comment Share on other sites More sharing options...
thebes Posted February 9, 2017 Author Share Posted February 9, 2017 12 hours ago, mungkiman said: 5 layers, if he actually means 50 pounds... No. The materiel will weigh 50 pounds, but then I have to cut a 12" hole in it to fit the table, which should get it down around 30lbs or so. Using two layers results in the same thickness used for the original manufactures plinth. The original plinth weighs 21 lbs. Quote Link to comment Share on other sites More sharing options...
mungkiman Posted February 9, 2017 Share Posted February 9, 2017 If 48" x 72" (3456 square inches) weighs 100 pounds, 20" x 15" (300 square inches) weighs close to 10 pounds. Quote Link to comment Share on other sites More sharing options...
thebes Posted February 9, 2017 Author Share Posted February 9, 2017 Oh sure, bring math into it. Ok, I'm going to double up the layers, which are 3/4 inch thick to get to the 1 1/2" thickness of the factory plinth. I 'm going to buy a 3' by 4' piece, which is half the size of the full sheet. So that should weigh 50lbs before I do the cutting and trimming, hole for the arm etc. I can go a bit wider, say 15' by 22" if I need to get the weight up a bit. Since you can actually calculate and such do you know what these dimensions are when translated into inches? External dimensions: 526 x 172 x 403mm Quote Link to comment Share on other sites More sharing options...
mungkiman Posted February 9, 2017 Share Posted February 9, 2017 20.7087" x 6.77165" x 15.8661" Quote Link to comment Share on other sites More sharing options...
thebes Posted February 9, 2017 Author Share Posted February 9, 2017 So pretty much what I will be doing except the height includes the feet, and dust cover plus the plinth width which I figured at 1 and 1/2" from dimensions given in the actual owners manual for the plinth posted n Vinyl Engine. So I should be good to go and probably come in at around the 23 lbs of the original? Quote Link to comment Share on other sites More sharing options...
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