A sturdy wall mount support for the turntable
Design and fabrication at: The Analog Dept.
To be regarded not as a potential product, but rather an experiment in turntable support systems. OK, let's be kind and call it a learning process.
Below 3d imagery: Pre-visualizing the wall mounted rack for my Teres. I had decided that I needed to wall mount my Teres in my upstairs flat. Problem is, nobody sells a TT wall rack robust enough. I might as well build one. That's what I thought, anyway.
Material is to be mild steel in 2 shapes. 1 inch square (.07 wall) seamless tubing, and 1/8 inch thick plate (2 different widths). The various pieces are to be welded together using a Victor oxy-acetylene set. The completed rack is to be bolted to the load bearing stud structure behind the sheetrock wall with six 5/16 x 3 inch lag bolts. (lag bolt = A kind of hex head bolt designed to screw securely into wood) The main goal is to maximize rigidity of the TT mount while isolating from floor vibrations. (very springy 3rd story floor) The four ball studs are designed to support a rigid granite plate shelf which in turn supports the turntable itself. The ball studs thread into coupling nuts where are welded to the interior of the square tubing.
above: A 3D render pre-visualizing the finished assembly. That's a Teres model 135 less tonearm on top of the platform.
Notes: 3D geometry creation in Rhino 2.0, rendering in Povray V3.1 using Moray V3.2 as an interface.
OK so much for "virtual reality".
Here it is. The Reality. This makes a sturdy enough brace for an adult to do gymnastics on. The actual fabrication process went ahead as planned.
To mitigate the frames tendency toward ringing, the internal volumes of the tubes were filled with polyurethane expanding foam. But wait!! Did somebody say --ringing--?
That brings us to the resonant tendencies of this steel frame structure. The rectangular steel tubing, while easy to cut, fixture and weld, is very efficient at transferring structural born resonance. Lag bolted directly into the 2x4 fir studs of the building structure, this frame efficiently transmits any and all vibes traveling up and down the building frame. Noises like bathroom fans, kitchen fans, kitchen appliances, heaters, air conditioners, doors opening and shutting, etc. It all transfers from the building structure into this steel tube frame. Not so good when the ultimate aim is to isolate the turntable from any and all vibrations and resonance, whether it be air born acoustic energy or surface born resonance.
The polyurethane foam, once inserted into the interior volume of the square tubings, did dampen the frame's natural ring tone. This could be observed by gently tapping the frame with another steel object, like a wrench. The ring tone became of shorter duration and of lower loudness. Nonetheless, this framework does ring! With all this in mind, it must be conceded that the above frame, due to its tendency to transmit resonance freely, has a severe design flaw.
Photo #5) I had just received a Neuance shelf from Ken Lyons' company "Greater Ranges". Ken produces these excellent constrained layer isolation shelves and sells them direct. Price is affordable.**
config 1) Neuance shelf directly over the four adjustable supports. (photo 5) The threaded studs with the brass acorn nuts made good supports for this shelf by allowing the shelf to be made exactly level and also to adjust tension just right so that each 'foot' made solid equal contact with the shelf. Background isolation was excellent this way. There was a natural airy sound that, unfortunately, lacked low frequency slam.
Photo #6) Trying the frame with a 3 x 18 x 18 inch granite plate that I sourced from Grizzly industrial. (online catalog at http://www.grizzly.com/ (search the site using keywords "granite plate")) Note that the 4 adjustable supports are not being used. Instead observe the lead pad/large acorn nut arrangement in the photo.
Photo #7). The Teres sitting directly over the Granite.
config 2) Granite plate (3" x 18" x 18") over lead pads that were laid flat over the frame and large acorn nuts as cones. (photos 6 & 7) Big improvement in low frequency slam. Overall sound was quite good, I thought. Maybe there was a bit less background silence compared to the first configuration but the bottom end foundation was more important.
Also, the weight of the granite plate seems to have greatly tamed the frame's tendency to transfer noise from the building structure. After discussion with audio friends it occurred to me that by increasing the load on the frame, I had effectively altered the natural frequency of the assembled load bearing structure to a level that reduced noise transmissions!
Above photos # 8 & 9) placing the Neuance shelf between the granite and Teres. Better yet!
Above photo #10: config as of (2/5/05)
config 3) Neuance shelf directly over the granite plate. (photos 8,9&10) Better still. Background silence gets blacker and quieter but at no apparent cost to low frequency slam. Midrange and high frequencies opened up into a more natural and airy presentation. Subtle details gained improved definition.
Note 1) This wall rack gave a significant sound improvement compared to the previous shelf that I had made from Home Depot triangular brackets and a sheet of plywood. Funny how a more solid foundation beneath the TT also gives a more solid foundation beneath the music it makes. A more coherent, detailed and dynamic presentation was the initial result I heard. But then I began experimenting with two different shelves, pads of 1/2 inch thick lead, brass acorn nuts, etc.
Note 2) Wall mounting represents a compromise made to compensate for the flimsy architecture of the building I'm in. These days it seems as though floors are like springs. Given a more solid floor, I would have preferred a rigid floor mounting. As it is, I can jump up and down next to this turntable without causing nary a quiver. However, building noises and vibrations do travel throughout the buildings structure. If you mount your turntable directly to the wall, preparations must be made to isolate the turntable from this type of structure born resonance.
Note 3) The more solid the foundation beneath the Teres, the more powerful the low frequency slam and kick. This became clear when first trying the granite base on this rack. Big difference..!
Note 4) Increasing the load over the frame results in altering the natural resonant frequency of the load bearing structure. In this case the effect worked to the positive.
Note 5) heavy lead plate, while being dense and able to transmit resonance, appears also to present an effective dampening effect to surface born resonance. I don't mean sheet lead. This is 1/2 inch thick lead plate.
Note 6) photo #10 shows a different platter mounted to the Teres than in the other photos. The lead-shot chambered platter was an upgrade offered by "Teres Audio" through an exchange program.
** Greater Ranges, currently is not selling the Neuance Platform Shelves at this time. Hopefully, if enough of us can talk Ken back into it, he might change his mind and begin production again.