Turntable rack design

Re: Turntable rack design

Postby Pevo » Sat Oct 07, 2017 8:17 am

Edw, did you make the rack in your photo? Very nice! I‘ve been thinking of building one of these, but was a little unsure of the size of the extruded material. Hopefully you can give me a little guidance on this. Most of the examples I’ve seen appear to use a size material larger than what I could find, i.e., the largest material is 1.5” x 1.5” (or 40 mm x 40 mm), yet the images look like the material is at least 2” x 2”. What size did you use? How did you support the butcher block within the rack? Lastly, does the material tend to ring at all? I can think of ways to damp it, but wasn’t sure if that is even a problem. Thanks in advance!
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Re: Turntable rack design

Postby edw » Sat Oct 07, 2017 5:38 pm

Pevo:

Yes, I built the rack in my photo. The 80/20 consultants were of great help on the telephone in getting my hand drawings to a working build. Most people use the 1.5" thickness aluminum. I did too. There are a lot 1.5" variations now than when I built mine over 10 years ago.

The first thing was finding some maple blocks that weren't custom made or from the audioshops, which all have ultra high markup. I went with Boos blocks made for the kitchen - one of the early adopters. At that time, they came standard 20" x 15", which was wide enough for the 19" wide rack mounts and also just long enough for the length of my amps (although the rear handles stick out in the back a bit). I got a good price on a dozen at a local chef outlet.

I used the #1502LS and #1503LS 1.5" aluminum beams. The butcher blocks are nestled inside the rack with 1/4" spacing all around the butcher block so it does not touch the aluminum beams. The butcher blocks are suspended by Z-brackets (#2434) that bolt to the underneath of horizontal aluminum beams (2 on the left, 2 on the right). Between the Z-brackets and the butcher blocks I used small rubber/composite blocks for isolation. More for the turntable platform, and that is why that butcher block rides a bit higher than the others in the photo.

The main discussion I had with the consultant was whether 4 of the Z-brackets would be strong enough to hold the amps at 100 lbs or more (a problem with long length butcher blocks as they would buckle unless several inches thick). 80/20 ran some simulations with the Z-brackets and said I was within the margin of safety. They have held up nicely over all these years.

If you hold the 80/20 aluminum beams and tap them, they do ring but not for a long length of time. But when assembled and weighed down, they don't ring, just get a thud that's higher in pitch given the medium. I know some use a little sound absorbing materials in between the beams but given the mass on my rack, it has been a non-issue, even with a sub. But ultimately, it depends on the strength of the rack build itself. The stronger/tighter/shorter, the less likely it will ring. That's one of the reasons I went with shorter butcher blocks and shorter aluminum beams (plus, it also isolates each component from the other somewhat). Downside is that it also increased the number of aluminum beams and hence the cost. But it is very modular and adjustable.

[Sorry for the long response; now back to the original thread].
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Re: Turntable rack design

Postby Pevo » Sat Oct 07, 2017 7:57 pm

Thanks edw, that’s exactly what I needed to know!
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Re: Turntable rack design

Postby JohnCh » Wed Dec 06, 2017 11:52 pm

Revisiting this as I'm finally getting around to making the rack and have another question about construction. It will be all Maple with 3 shelves and 2-3/4" x 3" legs. The lower 2 shelves are 19" x 55" x 2" and the top shelf is 20" x 61" x 2-1/4". The legs attach to the sides of the two lower shelves like the Timbernation racks, and the larger top shelf will sit on top of the legs (like a table). With this design, am I better off rigidly attaching the top shelf to the legs, or decoupling it via cones? The top shelf will weigh about 65 pounds, and the Classic Sig will double that, so there is a lot of mass. Is there a sonic advantage to either approach?

Thanks,
John
VPI Classic Signature, VAS Nova Signature, CIAudio PEQ1 MKII w/AC15 MKII power supply, Oppo BDP-105, ModWright SWL 9.0 Anniversary Edition, CIAudio E200S, Magnepan 1.7i w/Mye stands, REL Strata III
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