[firewall]

I have a 1" thick 18x18 slab of birch on top of a marble base.

Each level is isolated.

The BioTracer takes care of the rest.

I can crank the subwoofers up to 118+ dB 17-120 Hz and there's no noticeable pickup/resonance now that I added the birch.

What do you use for sound isolation?

[Bob2]

65 lbs. of 6061 billet aluminum. Seems to work quite splendidly. Especially since it sits on 100 lbs of lab grade granite surface plate.

[Craig B]

Black Diamond Racing carbon fiber pucks and motor platform.

[BobM]

The shelves on my stand are actually seismic sinks with 50lbs of sand in each shelf. A maple board floats on top of the sand. But that's not enough for the turntable. It's plenty of mass but doesn't completely isolate it. So I sandwich another maple board on top of that and separate the two boards with a bunch of squash balls, kind of like a Ginko isolation device. I find that the rubbery isolation coupled with the mass it all sits on does the job nicely.

Here's a test. Put the tonearm down on a record but don't spin the platter. Now tap your knuckle on your shelf and see if you can hear that thump through your speakers. If you can, then you don't have enough or proper isolation. Yeah, this is an exceedingly difficult test to pass so don't be surprised when you hear that knuckle rap quite plainly.

[dpatters]

Maple platform from Mapleshade sitting on IsoAcoustics Iso-Pucks.



Don P

[RonP]

Maple platform from Mapleshade sitting on IsoAcoustics Iso-Pucks.



Don P

I have a similar arrangement. I have platform from ButchersBlock Acoustices with 4 x GAIA II feet I added. The feet made a big difference.

[sunnydaze]

I site both my tables on a maple butcher block platform with these underneath:

https://www.supplyhouse.com/DiversiTech-MP-2E-EVA-Anti-Vibration-Pad-2-x-2-x-7-8

Simple.  Effective.  Cheap!  Passes Fremer's knuckle rap test (as described by BobM above) with flying colors.   

[sanlanman]

The Ikea Bamboo cutting boards on the round iso pads work pretty good for me.

[dlaloum]

Start at the bottom.... a substantial concrete paver with heavy duty sorbothane feet/pads 60cm x 60cm (2ft sqr)

Cheap and high mass/inertia ...

Then Ikea Lack side tables - this is the opposite, they are ultra light - they happen to be perfect rack width and depth (55cm x 55cm)

Their paper/veneer construction is also perfect for absorbing higher frequency resonances - Two, of these one on top of the other, and a third using just the table top as a base....
You can screw/bolt them together, or you can judiciously use sorbothan feet between some of the layers

For stability - best to only use the sorbothane if you have sufficient mass above.

Measuring the resonance frequency at the TT is critical - you need to record some tracks making sure you catch the 5hz to 20hz range - and walk around the room, stopping periodically - you should be able to see the footfall resonance (and any other major resonances).

Once you know their frequency, you can adjust by using absorbers (sorbothan, magnets, whatever) and or mass to absorb and adjust (usually lower) the frequency of the resonance to where it does the least harm...

You may not need a platform, if your entire rack is effectively an isolating platform!

A heavy power amp at the bottom level helps too...

[lazydays]

I come from an industry that is very paranoid about vibration in a static position (what you call feedback).

* the OP showed what he used. If it works then so be it. That thin slab of granite composite is going to flex all over the place, and should be three times thicker at the minimum. I recommend what is known as a bench top surface plate (about 1.5" to 2" thick) made of black granite composite on the bottom. Set it on three points and never four or more (physics says you can not level a four point plane.) Yet three is known as perfect. Of course if you got deep pockets you might try an inch and a half thick piece of Mallory Metal ($$$). It is almost a perfect anti vibration mat. Won't rust, and is pretty damned heavy. Never use a slab of solid cut granite unless it is a grey color with no white lines running thru it. All premium surface plates are made of a granite composite that is ground down and glued together. Also softer than regular granite I might add here. Still if a surface plate is your thing then just buy a tool room grade and look under it for the rubber pads. Mark their location and get rid of them. A tool room grade is almost half the price and the only difference is the actual surface quality (a Lab grade spec is 1/2 arc second per foot where as a tool room grade will be about .000075" per foot. The turntable will never know the difference! Honestly a 2" thick concrete slab will work just as well, and maybe better.

If you have a friend that is a welder than fabricate an aluminum box with an open top. (whatever size pleases you) Cut another aluminum plate about 1/2" thick or even 3/4" thick. Level the box as close as you can, and mix a bunch of grout (like your bathroom tile uses). Fill the box till the top plate is just above the outter walls. Let is set for a week. Go to Walmart and buy some spray cans of primer. Then paint the box. The top plate should lack a quarter inch from touching the side walls all the way around. Vibrations and grout don't like each other, and that's why a lot of extreme precision equipment has grout under the jacks to level it. There is an epoxy that's even better, but can't remember the brand name. Plus it only comes in three gallon pales. ($$$)

I had access to vibration analyzing equipment, and did check my turntables with it. I found the tone arm to be a perfect antenna. The issue is also in the mount. Here something like solid copper or Mallory Metal is the best. Wood is bad on a good day. No matter how good of a job you do in blocking the feed back your gonna always have either a 60Hz or 50Hz feed back due to your house current. There is a fix for that, but it's also half the price of a new Corvette! The turntable motor is almost always of cheap quality. On one of my tables I could tell you how many balls were in the ball bearings! Ball bearings are creators of feed back! So you gotta live with that of course. Then there is the thrust bearing. I swapped mine out for a grade ten ceramic ball bearing, and saw the difference on the meters. I use GN Paste for the thrust bearings and a good lube oil for the rest. The best place to start is the isolation stand and then the motor mount or whatever holds it
gary

[lazydays]

I site both my tables on a maple butcher block platform with these underneath:

https://www.supplyhouse.com/DiversiTech-MP-2E-EVA-Anti-Vibration-Pad-2-x-2-x-7-8

Simple.  Effective.  Cheap!  Passes Fremer's knuckle rap test (as described by BobM above) with flying colors.   

The pads you are using to isolate the feedback came from a company called Machinery Mounts in Columbus Indiana. The normally come in four inch squares, but have bought six inch ones from them (less than four dollars a piece). I used to buy them by the pick up truck load. Have seen the adds on Ebay where the guy is selling one for what he paid for the bigger piece. It cuts well with a saw. Comes in several different weight ranges, and I'd think the lightest would work well. I made this post to help you save some beer money!

There is another system out there that uses air bladders running off a small pump (aquarium?). It will always be level, and has almost zero feed back thru it (your still going to pick up the dreaded 60Hz).
gary

[sunnydaze]

No idea about the technical aspects of these pads.     I don't care.  I just try stuff, and try not to overthink it.  It either works or it doesn't.

My tables don't skip even if I do jumping jacks in front of them, there is no airborne feedback, and they pass the knuckle rap test, so I'm happy.  It helps that one of my tables (Townsend Rock mk3)  has an air bladder built into it. 

The website / seller I linked earlier does have them in different sizes and materials, as you mention.

https://www.supplyhouse.com/Pads-11752000

Even though they are not necessarily designed for audio use, the reviews show that many guys successfully use them for that purpose.

[lazydays]

No idea about the technical aspects of these pads.     I don't care.  I just try stuff, and try not to overthink it.  It either works or it doesn't.

My tables don't skip even if I do jumping jacks in front of them, there is no airborne feedback, and they pass the knuckle rap test, so I'm happy.  It helps that one of my tables (Townsend Rock mk3)  has an air bladder built into it. 

The website / seller I linked earlier does have them in different sizes and materials, as you mention.

https://www.supplyhouse.com/Pads-11752000

Even though they are not necessarily designed for audio use, the reviews show that many guys successfully use them for that purpose.

those pads will help you, yet all I was offering was a direct source. The guy on Ebay is ripping people off. Then I said something about the weight factor. They sell different ones for different weight placed on them. Some people have a lot of mass in their setups and some don't.
glt

[sunnydaze]

those pads will help you, yet all I was offering was a direct source. The guy on Ebay is ripping people off. Then I said something about the weight factor. They sell different ones for different weight placed on them. Some people have a lot of mass in their setups and some don't.
glt

Agree with you 100% on the tweak rip-off artists.  Plenty of guys selling these online for jacked-up prices (including Amazon) not just that guy.  Mapleshade Audio has the cork ones jacked-up at more than 20X the price.  Disgraceful!

https://shop.mapleshadestore.com/Mapleshade-Isoblock-Sets_p_1224.html

I bought mine several years ago from that vendor I linked.  Don't remember the exact count but I bought an entire box of 30 or so, and they were super cheap on a per unit basis. (I don't see the bulk boxes on the website anymore).

I'm actually not sure how much these pads are helping.  I think a big part of the resonance control is that my DIY rack is very solid / heavy / rigid, made with maple butcher block and 80-20 extruded aluminum.  My avatar shows it, and other photos in my Gallery if interested.

[rotarius]

Every audiophile worth a damn knows to use metal or carbon cones for vibration control.  Add a jar of machine dynamica pebbles behind the listening position for maximum effect. The idea is to employ quantum resonance schema to neutralize the system resonances. Perfect for turntables.

[firewall]

Rotarius:

"Every audiophile worth a damn knows to use metal or carbon cones for vibration control.  Add a jar of machine dynamica pebbles behind the listening position for maximum effect. The idea is to employ quantum resonance schema to neutralize the system resonances. Perfect for turntables."

Were you just drinking, or also imbibing PCP when you created this brilliant & unique manifesto?

I think it was the latter...

IN any event, cheers!

[lazydays]

Rotarius:

"Every audiophile worth a damn knows to use metal or carbon cones for vibration control.  Add a jar of machine dynamica pebbles behind the listening position for maximum effect. The idea is to employ quantum resonance schema to neutralize the system resonances. Perfect for turntables."

Were you just drinking, or also imbibing PCP when you created this brilliant & unique manifesto?

I think it was the latter...

IN any event, cheers!

Goto the half priced book store and get a good book on Physics (second and third semester) and Applied Mechanics. You'll get a good lesson or two. There are a few others, but the last book is the one to start with
glt

[lazydays]

The shelves on my stand are actually seismic sinks with 50lbs of sand in each shelf. A maple board floats on top of the sand. But that's not enough for the turntable. It's plenty of mass but doesn't completely isolate it. So I sandwich another maple board on top of that and separate the two boards with a bunch of squash balls, kind of like a Ginko isolation device. I find that the rubbery isolation coupled with the mass it all sits on does the job nicely.

Here's a test. Put the tonearm down on a record but don't spin the platter. Now tap your knuckle on your shelf and see if you can hear that thump through your speakers. If you can, then you don't have enough or proper isolation. Yeah, this is an exceedingly difficult test to pass so don't be surprised when you hear that knuckle rap quite plainly.

Bob;

I honestly like the way you did things for starters. Good thought process. I once built three leveling pads that used light oil (Mobil DTE21 or DTE20 to be exact) as a dampening device. The three were tied together with 5/32 diameter tubing. (getting the air out of the lines took some doing). They were roughly 2.000" diameter pistons riding on oil. I should have made six, but only did three. The fit was very tight between the piston and the cylinder (perhaps .001" or slightly less. They sat at my house for a year or so waiting for me to get off my butt and install them as an experiment. Along comes me brother inlaw, and he takes them home with him to put under an SL1200. Fast forward thirty plus years and Larry is still using them, while I didn't bother to build another set with even better seals. I told Larry he wouldn't have to level the table as it would level itself once all the air pockets were gone. Did they work? All too well as they never came back. He swears by them to this very day
gary

[lazydays]

Agree with you 100% on the tweak rip-off artists.  Plenty of guys selling these online for jacked-up prices (including Amazon) not just that guy.  Mapleshade Audio has the cork ones jacked-up at more than 20X the price.  Disgraceful!

https://shop.mapleshadestore.com/Mapleshade-Isoblock-Sets_p_1224.html

I bought mine several years ago from that vendor I linked.  Don't remember the exact count but I bought an entire box of 30 or so, and they were super cheap on a per unit basis. (I don't see the bulk boxes on the website anymore).

I'm actually not sure how much these pads are helping.  I think a big part of the resonance control is that my DIY rack is very solid / heavy / rigid, made with maple butcher block and 80-20 extruded aluminum.  My avatar shows it, and other photos in my Gallery if interested.

years ago I had access to one of the most sought after mechanical CAD programs on the planet. Never used it a lot, but when I needed it, it was a God send. I could induce various forms of movement (vibration, twist , etc) to it to see what it would do without ever building it. I built one using copper tubing (2" x 4") that was capped off at the ends and filled with sand. The vertical legs were seamless mild steel tubing (actually hydraulic tubing) that met an annealed spec. It was a triangle system that literally weighed about forty pounds minus the copper bars. (I used copper because it doesn't vibrate). It would have done well without the sand, but was far better filled with washed playground sand. I had pads welded to the bottom and top of the upright posts for leveling and removable plugs on top to fill them. Then along came something called the Lead Balloon and the Copper balloon in a similar design concept. I put it aside and ordered in the copper one. Still waiting on it! My welder passed away, and as far as I know the parts are still in his old shop. All the parts I used came out of a junk yard except for the copper bars. Probably less than fifty dollars in material.
always experimenting
gary

[qdrone]

Bright Star Audio Sandbox filled with Kitty Litter and a 25lb. weight lifting weight under my turntable.