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I abstracted the following from a whitepaper (link) published by Ametek/TMC, a big vibration control equipment manufacturer. It's a good description of what you need to do to really isolate a turntable from FLOOR vibration. Floor vibration in my experience typically has a source frequency around 5 Hz, more-or-less. My little project was undertaken to reduce structure-borne vibration arising from airborne sound exciting the relatively "lively" steel furniture my TT was sitting on. I feel it got some results in that area. However, their graph, which appears to me technically correct, suggests the vibration isolation for my project is effective only in the audio range, above 40-50 Hz in fact. That seems useful, nonetheless, seeing that I don't discern any amplification of floor vibration.
Extrapolating the idea, however, lightweight platforms on relatively stiff foam pads would be effective for isolation at even higher audio frequencies, curtailing their benefit.
From TMC: "Homemade [vibration] isolation systems - often a steel or granite slab placed on rubber pads, tennis balls, or air bladders - will work only if the disturbing vibrations are high frequency and minimal isolation is required. While all isolators use the principle of placing a mass on a damped spring, their performance is differentiated primarily by spring stiffness: the stiffer the spring, the higher the resonant frequency. Thus, homemade solutions are limited by their high resonant frequency.
"A tennis ball under a steel plate [or granite slab] with a 7 Hz resonant frequency begins to isolate above 10 Hz and reduces vibrations by 90% at 30 Hz. But most building floors exhibit their highest vibrational displacements between 5 and 30 Hz, so that a tennis ball or rubber pad actually makes the problem worse by amplifying ambient frequencies between 5 and 10 Hz.
"[By contrast, a pneumatic] piston isolator with a 1.5 Hz vertical resonant frequency begins to isolate at 2 Hz and can reduce vibration by over 95% at 10 Hz." This refers to the superb gas-piston isolation tables these dudes manufacture for things like electron-microscopes.
If you want to get serious about vibration isolation, this company's platforms and similar ones come up for sale on eBay under the industrial category for pennies in the dollar, if you can own a forklift- they run a few hundred lbs!
Follow Ups:
I've read your post and the replies to this point.
There's a couple of thing going on here, and they are different issues. One is air-borne vibration, and the other is structure-borne vibration.
Mass and stiffness is your friend with regard to air-borne vibration (sound). The typically very small amount of air-borne vibration isn't enough to cause a massive wall or floor to propagate a significant amount of sound through it to another location.
On the other hand, even a massive and stiff structure will READILY transmit vibration when it is "struck" or otherwise set into motion. This is when "isolation" approaches such as mounts become important, in order to absorb the motion before it gets to a place where we don't want it.
A third situation exists with room resonance. You may have observed that a car, truck or other sound source produces a noticeable resonance in a room, but, outside, it's not as loud. This is a result of the structure and its enclosed air volume sympathetically vibrating due to sound either via the air or the ground.
As I've been recommending for several years, "Master Handbook of Acoustics" and "Music, Physics and Engineering" is required reading for all audiophiles.
:)
Which is why the two turntables in my second system, which sits on the poured concrete floor of my basement, which in turn sits on solid earth, are so clean sounding. Because of the concrete base, there is not much effort required to isolate the turntables. No fancy stands or shelving need apply. They're sitting on an old but very solid wood dining room side table on dense cork or styrofoam like pads that are used to pack heavy but delicate instruments for shipping. (Someone at a warehouse gave them to me for free, years ago.) I've got those square pads shown in your photo, and I do use them, but I cannot hear any difference with or without them.
...experience agreeing with theory! Those little Mapleshade-style pads I'd expect to be useful only in the audio frequency range when loaded with ordinary turntable-size masses.
My best system is in my basement, also. Poured concrete floor, turntables sit on a custom wood stand and I also have granite counter-top underneath the turntables. Zero issues with vibration.
Thomas
"In a democracy, uneducated voters get the leaders they deserve."
Concrete doesn't isolate anything sitting it from floor borne vibrations throughout the audio band.
Well, you can jump up-and-down in front of my turntable and it doesn't miss a beat. Perhaps the advantage of concrete is that it attaches my turntable securely to the earth, which doesn't seem to vibrate very much where I live. I can't even get the earth to to vibrate by jumping up-and-down. YMMV
Good luck,
John Elison
The main fact in my case is that the concrete slab is on solid earth. However, I would think that concrete per se is not so bad because its porosity should help to dissipate energy as heat. I am prepared to be proven wrong, however.
Exactly as above.. My Thorens, which has for 35 years lived in my concrete floor slab/carpeted Listening room.
Had Zero vibration/resonance issues.
However it exhibited foot fall issues when relocated to the 3rd floor of my house.
It went back down to the main system .. quickly.
I enjoyed that, thanks.
I had never gone the tennis ball route, preferring, as instructed, halves of sponge rubber multi color balls, the kind that are now not around often, they have been replaced by high compression "super balls".
I had no method beyond following suggestions, and don't know if sonic improvement was ever achieved, but it felt like I was in the game. My system didn't have a real high level of resolution.
When it comes to isolation, I am glad I have a suspension turntable. I still have to be aware of the platform for optimum performance, but thank goodness I am not starting from scratch and had an audio engineer take a crack at the isolation situation before it became, solely, up to me.
I also have a couple of marble slabs to use in a mass loading situation, but I have mine only because the local department store was selling off the marble counter stones, used for candy making, I believe. I just figured they would be better than nothing.
Then , of course, in reading about marble , I came across almost the entire population of the earth saying it was only slightly better than tin sheeting set on springs for turntable isolation . So I added a typewriter isolation mat to the mix.
I bought a solid looking garage storage shelf to hang on the wall, and put the table and stones on that. (Note: if you are looking for nice looking shelves for a turntable without paying for audio furniture, forget it. Everything is bookshelf. THat's why Mr. Cheap here has garage shelves for audio furniture. )
However, you strike me as a guy that can figure a way to put those marble slabs to better purpose, and I would be interested in that..
I have used red brick for speaker stands, and stacks of red wood 4x4's for the amp and turntable supports, selected for mass and portability , and would be interested in any good sonic strategies.
I've been noodling on this a few years......35 or so, as a structural and manufacturing engineer, and there are a few ideas that seem basic.
Isolating floor vibration: Mass is a good idea- like the mass of a heavy slab. But that mass has to be suspended on soft, flexible springs. By soft I mean the mass must result in substantial deflection of the springs, like a couple inches! That much deflection is needed to give you a very low resonant frequency, which needs to be low to result in isolation from floor vibrations.
Floor vibrations seems to center around 5Hz or so. To get any degree of isolation requires the mass-spring isolator have a resonant frequency below say 3Hz. For the curious, the resonant frequency Fn = (1/2*pi)*sqrt(g/deflection),, where g= acceleration of gravity (386 in/sec.sec). Use consistent units.
One commercial HiFi product that applied this principal effectively was VPI's aftermarket plinths for the Denon DP-75/80 turntables. The oak base section housed a 50-lb. (!) steel/plastic laminated slab on big springs that I measured deflection of around 2". Worked!
There are the airborne sources of vibration to consider, but they're a unicorn of a different color. You have several ways the soundfield in your room affects the turntable:
One aspect of airborne pickup is direct excitation of the components of the table or the surface of the LP. Dustcovers seem to be a good source to pick up airborne sound, as do light shelves. How this affects your particular turntable is highly variable ns depends on the isolation features of the table: suspensions, feet, etc) and the will of the gods.
The result of airborne pickup is generation of "surface acoustic waves" (Rayleigh Vibration) in the plinth, platter and LP. This touches on elastodynamics and is beyond the comprehension of all but about 13 Americans getting PHDs, but the idea is that a surface excited by sound pressure responds with waves in the solid medium. A simplified analogy is if you've ever stood next to a snare drum (not being played) when the orchestra is loud- the drum will respond and you hear the snares rattle. When this occurs in your turntable it's a bad thing. These waves bounce around, resonate, get polarized (Love's Waves) and may get to the cartridge. The energy is stored to a degree that relates to the depth and internal damping of the surface being bombarded. That's why you see turntables with heavy stone-like material for the plinth- it "sinks" SAWs, reducing pickup by the cart.
These effects are subtle and hard to trace. Some of the resonances add "euphonic" colorations and may become quite likeable. I think of them as friends... The nuclear option to avoid airborne vibration would be to put your speakers in another room, with the turntable preferably in the basement! An 'appeal to extremes...' eh?
Thanks for the reply.
I once used the nuclear opinion you mentioned, speakers in front room, turntable and amp in another. Not super handy, but the kenwood table I used at the time would howl at the sound levels some enjoyed, so a solution was found. It had a resin mixed with stone powder base, but the suspension was up to you. It was replaced, and easily bettered.
I don't have the technical chops to do a lot of productive explorations, unless you want to count on random experiments and dumb luck for your results. So I play follow the leader, reading and selecting methods that seem reasonable. Vibrations and waveform understandings are interesting to me.
I saw the slabs pictured, and thought I should mention I also had some , in case you had attempted to used them in turntable supports.
IN reading, folks say the material, marble, excites too easily, and since you are a guy with resonant frequency equations easily at hand, I figured you might have a successful way to use them . I suppose I could weigh them and figure with the math you provided. PRobably won't happen , the spring deflection would be hard to control, for a DIY result that wouldn't need a lab coat and tongs to play a record.
I once read a story by an audio reviewer, who, in seeking a quit place to listen to music, thought he had found the answer. An old english cottage built over a giant rock, the exposed portion was exploited to use as ledge and hearthstone for the fireplace. He figured the buried rock was at least fifty tons , probably more. The perfect mass isolation platform for his turntable. All he was looking for was a quiet electrical situation out in the country, and figured he got really lucky. Until he bought the place and found that a local rock quarry used the country road, but only at night, so people aren't troubled. The big rock picked up the rumble from the road a mlle and a half away and microphoned it right into his turntable. The guy didn't have many options, this was back in the fifties, hi fi was new, he was building the hobby. .
When you eliminate vibration from vinyl playback, the improvement is quite noticeable and very desirable. My most recent vinyl recordings have been made using 5.6-MHz DSD, which is exceedingly accurate and transparent. I monitor my recording sessions with headphones so my speakers remain off. This pretty much eliminates acoustic and mechanical feedback from the recordings. Then, when I play the recordings at high volume through my speakers, the sound quality is awesome. The music sounds noticeably cleaner than playing vinyl directly at high volume.
Best regards,
John Elison
That does seem like the best electrical strategy to fight vibration in playback, separate the signal generators from external excitement. Pretty cool , and clean.
Myself , I would have just grabbed another record and listened to twice as much stuff in the same time. Once the music starts, I have a high tolerance for added dreck , a trick my mind is used too, , having grown up with a consul changer in the front room , full of 78's and the playback needle that god gave you, why would you ever need to get a new one? Plus, it could flip over to 33 1/3.
Your first statement about vibration in vinyl is so very true, and hit me hard when I got a quieter table. All of a sudden stuff was flying around the room with some rock records I had owned from adolescence . The soundstage was an entirely different illusion, going from speakers are not evident , to, I can listen to directions in the hall, if an instrumental section or solo catches my attention.
Makes it easy to understand why there is a market for super turntables the size of an arm chair, with cost like scientific equipment. Not that I would ever need or want one, but I can see the game from my cheap seats, finally, as I assembled stuff over time.
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