And that brings us around to clarifying what is really meant by "isolation", and what purpose it serves. To my mind, there are two treatments that turntables may need: 1. Isolation - minimizing the impact of automobile traffic, footfalls, countertop bumps, construction work, which are low frequency, reflecting the low frequency resonances of floor or structure, or from vibrations carried through the earth. This needs mass in combination with some actual low compliance isolation with a low resonant frequency - think hanging your turntable by bungee cords. 2. Dampening - reducing the high-frequency resonances of the turntable materials or mechanical parts (excited by the music on vinyl), or other vibrations from rack equipment, by employing coupled energy-dissipating materials. Reducing the ping your platter makes when you strike it, or the hum of a transformer. Think packing your turntable full of clay or butyl rubber. The first, isolation, is a concern for transient events that don't necessary affect your sound, but protect your subs from fluttering, your amp from exhaustion, and your record from skipping. This is an issue for all turntable owners, protecting you from "real" problems. The latter, dampening, however, is more in the voodoo area, with the goal of improving the sound quality. Some here may call a turntable that doesn't exhibit these symptoms "dead" or "overdamped", whereas I would prefer to get only the original sound cut into the groove. The cutting board as mentioned in this thread would only apply to this category, but better would be just a same size slab of rubber. If you divide your "isolation solution" into these two categories, you'll see that random happenstance may not be the best solution. Does it add the most mass to lower the isolation low-pass frequency or impact of vibrations? Does it add significantly more isolation so the turntable doesn't move from external shakes? Does it deaden self-generated turntable resonances? If it isn't the best material for either isolation or dampening, it may just be wishful thinking. Rather, just a well-made turntable, like a Technics 1200 with a plinth of damping material and squishy rubber feet, may suffice.
We're in the realm of the sandwich approach so the inner tube will remove low frequencies and then a board removes others. I had the pleasure of listening to the Kronas Sparta turntable, £124,000, and if I remember rightly it's structure employs the sandwich approach different layers filtering out different frequencies.
I agree with most things but "Voodoo" I'm not sure. Random is what I was saying don't just trust me if I say Bamboo, it's a option to try, which can work but given your circumstances Maple may be better. You can have hours of fun, being a very sad person, as you compare different approaches, to see what works for your situation.
Concerning the Ikea Lack tables (same material as their Kallax and Expedit range): hold your ear on the table/rack and knock it with your hand. To my ears they ring/resonate like hell, sounds like a hollow chamber. Which what it is actually (honeycomb hollow structure). They may be stiff, lightweight and strong but imho they do resonate.
First table I used for my LP12 was a IKEA Lack, back then it was MDF, perhaps an antique out there(?).
Any structure at all resonates at characteristic frequencies related to the speed of sound in the structure and its density. The only thing that changes is how well the structure is damped. Aluminium plate really rings if suspended and struck. Honeycomb structures don't - they are well damped. And have resonance frequences which are higher than a solid with the same structure. Which is why they are used in spacecraft construction to survive the launch vibration, and then 1000g shocks when explosive bolts fire to jettison parts of the structure - like rocket stages and the fairing. This is part of the BepiColombo Mercury mission vibration test last year. That is 7 tons of assembly being shaken. Launched successfully on 20th October with one of my instruments on board (the Mercury Imaging X-Ray Spectrometer). Fast forward to 35 minutes in to watch it go BepiColombo launch replay Lots and lots and lots of honeycomb on that! PS the other very well damped material is Panzerholz The Virtues of Panzerholz : An Investigation into the Acoustical Properties of Aluminum and Panzerholz and has to be a contender for audio shelf and rack construction. Indeed turntable main structural elements have been made from Panzerholz.
That's very interesting, purely out of interest I tried but I couldn't find the price of this stuff, I'm guessing not cheap. And I thought my Aluminum casing was good
My TT is sitting on a piece of B25 Panzerholz 25" x 20" x 1". This was from the UK supplier of the stuff. That cost me about UKP100. It is made by a German company called Deglinit Startseite - Delignit AG . Panzerholz means Armoured Wood, and some grades are bulletproof. I bought from L T Lewis Delignit sole Distributer Pinblock, Beech Plywood, Outrigger pads, Plinths, beech multiplex,compressed wood, del;ignit, delignit panzerholz,beech plywood importers, Delignit beech plywood who were very helpful. The piece I have was an offcut they had which was pretty much the right size I needed.
Honeycomb core sandwich materials are not "damped". They are instead quite rigid in multiple dimensions for their weight. I've held aerospace aluminum 1" honeycomb material, and it is the opposite of either damping or isolation - it is a better choice if you want your forces or vibrations to travel through a material unmitigated.
Given that any material at all has bending resonances, the only things that you can change are (a) the frequency of the resonances and (b) the Q of the resonances. Q value really means for how long it "rings". High Q means it rings for a long time - a bell is a good example of a very high Q by design. So what are the best placed resonances for audio applications? I would suggest as high as possible for turntable use. Because of the RIAA boost of 20dB at the lowest audio frequency, a turntable is very sensitive to anything that resonates at frequencies less than say 200Hz. That is a tall order, but honeycomb structures can achieve that depending on the construction. The other parameter is the Q, and clearly the lower the Q the better. You need a material that goes thunk when you rap it with your knuckle and not ting. Now I happen to have two carbon fibre skin honeycomb shelves with spikes underneath. These were bought thirty years ago and made by a long defunct audio company, I'd have to take some gear off one to read the name. And they very definitely go thunk. Wooden honeycomb such as Torlyte also goes thunk, I suspect because of the internal frictional losses in wood. The link I provided regarding Panzerholz as compared to aluminium shows that Panzerholz also has the low Q property too. And that is also why multi-layer construction works. Either discrete layers with some damping between them (as some on this list use), or constrained layer construction like the (long discontinued) Rockport Sirius, an insanely expensive device when it was made Rockport Technologies System III Sirius turntable and tonearm and the epitome of low resonance construction taken to the absolute limit.
Because granite is not anything other than a rigid flat surface and not a damping or coupling substance. It MAY depend on your table, but everything I've read by the experienced (with Thorens suspended and non-suspended TD-124 idlers) emphatically state don't do it. Instead, slate is highly recommended. Regarding Lack: Hey, if they work for you, great. I've tried all of my components, one by one, on the Lack tables, and they all sounded worse. I have carpet, and the Lack would wobble a bit. Maybe spikes under the table's feet would have helped? The Expedit shelves, however, were pretty decent. Heavy, filled with records and not wobbly.
You have taken my initial post either out of context and/or misconstrued what I was saying. I did not suggest using only granite. I said to use slabs of granite separated by sheets of rubber, in order to give a series of (significant) density changes which will give an extremely effective dampening system for preventing vibrations from being transmitted through the stand / shelf (etc.) on which your turntable is placed, to the turntable. Those vibrations can come from the floor on which the stand sits (or wall to which a shelf is attached) or the from vibrations of the stand itself, both caused by the output (airborne or transmitted through the floor) from your speakers. (And I specifically said that it will not help gross effects like someone walking on a very springy floor on which the stand sits.) Given its high density, granite is an excellent material to use in this case, (as are the sheets of rubber that I described,given their low density, and other properties like non-slip) and rejecting it as such makes no sense, at least not in any sense that's based on sound engineering or fact. Of course the turntable itself, sitting on that stack of granite / rubber, needs to have its own inherent capability to deal with the direct effects of any airborne energy (ie. sound waves). Jeff B. Eng. (Mechanical)
You're right it's only £27,000 with tonearm, perhaps my gasp distorted the price but I think I'm right about the plinth being a sandwich design.
It's obvious that my understanding comes from Isolation For Dummies, in fact I became interested in this due to a old thread, possibly started by Barry Diamant. If I recall correctly he preferred Marble over Granite as Marble didn't 'ring' as much and this was from trying both options.
I forgot to say that I did try a Granite chopping board, which was replaced and bettered by the Bamboo board
When considering two masses isolated by a resilient layer, the resonant frequency is only determined by the extension (or compression) of the resilient layer. So if the rubber layer between the granite slabs compresses by 0.1mm (under the weight of the granite), the resonant frequency is 1/2pi x root (1/10^-4) since there are 10^4 0.1mm in 1 metre. Of for a compression of delta, resonant frequency is 1/2pi root (1/delta) So in that case the resonant frequency is 16Hz. So below 16Hz the slabs tend to move as a single unit (and transmit the vibration) and much above 16Hz the combination with reduce the vibration by 12dB for every doubling of frequency. Now since it is a square root behaviour, you have to work quite hard to get the resonant frequency much different to that. To reduce the frequency to 1Hz, the compression of the resilient layer would have to be 25mm (about an inch). That means that you can easily work out what the effectiveness of your vibration isolation system is. Measure the thickness of your chosen resilient layer. Now sandwich it between the slabs of whatever and measure the thickness now. Since the compression is likely to be quite small, you'll have to use digital calipers or some such to make the measurements.
My method is try and see, I've just placed two pieces of a camping roll mat as the base, so it goes roll mat Bamboo board, inner tube Bamboo board. I'm not sure if it makes much of a difference, well it doesn't make a significant difference. My question would it be better to place the camping roll mat between the the two boards, I'm auditioned out at the moment. And obviously a foam camping roll mat is not rubber, it's just what I had to hand.
So if I am reading this correctly, for the resilient component you would want a layer of highly compliant/compressive material like gel/jello or maybe sponge (soft foam, memory foam?) to get the resonant frequency down to 1hz and minimize the ability of the individual layers to act as a single unit in the audible range?
Granite vibrates and 'sings' because of its hardness and offers no isolation from vibrations. It may look great but it has little or no value as an isolation platform.
I use a marble slab resting on sorbothane feet between my TT and the rack. Really focused the sound and improved the bass. The rack itself is spiked through carpet on concrete basement floor.
There is a slight gotcha. The material needs to be linear for the simple equation to work. In other words halve the weight and the compression halves. Double the weight and the compression doubles. A really thick layer of closed cell foam might work - that started off at maybe 10cm thick and compressed to 7.5cm under the weight of the granite/slate/concrete etc. Those numbers are just off the top of my head, but it will be something of those sort of dimensions. I found out about this "it is only the extension of the spring that matters" from I guy I worked with twenty-odd years ago. I was figuring out the natural resonant frequency of a complex bit of mechanics suspended from a network of springs. So I am working out the weight and looking at the spring specification. And this guy looks at me and says "only the extension of the spring matters". I had to write it all out until it became blindingly obvious. The rationale is if you have a heavy weight and a stiff spring the mechanics is identical if you have a light weight and a weak spring - the only thing that sets the frequency is the ratio of weight to spring constant. And that boils down to the frequency only depending on how much the spring stretches.
I just tried those between my lack table and bamboo butcher block. Also under my amp which sits on a lack table. They ain’t coming out.
