@pindac The artificially applied kinetic energy is just a very rough indicator. @dogberry relates that thumps make it through with his Soundsmith which means that low frequencies are being transferred to the stylus of every cartridge, but one can ponder why he hears it most with the Soundsmith. What you are referring to as "natural kinetic energy" I call environmental rumble. You have subwoofers. If you can see the drivers, place your stylus down on a stationary record and turn off any low frequency limiting filters. Turn the volume all the way up watching the subwoofer cones. Now you can see environmental rumble which occurs at very low frequencies. Many suspensions, even the lowly LP12 are capable of isolation the cartridge from environmental rumble. Hanging suspensions such as the Sota, Basis, SME and Oracle are the best at it as are the MinusK and Vibraplane platforms. I can not speak for any others. To work a suspension has to have a resonance point below the frequency of the rumble, below 3 Hz is optimal. Done correctly an isolating suspension will also protect from foot falls. Done poorly a suspension can make footfall problems worse, the LP12 being a great example.
Vibration Question
Warning to the sensitive: involves tonearm pods.
I know this topic is beyond the pale to some, but my tables cannot take a second tonearm (once upon a time, though, they did), and I enjoy variety in cartridges. I have bought four pods so far from Lee Drage at Acoustand, two plain and two with built in micrometer VTA adjustment. But I discover the airspace around the tables is too congested with six arms, as well as introducing some grounding issues. So, as I told pindac the other day, I started to experiment with using two pods per tonearm. Not just a simple 'if one is good then two must be better' but for practical reasons. Firstly, a pod resting on three spikes weighs about 10lb, but it doesn't take much pressure on the distal end of the arm panel to cause it to tip. One can spoil a carefully set up alignment that way, and if it continues tipping a disaster could happen. So, I thought, why not place a pod under the distal end of the tonearm panel, and prevent that happening?
But then a second thought came along: if the second pod were firmly coupled to the panel, I would double mass and damp vibrations even more. That's a bit theoretical to me, as my oak chest weighs ~350lb and I can stamp on the floor next to it and not disturb a playing stylus. But rigidity is rigidity. So I asked Lee if he could make me a double ended panel with an SME mount centred in the middle. Roughly, like this:
He agreed, and pointed out I would have to forego the VTA adjustment, unless one were to place a screw at each end! I can use the SME mount itself to adjust VTA. though, so that's OK.
Here, finally is the question: he thinks I am simply introducing twice as many vibrations (external, I think he means) into the tonearm by having it rest in two sites on the oak chest, and that I would be better off having one end of the tonearm panel free-floating. My view is that rigidity is paramount, and if a built-in tonearm on a table is firmly coupled to the table then I am moving a bit closer to that ideal by having a firmly coupled chest-table-pod system. What say you?
Showing 7 responses by mijostyn
@dogberry Put the stylus down on a stationary record and turn up the volume. Take a teaspoon and tap the oak around the turntable. You should not hear anything. |
Well, go figure. I think you are looking at it from the wrong direction. Three points describes a plane. Four feet rock. When it comes to mechanical devices simplicity is almost always best. The fewer pieces you have the fewer resonances and interactions you have to control. Ideally you would have one critically damped non resonant chassis to which the tonearm and platter bearing are securely bolted. The Basis Inspiration is an example of such a turntable. The problem with this design is that it can get messy if one wants to switch tonearms. Turntables like the Linn LP12 and the Sota Sapphire use removable tonearm boards which can be drilled for each arm. In the case of the Sota Cosmos the board is a 1" thick constrained layer construct of acrylic and aluminum weighing several pounds. It and the tonearm are bolted firmly to a 1" thick aluminum chassis that has been drilled out in a pattern to reduce weight and control any resonance. In this case the spindle is mounted to the chassis and the whole affair is hanging by four dampened springs. Does any of this lead to a better sounding turntable? The honest answer is I have no idea. There are to many variables involved, the quality of the system, the quality of the listener, cartridge set up, tonearm matching and so forth. From a purely technical standpoint it is the right way to do things and I can't not believe that all these "right ways" do not add up. |
That is because you are polite and I am not. I see no reason to support an inferior mounting system whether it works OK or not. The cartridge generates a voltage with relative movement of the stylus to the body of the cartridge. It does not matter which element is moving. It is hard enough to control one element. With an outboard tonearm mount you now have to control three, the turntable, the tonearm piler and whatever it is they are sitting on. With the preferred method only one, the turntable chassis which is very easy to isolate. |
IMHO the only way to mount a tonearm is bolted securely to a stiff chassis that also mounts the platter's bearing. A well designed tonearm board is fine. Suspending the chassis is a must. Examples of such turntables are Avid Acutus, SMEs, The Oracle, Dohmann, Sota and most of the Basis tables. The connection between the platter and tonearm needs to be perfectly rigid and non resonant. (as much as possible) |
I am in agreement with @lewm Just because you cabinet weights 350 lb this does not mean that it does not resonate in any way. Judging from the construction I can see, it does. Ideally you would rigidly mount the turntable and tonearm pod to an isolation platform. |