Lewm:
Thanks for your response and for bringing Fremer's measurements to my attention. It sounds like Mr. Fremer is on the right track.
Whatever its failings, Stereo Review did use a consistent methodology of testing turntables. They had a vibrating table and would test the suspension resonance. Objective, not subjective, for what that's worth.
It seems I was not clear in my writings; I apologize. If your turntable has three feet, put a tripod under each for a total of three tripods. If your turntable has four feet, put a tripod under each for a total of four tripods. I'm too lazy to draw a picture using characters! |
Hifigeezer, With all due respect, Stereo Review was a rag. But Mike Fremer did use accelerometer(s) to evaluate the Finite Elemente and the Monaco Grand Prix stands and reported his results in Stereophile. His tests generated quite a furor among devotees of these two very expensive equipment racks. |
"Since the tripod is the most stable base (ask any photographer or physicist)"
Hmmm...you may be a photographer, but you're definitely not a physicist.
And as for "All the best turntables..........now have 3 legs instead of 4"...., well, that remark shows such a lack of knowledge as to be laughable. And I also note that you've changed your experimental paradigm from "taking three tripods, setting up one under each foot?" to "three to four tripods"-I assume that's because you realized that a 3-point base under a square or rectangular plinth is inherently *unstable*-just press lightly down on any corner that no longer has the benefit of a stable foot
It does make me think, though-imagine you had tripods for footers, and then you put *another* tripod under each leg of those tripods, and then *another* tripod under each leg of those tripods, and then......
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Thanks to all for your interest. I have not tried the experiment, I was hoping someone else would. I see lots of posts of people complaining about footsteps bouncing their turntables or feedback from woofers. Perhaps one of those unfortunate souls will invest the time and effort. WalMart lists tripods starting at $15 and I bet some of you could borrow three if needed.
Tketcham gets an "A" on this quiz, both for careful reading and mechanical understanding. I am proposing the use of one tripod per turntable leg, thus three to four tripods total. A tripod can be more stable than a table with four legs. Unless all four legs are EXACTLY the same length, the table can rotate on the two longest legs until the next-longest is grounded. This leaves the shortest leg in the air, so you end up with a tripod but one which is not optimized. As we said in physics class, this assumes all objects are rigid. Each additional leg IN CONTACT with the ground will add stability, but any mismatch of length will cause mismatched load bearing. Yes I am a physicist and yes I should get a life. I agree the WAF for three tripods in the living room could be an issue! The narrow profile of the tripod should in theory make it a poorer antenna for airborne sound waves than a big boxy table. Look at the guy with the microphone on the football sideline; he is using a parabolic reflector to capture the sound.
Considering the megabucks people spend on turntable stands, spikes and cones I am surprised there is not more experimental data on this topic. Try playing loud music from another source or dancing near your turntable and check its output. Let's replace dogma with data!
Why don't magazines test vibration-sensitivity of stands or turntables? Stereo Review did; it should be easier to plot this than loudspeaker or tonearm frequency response. Maybe they like getting ad dollars from the makers of cones and stands. :-)
Regards, hifigeezer |
Tripod stability as an urban legend?
I've always wondered whenever I read the suggestion that a three leg support is more stable than four. Do these proponents think it is impossible for a tricycle to tip over? True that a tripod with three legs spreading out from a central point of contact may be more stable than three perpendicular legs under the perimeter of the object they support but that is not the usual audio application. Anyway, I think stability also relates to the mass on top, the height, and how the mass is distributed.
Anyway, I'm glad to see that others have reasons to doubt the absolute superiority of three supports VS four. |
Hi, Hi,
Seems that some of the posters missed your idea about using a tripod for each of the turntable base feet/points for a total of nine legs. I think it may have merit - "worth a try" - if you could find very solid and stable tripods with easily adjustable height. A surveying tripod with spiked feet might work well. They're used to support equipment that costs thousands of dollars and take very fine measurements. And you could probably find attachment adapters that would screw right into the turntable base. It might look rather goofy but on the other hand it could be an unusual conversation "piece".
Tom |
If you use a photo tripod as a component base you have effectively changed it to a monopod base resting on a tripod base. Seems to defeat the idea of a tri-point component base and replaces it with an inherently less stable monopod platform. |
The people who used to market Linn specifically recommend flimsy tables what do you expect? something serious? |
Reason for a tripod or 3 feet under a piece of gear: (1) Easiest to level; (2) The weight of the supported object will be evenly distributed among the 3 pods, once the object is level and if the tripod is properly implemented, (3) Fewest paths for vibrational energy to travel from the shelf or stand into the component. These are not trivial advantages, but extreme stability is not among them, as others have noted. |
The reason manufacturers use three legs instead of four on a photographic tripod has nothing to do with the superior stability of three vs. four legs. Rather, three legs satisfy the minimum requirements for stability and this balances out the costs of engineering complexity, manufacturing cost, and weight penalties if you use more legs. |
I build turntables that have four feet. Three would be nice because it would be easier to level, but some designs cannot accommodate that feature. Mine is one, and it is very stable. |
3 legs making contact with the floor is the minimum needed to achieve stability. (Insects have 3 legs on the ground at any given time for that exact reason.) That doesn't make it "more stable" than more legs.
A tripod doesn't have any legs exactly opposite of its legs. Hence, you can easily push over a tripod over by taking one of its legs and pushing to a spot exactly between the other two legs. Now imagine adding 3 legs to the tripod, each one 180 degrees opposite of the existing legs. Now try that same experiment to topple the tripod by pushing with the same vector as last time, and you'll find it more difficult. Note that this new "tripod" has 6 legs rather than 3. But yet it's more stable.
So I think that your fundamental assumption of a tripod being more stable than other configurations is flawed.
Michael |
IMHO the real reason that a tripod (vs a 'quadpod') is better is that it is just easier and faster to obtain set up and a horizontal plane. If you think it is actually 'better', try sitting something on it which is not balanced weight wise and see how unstable a tripod can actually be, or have somebody or a pet, bump into it. Learning leasons don't always come cheap. :-) |
You could have listened to a couple of great albums in the time you spent bouncing that around.
Either you have a lot more time on your hands than I do or I am missing something.
With all due respect. |
