I have been thinking about supports a lot, and independently of the previous stands thread, which I have just read, have decided the following.
A stand has two jobs--a)to isolate a component from structural vibration, and b) to deal with any vibrations generated or transduced by the component itself.
As for a), structrue-borne vibrations, I understand that most of this resolves to horizontal movement. The sources are the vibrations of the loudspeaker cabinets through the floor, and airborne vibrations flexing the structure and the stand, and vibrations in the ground. Dealing with this calls for compliance in the horizontal plane.
For b), that can be vibrating motors or transformers or bearings, as well as the airborne vibration picked up by the component. Dealing with that requires either damping (which doesn't seem to be the best solution) or mechanical grounding. Most stands chose the latter, trying to provide a good path for enery to reach the floor via vertical rigidity.
Most isolation solutions address only one type of vibration. Sorbothane pucks and the like can isolate from structure-borne vibrations, but leave no way for the vibes generated in the component to evacuate. For this reason, I am not sure that rubber feet make sense (theoretically), though they are under almost all components. I have gotten good results with cones under cd players (Rotel) and half-width Naim preamps.
Rigid solutions like cones and rigid racks give a path for vibration to leave a component, but do not prevent vibration from entering, especially in the horizontal plane.
There are a couple of solutions to the problem. One is somthing like Aurios media bearings or Symposium rollerblocks. These systems use a large ball bearing in a cup, free to move horizontally. But the rigid ball also provides a rigid path to mechanical ground for vibrations in the component itself.
Second, I think Mana works by providing some compliance in horizontally--the Mana sway--especially as phases are added. But it is light and rigid in the verical plane. The extra phases also act to absorb vibrations coming from the floor and the component.
A third solution would be to take a rigid rack, like a cheap Target, and put the whole thing under rollerblocks or the like. Or perhaps a heavy stone slab, to provide the mechanical ground, under and air-table or rollerblocks, for the horizontal compliance. So maybe a Target or Sound Org table, on an MDF board (or a constrained layer board, or something), on Rollerblocks would equal the performance of multiphase Mana.
However, I'm not sure where Fraim fits it. It seems to be rigid, and offer multiple layers, but not horizontal compliance.
Now as to rubber feet, as I said I'm not sure why you would want them as compared to something which transmits vibrations directly away, except to say that hard feet can make the sound hard in some intances.
--Eric
Posted on: 19 November 2001 by Arye_Gur
Thomas,
As I was told (and it is interesting to me),
transistors don't suffer of vibration. Capacitors do, but there is the technology today to steady their boards so they'll not be effected too.
Diodes don't suffer of vibration - and overall talking this is not a problem.
I'm not sure about these as facts, but I know the paople who are claiming these claims and they are engineers.
They say that the differences in sound appear because of the stand influence on the room's acoustic.
The example is the difference between a glass shelf that acts like a mirror and returns all the sound waves to tha room, and a wooden shelf that acts acouticly in adifferent way.
There is an expetion for this if the system lies between the speakers.
As they are saying, you have to put your system on a rack (unless you want to put it on the floor) and the rack's manufacture has to take care that the rack will influence the room acoustic as little as possible.
I know all the time that vibrations do effect stereo equipment, but here there is another claim that comes from ppeople who are working with electronics, I wonder if they are right.
Arye
Posted on: 20 November 2001 by Ulrich Hohn
In the old forum I had to this topic thread, which I present here again:
Before long time someone stated that amplifier on different tables sounds differently good. Thus the search for the best tables started. Hereby a large erroneous trend began, one should have looked instead of its for a method, which stops best the vibrations of the housing.
The housings become lively in three types swinging:
1. by airborne sound, 2. by direct transfer by the floor,
3. strengthening the signal produces for oscillations in the amplifier.
The oscillations are strengthened, if the housing is on a wobbly table.
This error is the only one which is in the meantime perfectly avoided by common
hifi-stands.
Active absorption of the housing takes place only sporadically, in which the feet were designed accordingly (Nap500). The effect is however small, because only the dead weight of the amplifier is used for the absorption.
With my search for possibilities the oscillations that of housing to reduce, I tried much out. The break-through came only by my sand absorption. Details see http://hu.fzk.de/hu/hifi/naim/index-english.html
If 4 sand bags are appropriate under and 4 over the amplyfier and press on the bags a strength, which is 15 times larger than dead weights, the effect is 2*15 +1 = 31 times so large, as if the amplyfier is placed only on these 4 sand bags. The conversion of oscillation energy to warmth occurs on the surface of the sandgrain. The grain size selected by me is 10 times smaller than with conventionally fine sand. Like that the surface and the effect are also 10 times larger.
Altogether the effect of my setup is (31*10) about 300 times larger, as if the devices are placed on bags with normal fine sand. With the heavy Nap500 is the gain smaller, here achieve I only the factor 90 instead of 300.
Actually I do not like such number play. But how I am intended to clarify the advantages? If I describe the sound with my poor English, a Nap90 owner answers me: My Nap90 with mine setup sounds better than your Nap500 with yours setup!
The gain opposite conventional tables is as large can I not exactly say - however it is enormous.
A usual way to reduce vibrations of Hifi electronics is to install them moddlyless
to the ground. To reach that it can not be avoid, that the devices have to be coupled
closely to the floor. So far I assumed that the sound decrease by vibrations of the floor is negligibly small - as one can errs! The sound decrease is big!
Because I destroy the oscillation energy by sand-subdued boxes I do not require
to couple the devices closely to the floor, in order to place my Hifi electronics
quietly. I placed the sand-subdued boxes on 3-4 pressure springs. These are unloaded
32 mm long, diameter = 20 mm. They create a force of 0.5 kp/mm when squeezing together.
I have payed 1,06 EUR for each spring.
Which gain does this modification bring?
My SBL sounds now as clear in the bass as DBLs, with usually setuped electronics. DBLs act louder and an oktave deeper. But as far as the SBL basses are heard, they are equall to those of the DBL. I prefer a cello solo on my SBLs, the bass is more rapid and the tweeters are decoupled better. With full orchestras the DBLs plays naturally incomparably.
Ulrich
Posted on: 20 November 2001 by Martin Clark
quote:
what structural characteristics make a skyscraper resistant to collapse during strong seismic activity?
Flexibility and damping, ruled by F=ma.
You allow the structure to flex at a controlled rate, so the acceleration of the tower is small enough to keep F within the tolerable limits of the structure. You then arrange for the kinetic energy to be dissipated as heat within dampers fitted at key points of flexion. Obviously there is a limit to what may reasonably be absorbed - so the 'earthquake proof' building is ultimately impossible.
Now if the question is rhetorical... it's a good analogy.
Equipment support can be lively and have strong resonant peak which swamps the nuisance vibration (and above resonance the transmission of vibration rolls off very sharply); or by incorporating more damping, trade off ultimate isolation against better absorbtion at low frequencies and a smaller peak; or make the peak happen so low in the frequency range that its magnitude and damping characteristics don't really matter - sandboxes and the Townshend oil rig come to mind.
The thing is though, treating the room-stand-kit support as a three-body problem is a bit simplistic. The way in which the kit meets the stand is the same problem in minature - and equally important, since in principle you have a whole bunch of series coupled oscillators.
<hpyothetical>
I make a range of hifi components and wish to build a complimentary stand because the market obviously exists. My range of equipment is based on system-wide attention to detail, so it is logical to take a 'systems' view rather than just consider the contribution of the one element. How do I reference the bit that matters to the room? Assembly/production as far as the equipment feet is a given, so I concentrate on the compliance/damping/adjustment required in the rest of the path to achieve a kinematic goal.
The key questions then are limited to deciding what is the optimal behaviour for the board-level assemblies I identify as sensitive.
</hypothetical>
It's no different from Naim's approach to building amplifiers starting with the system ground...
Cheers,
MC
who remembers when threading made discussions like this so much easier.
[This message was edited by Martin Clark on TUESDAY 20 November 2001 at 15:07.]
Posted on: 20 November 2001 by Craig B
My most loved of physics professors was oft to comment, 'rhetorical queries draw the attention of great thinkers'.
His unofficial nickname was 'Dr. Know' and he was keen to use "l-a-s-e-r" interferometry to measure such things as vibrating cone speakers long before Kef and Celestion were pointing them at tweeters. Interestingly, the good Dr. believed that the dynamic behaviour of the magnet and metal basket were as important as the behaviour of the cone itself. When asked why, he would reply 'what keeps you from falling over?'. He preached a systems approach to everything and was considered a bit off of the wall at the time.
So many small speaker manufacturers have grown up around that small uni town that I for one believe that our 'Dr. Know' was, partially at least, responsible for the success of the Canadian loudspeaker market share (of course massive acreage of soft wood lumber and a corrupt government that is more than willing to rape the environment surely have played their part).
Craig
Threading or no, I will certainly keep watch for your posts.
