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I'm building a 3 high/3 wide bay rack out of solid cherry to fit a peculiar space in my living room. I have a lot of woodworking experience and know how to build a tight solid frame, but could use some advice on how to suspend the shelves to hold the gear.
My initial thought was to make individual shelves for each bay and suspend each one on three height adjustable metal points from the front and back stringers of the rack. The shelf itself could be either solid maple or furniture grade plywood. The 3-points gives me leveling and some isolation, but should I be building damping into the rack somewhere, too?. In other words, should the shelf be a wood/rubbery layer/wood sandwich? Or should the elsastomeic material go between the shelf and the stringers?
Or am I overdoing this and should just go for a fixed attachment of the shelves, make everything as rigid as possible?
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My $0.02 is that you should read everything posted by Ken_Lyon regarding rack design principles on AA (former owner of the Neuance shelf) and then implement these principles in your build. Search words: light rigid energy dissipation
a loose loosy fit will dissipate vibration ...a tight ridgid frame will transmit
all depends on what your trying to do ...most gear will respond to both regimes ..but you may only like the sound of one ...
you have to experiment ..there are few short cuts ..
but you can use a stethoscope to listen to how the stand reacts to being tapped ...or the floor next to ..this will give a good indication as to the structures ability to transmit vibration
A friend of mine has a theory I subscribe to. The speakers should be spiked(coupled) to the floor to minimze motion. The rest of the system should be isolated(not coupled) as much as possible to minimize mechanical feed back from the speakers.
A rigid connection to the floor can effectively transfer energy and thus sound to the potential reverberent space beneath a suspended floor and can actually quite easily vibrate a concrete slab.
Whereas the effect of the speaker cone moving the cabinet is absolutely tiny.
However this may NOT optimise your system.
In my opinion however, attaching that much mass (ie the floor) to my speakers was a bad thing and isolating them gave me faster and deeper bass or at least removed mid-bass boom.
As I say, opinions vary.
That's why all the rest of the equipment is isolated from the floor, giving the best of both worlds.
It may be small, but I believe that it was responsible for smearing the soundstage on my speakers. I used some #5 Vibrapods to decouple them from my wood-framed floor. It worked, and the bass boom was reduced, but the soundstage became less distinct and smaller. With Herbie's Big Black Dots, the bass boom was gone, but the soundstage returned. I believe that this is because they de-coupled the speakers from the floor, but are less springy than the Vibrapods, and allowed less reactive movement.
This is consistent with another influence that can compromise the soundstage--RFI. The influence of radio frequency on soundwaves must be of a very small order, but its removal can result in very large changes to the soundstage's size and definition. I heard this with an EP2050 AC filter put into my breaker box, and its sole purpose is to remove electical hash from the power line. It removes impulses up to 1 ghz, so the hash that is removed includes radio frequencies up to that frequency. More controversially, crystals have the same effect on the soundstage--I've heard it--and their piezo-electric properties suggest that they obtain this effect by absorbing RFI.
Putting these two observations together--that small mechanical movements in speakers and small modifications of electronic wave-forms can have large effects on the soundstage--suggests that the auditory cues responsible for this information are very subtle. This also lends credence to the idea that premium parts, solder and wire can make a substantial and real contribution to spatial information. It also indicates why mid-fi components, where the purity of the signal path is marginal, render three dimensional information poorly.
1) Experiment with solid wood (maple, myrtle, ebony?) and as an alternative both birch ply and sandwich. See what sounds best under your equipment to your ears. That's what you should finalize as your shelf.
2) Do the 3 point adjustable/leveling points from your struts as you state (I do that with mine and it's practically and theoretically quite sound). You might consider making these supports out of birch ply or alternatively out of carbon fiber somehow.
3) Use an elastomer of your choice (Norsorex or Herbie's for example) as balls to support the right weight between those 3 points and the shelf mentioned above. That will give you some vertical isolation that is significant.
4) Use whatever your experimentation suggests between your shelving and your equipment chassis, but in my setup roller balls work best there for horizontal/rotational coupling.
Can you clarify for me what you're describing. Are you suggesting that I experiment with using elastomer balls, roller balls, and some kind of height adjustable screw set up, all at three points between the cabinet struts and the shelf? Or use the screws between the shelf and strut and either the balls or roller balls between the equipment and shelf?
I guess another route would be a split shelf: the bottom suspended by three points from the struts (adjustable screws with a sharp point), then a Ginko style ball suspension of the top half, then the equipment, with some kind of isloation footer there. Too much?
Sorry I don't have current pix. The main difference is that I've replaced the tile shelves with symp clones (constrained layer sandwiches) and all the balls below the shelves with Norsorex (dead, sad, unhappy balls); balls above are half inch stainless steel bearings now.But you can see the idea (and this is a DIY 3 point structure): rack points support elastomer balls, balls support shelves, shelves support DIY roller ball clones, which support bottom of the components.
Edits: 04/28/10
Cool. Now I've got the idea. Constrained layer sandwich -- that's like wood/metal/wood, or wood/rubber/wood?
The pic was quite old. I actually moved those black Norsorex balls to below the shelf (now a sandwich instead of the tile you see) and the balls on the bearing surface above the shelf are now half inch stainless steel.
You have the general idea, but it can be done much better than that. Look up the clone ideas here on Tweaks.
You need layers of different density materials from hard on outer sides moving to increasingly "compliant" in the center. So if you look at a Symposium shelf you'll see from the outside (both sides) in: hard aluminum, MDF or birch ply, gatorboard or foamcore layers. That's the idea. I made mine cheaply enough with outer top surface of birch ply, then MDF, then 3 layers of ordinary foamcore (art store stock), then MDF then hardboard (Masonite) on the bottom. Mine are varied because of cost of aluminum and desire to show wood like surface, which I finish as stained wood.
The key to constrained layer sandwiches is that they need to be free to squish together (crude explanation), to move into one another, so your sides, if you have sides, cannot be glued to any but the top or the bottom layer. That allows the proper movement. They act as a seismic sink or isolator, where at each different layer interface they convert vibrational energy to heat energy.
But if you don't want to mock up one of these, and they're cheap to do to test the theory, then just buy some 1/2" thick or thicker birch plywood. It's not as good, but it is better than most solid woods. Solid woods are more tone woods, that is, you're deliberately using their resonant character and native resonant frequencies to "round out" your sonic picture. It's a different idea/mechanism, but it too can work.
I would try out some different solutions and see how they sound. I haven't changed the suspension on my audio rack, but I have experimented with different footers under my equipment and had to listen for what worked in my system. I actually followed some advice about what "the best" footers should be and used Black Diamond Racing Cones under my amplifier. It became quite aggressive and forward so I switched to vibrapods which worked very well (even though they get dissed by a lot of people). The vibrapods worked better for me, but that's probably because my system, untweaked, tends to be analytical, fast and forward. I also tried maple butcher block under my speakers and again got more speed than I needed. In that case, I ended up using Herbie's Big Black Dots, which are somewhat compliant, but not sloppy like the vibrapods I had used before.
I would try a variety of suspension methods and see what sort of results you get. I would also suggest living with the sound for a few weeks before making up your mind, unless of course the sound is obviously wrong.
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