Isolation vs. Absorbtion

Not at all Sean, instead I am a bit embarrassed at your flattery. The general conclusions I have come to are not detailed enough to answer all of the questions you list - but nevertheless so far I believe: it is OK to use multiple structures sitting on top of each other if they are either firmly bolted together or have a point contact - ie spikes or cones; each structure should be light, rigid and damped; there should be no more than one item in the structure that is compliant (ie. non-rigid), that the best place for this compliance is between shelf and component, and that so far the best I have tried are the elastomer E-A-R feet, which have the most even-handed sound without smeering detail. The biggest problem is to achieve the requirement of light, rigid and damped. I believe that if you achieve this in just one place then the best place is in the shelf. All supporting structures under such a shelf can be just light and rigid. Light is important because it means little energy is stored and passed on through the chain - for this reason I think many heavy and damped shelves sound neutral, but smear detail (due to the slow release of too much energy). Rigid is important so that any energy is released as quickly as possible, and because otherwise you may end up with more than one compliant support, causing resonant nodes. Damped is important because if everything was just light and rigid it would ring (the peakiness I have referred to). But I reckon the idea of light and rigid, to make sure energy stored is minimised and released quickly, is in natural conflict with the concept of damping. By its nature damping tries to absorb energy and not return it later, but that is a difficult ideal to achieve in practise. It is in this trade-off that I feel there is as much art as science - finding the trade-off that does the least damage to the music. The reason why I like the items closest to the component to be damped or even compliant (in the case of the feet) is because the component needs to be both isolated from vibrations by the total structure, but also damped. I suspect I am just finding more ways to say what I have said before, but hope this clarifies. But this time I am explaining things in a way that (I hope) is related to Equa's question (isolation or absorbtion). My preference is for the focus to go heavily on isolation, but with a small amount of absorbtion close to the component. I don't like many of the absorbtion products (eg. sorbothane and bladders) because they release energy back into the structure slowly, thereby causing smearing and lack of focus and pace. Used on their own they may subjectively provide an improvement where isolation has not been dealt with well, but I don't think they are the best way to go.

Red, just to clarify something that i've been wondering, have you ever played with "mass loading" any of the equipment ALONG with the various types of isolation / damping type devices ? By this, i mean applying weight to the top of the component ( i.e. sandbags, VPI bricks, etc...) in conjunction with the other tweaks ? My experience is that "lifting" the component higher up of the shelf via cones and "levitating it in air" in effect makes the entire unit prone to ringing and airborne vibrations. This problem does need to be addressed, as it becomes more apparent as volume level is increased. The key to making this work is to find the right amount of weight to damp the cabinet vibrations without adding TOO much mass. Going too heavy will increase the energy transfer from the rack into the component, minimizing the isolation effect of the cones. In order to do this, one must have the weight properly spread out and not concentrated in any one specific area. Freezer sized "zip-loc" type storage type bags filled loosely with a layer of sand can work wonders. Of course, you must pay special attention to ventilation and sources of heat, as blocking off air flow can result in not only a mess with the melting plastic, but also "meltdown" of the equipment in question. Just wondering what your thoughts and experience are on something like this. Sean >

Sean, just a thanks for your follow-up. Jayson

Hi Equa: I also play the isolation game and divide it into two categories as follows. The first step is to isolate the platform or shelf (from external vibration) that is beneath the component. I use Vibrapods for this, Redkiwi is currently using E.A.R. feet and there are many other choices though I do not prefer cones for this purpose. The second step is to "draw" vibration away from the component itself. I use Maple shade cones for this right now and in the past experimented with a set of Racing cones. The first step makes a significant improvement, IMO and the second step takes it up another couple of notches (at least) and allows further fine tuning of the sound. My current set up (from top to bottom) is Persimmon (the cabinet itself)/Vibrapods/Maple shelf (not butcherblock)/Mapleshade Surefeet cones (their cheapest)/CAL player. My DAC is Persimmon/Mapleshade cones/Bel Canto DAC (no soft footers on this set up as of yet, but I will try them soon). I also just tried Persimmon/four pieces of mousepad/MDF/stock soft feet on my Audion amp and this sounded much better than the amp resting on the Persimmon alone and I will experiment with footers other than "mouse pad" and would like to try the E.A.R. feet that Redkiwi mentions. I started out by just isolating am MDF platform for the player with Vibrapods (the player rested on the MDF on its stock feet) and went from there to using various other materials, so the initial investment can be as little as $25.00 to get started. I recommend using both systems from step one and step two for the best results on digital front ends. I sometimes find the use of cones to be impractical (on speakers and delicate items such as tube amps) because I live in the sunny land of earthquakes and do not want to come home to find that my speakers or amp have crashed to the floor which rests way below. The cones did sound wonderful placed between the stands and my mini monitors (the same went for when I tried them on the amp) but I am not willing to take that risk as I do not have a closet full of spares at this time. The same goes for children, pets and the uninitiated around cone mounted gear, earthquakes aside. PS: Just read the first few sentences of this post as they contain most of the useable information:-)

Hi Sean. My view is that mass loading of components has pluses and minuses. I hold to my view that mass in general is a bad thing (for reasons both you and I have referred to above), but is a necessary evil in the pursuit of rigidity and damping. So therefore you are best to only add mass when it has a significant pay-off in terms of damping or rigidity. Mass-loading a component does nothing for rigidity, so the benefits can only come in terms of damping. Arguably, adding a ziplock bag of sand on top of a component is doing three things; it is damping the ringing of the top plate (and to a degree the whole structure) with a substance that is unlikely to feed energy back into the top plate (this should be good); the extra weight will also lower the frequency that the top plate will vibrate at and will cause it to release its energy a little more slowly (this is not so good but is part of the inevitable consequences of damping); the added weight, as you ptu it, "will increase the energy transfer from the rack into the component". Personally I don't think adding weight in this way is the best way to go. It can appear to have beneficial consequences in terms of smoothing out peakiness and can appear to add bass weight (when all it is really doing is smearing the bass). But I shouldn't be so dismissive - it is just that with my overall strategy to the vibration issue, mass loading does not have benefits. If I followed a different overall strategy, such as the "massive" structure approach some take, or the clamp-rack approach that others take then mass loading may make more sense. Using my approach of light, rigid and damped, I believe I can get the good parts of mass loading without the bad parts by using another strategy. Essentially I modify the component by damping it - usually internally. While this is too intrusive an approach for many people, I just see it as good sense when most components are just not put together well. If you have a chance, have a look at a Sonic Frontiers component one day - while I don't particularly like their electronics, the boxes they put them in are brilliant. Much thicker steel panels than you usually find, able to be very securely fastened, judicious use of panel damping and good use of damping/isolation of the electronics from the box. It is poor attention to these details that I reckon using sandbags can ameliorate, but at too high a cost.