Shelf Material

Hi Redkiwi; Are you calling me Garfield? Recently, to audition a tube amp, I pulled my McCormack DNA-2DX amp out of its usual position on the bottom shelf of my large, heavy, all welded steel stereo stand. It has Melamine MDF shelves. After finishing with the tube amp, I put the DNA-2 back in, and over the next couple of days was generally disappointed with music quality which was vaguely irritating-- bass was sort of muddy, mids congested, and upper mids and low treble were slightly bright and even wirey-- but hey, I had been listening to a tube amp for several days (I was also breaking in a fairly new AC cord). It finally dawned on me that one thing I had neglected to do was re-set the DNA-2s vibration grounding spike. The DNA-2 amps have six sorbothane decoupling feet and a coupling grounding spike at the bottom, center, rear of the amp. This spike is threaded directly into the bottom plate of the amp. It's purpose is to couple the amp to the material it sits on. Yes, I know this sounds contradictory,ie to have both decoupling and coupling mechanisms built into the same component, but it REALLY works. After I screwed the "spike" down to the point where the two rear amp feet were just off the shelf (this is what McCormack recommends) I played some music and VIOLA' the music came back-- bass became deep, tight and solid, mids became more clear and well defined, and best of all the brightness/wireness of upper mids and treble went away. BTW, years ago when Stereophile reviewed the DNA-1 amp, the reviewer commented that the soft feet AND the "spike" were a contradiction and the reviewer didn't think they should "work together", but according to Steve McCormack-- not so, ie they DO complement each other; and hey, S. McCormack invented the famous Tip Toes. I have two points here: (1) this dual approach system really does work on the DNA amps, and (2) So why wouldn't it also work with other components-- at least those that don't have to be perfectly level such as DACs and pre-amps. It would be easy enough to check out, all that would be needed is two Sorbothane feet such as Audioquests Big Feet (or Little Feet), and a sharp metal cone foot (for a tripod arrangement). I don't have either yet, but think I'll round some up to try. Steve McCormack certainly has to be one of the masters of vibration control in stereo components. He is at www.smcaudio.com should you want to contact him. And he is a very nice guy. The above ramble is not about shelf materials, but I think it is certainly germane to your subject. Cheers. Craig.

Caterham: Both shelves (whole and with a hole) were cut from the same piece of MDF, there were no other shelf materials involved. I did not power down the system or move my source, so the comparison was quick and easy. Their was no noticeable difference between the two, though both sounded bad. The shelves were used on my amp only and not the source. The next time I will try 1" MDF with and without the hole. The 3/4" MDF is definitely too thin for the 24" stretch. I have Musical Fidelity X gear (the funny shaped stuff) which limits what I can do. I am really dependent on the platform as I cannot change the feet on the components. I also do not have enough clearance left in the cabinet to add more than 1/2" to the sandwich. I had to power down this morning to add my new dual mono power amp (which has a bad hum in both of the channels past 9 O'clock on the gain) so I will wait a few weeks to try the 1" shelf. I already requested a call tag for the amp and hopefully it can be repaired as it is the only one available. I already tried switching polarity, isolating cords and the power supply, etc., so it is something internal most likely in the separate power supply as both channels are humming. Anyway, the reduced mass theory is sound - the materials in their application were just not up to par for a decent evaluation. Aside from function I have been thinking of how rewarding it would be to design the form of equipment racks as I have yet to see a stock one that I would want in my living room. We have very diversified tastes that range from a late 1800s black lacquered bent wood settee to the original umbrella chair, but none of the racks cut it as far as I am concerned.

I'm going to try one of Caterham's Neuance shelves under my CDP as soon as it gets here, and hope it clarifies the top octave without changing spectral balance. Mark (Redkiwi)...I'm not sure how a suspension would be very different from an air bladder re horizontal microdisplacement. You like it though, eh? Does it jiggle clockwise or downunderwise? Cheers! Ernie

Sorry Craig (Garfish) - slip of the tongue. I have indeed come across and experimented with the single spike idea as Theta have used it in their transports, and I have owned a few of those. I have found that the best footer for an application is very dependent on the shelf used. With something like MDF you can be best to use damped cones like BDR, but spike and soft footers together is also good as you say. But I still don't rate MDF highly. Since my last post I have persevered with the suspending of Corian shelves from a steel rack using thick nylon wire, and tried various footers. (The biggest pain is designing a means of levelling the shelves without introducing vibrations.) The best (after trying several different types) is to use a very hard rubber footer, and Vibrapods work quite well too. Cones are too hard with the Corian, and spikes are definitely out of the question. The use of either (including up-pointed spikes under the shelf) result in a severe resonance adding grain and edge to the midband. The results I am getting are now very very good indeed and much better than MDF or the particle board I had been using which was only a bit better than MDF. While I am very happy with the results, I will not be able to rest until I have tried some of the other ideas posted here, especially the Neuance shelf and the maple butchers block. Ernie (Subaruguru), I am sure there must be microdisplacement, but in any vibrating system there will be microdisplacement. In a suspended system the displacement is larger, but slower moving - whether this is better or worse is for the ears to decide. I hear suspension as sounding very different from the bladder products. To put it in a nut-shell. A shelf sitting on a rack tends to add resonant peaks to the music, damage harmonic structure and reduce depth. Using different compounds just moves the resonance around and some are better than others, but none that I have heard reduce the resonances down even close to inaudibility. Placing a bladder product between shelf and component tends to fix each of these problems pretty well, but adds a new one in that it tends to cause a suck-out somewhere, usually in the mid-bass or upper-bass, destroying rhythm. Suspending a shelf can have various results depending on the wire used, but with thick nylon wire resonances are much reduced compared with sitting the shelf on the rack, with none of the suck-out problems of bladder products. Resonance is not totally eliminated and you can still hear the differences between shelves and footers. In addition to this I have discovered that Corian shelves, used with soft footers, can give terrific results, particularly if you want more power (and I mean a lot more) and articulation in the bass.

To all the speculation about suspending shelves and the effect on sound, Arcici Suspense Rack uses air bladders in combination with suspended shelves, $2000+ many good reviews but price is high. I would recommend reading some reviews to understand how this appraoch works. For more info on what a shelf does, and the theory behind proper construction go to Symposium site http://www.symposiumusa.com/index.html My approach which preserves visual integrety and financial sanity is to purchase a reasonable priced rack system like Target, Polycrystal and use stock shelves and fine tune with cheap isolation tweaks, cones...vibrapods....bladders etc. Isolation tweaks have more effect than shelf thickness and what type of wood/plastic you use.