Fine Tunes #15
While I've gotten less tweaky in my reviews, I still hew to the tenets of resonance tuning. Given that tubes, capacitors, and even integrated circuits are microphonic, placement and support of audio gear is of paramount concern. I covered the basics of this two "Fine Tunes" ago, in July, but this month's column is for tweakers who'd like to understand more about the how and why of it.
It's a big world, Toto, and many listeners and manufacturers feel that resonance control of any kind, anywhere, is nothing but unmitigated malarkey. I believe otherwise. My best advice to both camps? Use your ears and hear what you will. What follows is the received wisdom on these matters, most of which I agree with.
First, consider the component you're dealing with. Is it a tubed phono stage with an ultra-sensitive, low-level signal, or a line-level preamp/player/processor? If the former, you'll want to decouple the chassis from the environment---vibrations coming from buzzing transformers, spinning discs, turntable motors, footfalls, building shake, subways, passing trucks, and airborne acoustic mayhem produced by the soundfield in your listening area as it loads up at high volume. (Think of sound waves as water splashing around in your listening room.)
Sorbothane-type pucks are a pretty cheap means of decoupling the chassis - Vibrapods run only $6 each. K-A-B Electro-Acoustics offers relatively inexpensive Sorbothane II Sonic Domes in three weight classes, or grab the Edmund Scientific catalog and order up a bunch of half-hemisphere Sorbo footers for even less. David Dlugos e-mailed a great suggestion for a cheap and effective footering system: Set your gear up on sawn-in-half tennis balls!
But even in Tweak City, controversy reigns. Informed Sources characterize Sorbothane-type footers---ie, those that transform absorbed energy into heat---as holding and releasing captured energy, creating a ghost or time-smear effect on the sound. I tend to mount tube gear on various types of hard-material footers that couple the component to an energy-absorptive shelf of some kind. I use Bright Star air- and sand-filled products, Signal Guard II closed-cell foam stands, Black Diamond Racing shelves and footers, and a lot of PolyCrystal shelving and footers. (With PolyCrystal racks you can have your cake and eat it too; they're "delivery systems" for substantial resonance-absorbing shelving.) In any case, you can always try bubble wrap and/or a butcher-block equipment support as mentioned in July's "Fine Tunes." If you try bubble, remember its effectiveness depends on the mass of the component you're trying to isolate. If it's very light, the resonant frequency of the component/bubble wrap might be too high. But that can be fine-tuned by placing additional mass on top of the component.
If your equipment is solid-state, don't imagine that footering and shelving won't help. Is the component's chassis light and resonant when tapped, or does it have a heavy chassis and internal damping of some kind? If it's dense, like an amplifier, harder-material footers set into a solid platform would be best. A friend of mine dropped a small wooden cigar box filled with lead shot atop a fairly lightweight Arcam CD player, and coupled that to the MDF (medium-density fiberboard) shelf in his Target stand with original Mod Squad Tiptoes. Even he, a neophyte audiophile with Rotel two-channel/surround electronics, easily heard the improvement. But don't use so much weight that it deforms the case, which might interfere with the operation of the loading tray. As in all things, moderation is advised (footnote 1).
Along with PolyCrystal products and DH Labs ceramic cones, Tiptoes are an inexpensive way to go about mounting equipment, if you'll forgive the imagery. What material footer you try depends as well on the sound produced by a sharp rap o' the knuckles on the shelf. Do that a few times and try to make out if the resulting sound is ringy or resonant, or---better, of course---dull and inert. If it sounds solid, you might try a harder footer; if it's loose and rattly, a softer, Sorbothane-like footer might work best.
Other generalized mounting principles include placing one of three footers under the rotating mechanism of a CD or DVD player. For whatever reason, three footers usually sound better than four. (Well, three points do define a plane.) The chassis of some components are so live and resonant that moving the footers around can change the sound, as can the characteristic acoustic of the footer's material. (Hard materials give a faster sound, soft materials a warmer, slower one.)
One intriguing equipment-support product Sam Tellig wrote about last April seems to attempt to bridge the gap between devices that absorb energy and those that couple it to the supporting structure. Symposium Rollerblocks support components on ball bearings set in polished, oval depressions in the top of an aluminum block. Symposium claims that Rollerblocks drain internally generated vibes and decouple the supported unit at the same time. Hmmm---this reminds me that the Forsell Statement amp has a small bag of ball bearings that sits atop the center front polished granite footer. The idea behind Forsell's balls---and, I assume, the Rollerblocks---is that allowing the chassis to resonate and move about slightly prevents the entire structure from oscillating, which it might do if overdamped and so adversely affect the sound.
You know what's coming: Try marbles, boys and girls (or "aggies," as my dad called 'em). Easy and cheap enough to see if there's any effect on the sound. In fact, if there is a difference, you might concentrate on finding a solution that makes the sound better, in your judgment, not just "different." But any difference will tell you that it works. Just be careful your precious audio component doesn't aggie off its shelf and onto the floor. Crash.
More resonant musings next month. Until then, think up some good "you've lost your marbles" jokes!
Footnote 1: Yes, I do appreciate the irony of such sage advice coming from, of all people, moi---Mr. Moderation.