February 1, 2010

Tweaks . . . That Work!

What with all the ranting I’ve been doing about tweaks this last little while, it was heartening to read the SoundStage! Network’s coverage of the 2010 Consumer Electronics Show and learn that real engineering still rules the new-product roost. Take Stello’s cool new Ai500 integrated amplifier, which at $3500 might represent the biggest bang for today’s audio buck; or the refined design of Parasound’s JC3 phono preamp, with its short signal paths isolated inside subenclosures that are themselves shielded from the power supply by a metal barrier. But enough of that -- I promised you some tweaks . . . that work!

I haven’t tried every isolation cone/pod/blob out there, but I do have an assortment of Black Diamond Racing cones, JA Mitchell aluminum pucks, Nordost Pulsar Points, and some ebony triangles kicking around the listening room. I even played with a Gutwire Notepad (v.1) before it evaporated on me. None of them holds a candle to the best isolation device I’ve tried, which also happens to be the cheapest: the humble Vibrapod Isolator.

It took me some time to figure out that an annoying resonance emanating from my home-theater rack was being produced by my always-on TiVo. This presented me with a terrific opportunity to objectively experiment with various isolation doodads: they’d either subdue the vibration or they wouldn’t. To make a long experiment short, not one of the so-called isolators did anything more than slightly damp the vibration -- except the Vibrapods. With them in place, the vibration was completely contained within the TiVo. I never heard it again. And Vibrapod Isolators are cheap: from $25 for a set of 4.

The architecture of the average Gothic cathedral might be inspired by Heaven, but its acoustics come straight from Hell. Naming a company Cathedral Sound thus throws down something of a gauntlet, or at least a strong implication that the product can work wonders with problem rooms. Cathedral Sound's Room Dampening Panel (model RDP150C) is claimed to offer the damping performance of a large bass trap, but a size small enough (16"W x 11"H x 2"D) to be easily hung on a wall. The key to their performance is said to be their exploitation of the Venturi effect, a physical phenomenon in which, when the pressure exerted by a fluid decreases its velocity increases, and vice versa. The fluid’s velocity can be increased by passing it through a tapered tube, called a Venturi, that lowers the pressure exerted by the fluid.

How does this apply to acoustics? Air is a fluid. When the Venturi-loaded Cathedral Sound panels are placed near room corners, they take in the air, which in those spots can be excessively bass-loaded due to the meeting of room boundaries, cram it through their Venturis, and thereby decrease air pressure while increasing air velocity. The trading of pressure for speed seems to reduce the sound-pressure level of the air passing through the panels, thereby attenuating excess bass energy. I can only surmise that the size of the panels dictates how much air can be pushed through them at a given moment, which in turn likely accounts for the panel’s ability to remove just enough bass energy from the room.

That’s some fine theory, but the great thing about the Cathedral Sound Room Dampening Panels is that they work. They’re most effective when hung on a wall (6" to 8" down and 3" out from the nearest meeting room boundaries), but also do very well when just sitting on the floor in the room’s corners. The effect of the panels was instant and easily noticeable in my room, with marked decreases in boom and bass bloat. This was accompanied by a clearer, more focused midrange that had been masked by the overloaded room. Overall, the Cathedral Sound products were just the ticket for reforming my spacious listening room. The facts that they’re cheap ($90 each, with discounts available for multiple units), and of almost microscopic size compared to traditional bass traps, make them worth a close look. They actually deliver as promised: a tweak that . . . works!

We’re not done tweaking yet, dear friends. Next time I’ll talk about electrical and magnetic tweaks.

. . . Colin Smith