Rocket UFW-10: Using Two Subwoofers

I picked a subwoofer as the topic for my first loudspeaker review because I firmly believe that without a lot of up-front attention given to a system's accurately portrayed bottom end the very foundation of both music and movies is stripped of its requisite emotive impact. Avid Audioholics will have read " Loudspe a kers: When is Enough Good Enough " Part 1 wherein I told of my first tri-amplified reference speaker, the one-off Marantz Imperial 9 which had two 10" woofers, equalized dead flat in-room to 30Hz, in each of two stereo full-range speakers (four 10" woofers total).

From that first experience with great bass, I've always remembered the most obvious of credos; that to get clean accurate low bass you need a lot of well controlled piston area (the woofers' usable working area) driven by a lot of clean amplifier power. Make the box smaller, and the power requirements to put out the same SPLs can start to go up almost exponentially.

This need for vastly increased power is especially true in the lowest 20Hz - 40Hz octave of music. Now add the fact that to produce a 20Hz note the woofer must move 4 times further than to produce a 40Hz note and it should become obvious that setting a low end requirement of 20Hz is imposing a very stringent and perhaps unnecessary requirement on your .1 system.

My target low frequency response, to keep a subwoofer reasonably sized and priced, has always been flat to -1 or -2dB at 30Hz. I look at the situation from a viewpoint of size, for unobtrusiveness, versus real-world performance capability. While it may be true that the lowest note on an organ is 16.4Hz, given the choice I'm betting most significant others wouldn't accept a subwoofer at least twice the size as the UFW-10 just for a few scant moments of musical ecstasy when E. Power Biggs hits that open stop 16Hz organ note. Similarly, for the 5% of sound effects that actually reach lower than 30Hz in more than 1 or 2% of all movies, I don't see the attraction either.

My point of reference is and always has been to be able to accurately reproduce the lowest notes on the piano, the harp, the contrabassoon, and the rare five-string electric bass, all of which are closer to 32Hz. Bottom line, I believe a system flat to 30Hz with a -6dB point of 25-27Hz allows the best trade-off in size vs. performance vs. cost.

Small Box with single-band, parametric EQ + Your HT Space = Articulated Bass

Let's assess what we're asking of AV123's UFW-10; a single 10" transducer in a sealed enclosure with less than one cubic foot internal volume. We know it can hit a very respectable 104dB at 1 meter while maintaining a relatively flat 35Hz to 100Hz frequency response. If we put it up against a wall we have the potential of gaining another 6dB from the wall's reinforcement. This is starting to look pretty good from a pure numbers standpoint but don't hold onto that (theoretical110dB) number just yet.

We haven't yet added your home theater room or listening space into the equation. We realize from our forums that the numbers of home theater or music listening spaces which are actually in an easy-to-optimize rectangular box of a room are truly in the minority. The most common home theater room scenario from our readers seems about equally divided between either a rectangular room with the furniture forced up against a wall or a great room, completely open to the kitchen/dining area. And it seems with these to examples that the ceiling is either very high or, in the case of the rectangular room one wall might be missing completely.

The bottom line with the home theater room scenarios above is that very few conform to a 2000 cubic foot or 3000 cubic foot standard which THX and most others in the professional design community use as a design parameter. Consequently, we Audioholics are almost always trying to get a single, underpowered 8" or 10" subwoofer to perform some kind of SPL miracle in a room that is much too large.

Once past the issue of "Will it play loud enough?" (to give the music its essential foundation) the last and most important piece to the bass puzzle is to know how to listen for and appreciate the elusive quality of bass articulation. Of all the parts of the musical spectrum I believe bass quality is the easiest to recognize once you have it. Until recently though an in-depth analysis of the problem with bass quality in home theaters has almost always been glossed-over in most all subwoofer reviews. Why....?

It's a question of the haves (as in those few subwoofers having some form of parametric equalization) versus the have-nots. In one of the last issues of the now defunct Audio magazine a manual set-up, 1/20th octave, single-band parametric equalizer was first introduced by Infinity in their flagship Prelude system subwoofer module. At the time of that article the $6K to $9K Intermezzo and Prelude systems where the only subs with single band parametric EQs.

Most manufacturers still aren't hip to the overwhelming benefits that come along with this capability. And it's understandable why. Infinity's sales department didn't see huge leaps in subwoofer sales with their single-band EQ system because:

So here we are today, faced with a stunningly beautiful subwoofer, that, because of its single-band parametric EQ can be placed anywhere in the room you or the significant other decide, (except, of course, a null). It's priced well and it's flat response bass capabilities just await music and bass lovin' Audioholics who are willing to put in a couple hours up front to get clean, flat, low end like they've never experienced.

Also noteworthy from AV123 is that they listen and pay close attention to us at Audioholics. When AV123 heard that I wanted to use two of their subs for my first full length speaker review they immediately put a two-fer deal up on their site. Buy one UFW-10 at the normal retail of $599 or two for the bundled price of $999!