AV123 Rocket UFW-10 Subwoofer Review

Even though I'd heard ahead of time about the piano black lacquer and rosewood finish of the AV123 speakers (the other option is Birdseye Maple) I was not prepared for what awaited my eyes as I opened the UFW-10 subwoofer. At 52 pounds in the carton, the UFW-10 package seems quite heavy for its rather diminutive outside dimensions. To protect its products AV123 uses a double-box technique more commonly found in the pro-audio field for shipping amplified studio monitors.

A point (yes it's a pun) to be made about AV123's foot design is that there is no choice for either rubber feet or hard points. It is hard points only. Also thoughtfully supplied are four nicely machined 23mm diameter x 3mm thick brass discs with center indentations which allow the wide-base brass-point feet to rest on a hardwood or tile floor without puncturing or scratching the floor material. The quality of these solid brass feet and extra wide width of the brass cabinet inserts on the bottom black lacquer end-cap imply attention to detail usually reserved only for speaker systems retailing for many times more than the UFW-10's $599 SRP.

1. Precisely how the pointy foot physically attaches to the subwoofer cabinet and exerts leverage on its mating cabinet insert might be cause for concern.
2. Sir Isaac Newton's first law of physics, "For every action there is an equal and opposite reaction." holds true especially well for subwoofers.

The woofer cone of this sub is a hybrid sandwich of a black-anodized aluminum, single-dish diaphragm bonded at the back to a heavy pulp substrate. This clever and expensive construction gives the non-bending "perfect piston" performance of metal while the pulp substrate damps any high frequency ringing effects of aluminum. At the same time the combination of the two materials adds substantially to the moving mass of the system which usually allows for better low end performance.

The cabinet's front baffle is just under an inch in thickness measuring 22mm (0.86"). The rest of the five surfaces appear to be closer to 18mm (0.70"). There is also an 18mm top-mounted side-to-side brace. Structurally a good idea given the pressure generated in this sealed-enclosure subwoofer.

The amplifier module is a self-contained unit utilizing a solid feeling plastic rear enclosure. This enclosure keeps the air pressure inside the cabinet from transmitting air noise through portions of the amplifier plate such as the female RCA connectors. In many less well-built HTIB subwoofers I've seen the plastic rear enclosure used on sub-amps is sometimes too thin-walled or not heavily braced. This can cause an "oil-canning" wherein the whole plastic surface acts like a diaphragm, pushing whistling air out an RCA hole. This is not the case with the USW-10's plastic enclosure. It appears very well braced and solidly made. Pressing hard, I couldn't get the large plastic back wall of the sub to budge at all.

Finally, the two sidewalls and top and bottom inside the enclosure are lined with 1/4" felt batting. Given the extremely long wavelengths of the frequencies subwoofers are meant to produce it is still curious to me when I see any type of insulation included in a subwoofer. I do know though that it seems equally odd to Chinese assembly-line workers who make many types of (full-range) speakers, all of which could really use the insulation. So the inclusion of the felt material in this subwoofer may just be an attempt to not confuse the workers who make these several types of loudspeaker cabinets. Install insulation in all models and you know you've always made the correct choice.

To get decently accurate measurements subwoofers need to be tested outdoors. I used the back parking lot and the LMS (Loudspeaker Measurement System software program by LinearX) of Speaker City USA in Burbank, California. Tested outside, subwoofers can be measured very accurately using the ground plane measurement technique as seen in the photograph.

To protect the UFW-10's cabinet I placed a heavy blanket down on the asphalt. The AV123 sub was laid on its side on top of the blanket. One meter away the LMS microphone was placed on the other end of the blanket. Setting of the rear amplifier controls were as follows:

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!

Okay, time to set-up for the flattest bass response at the listening position. We're trying for the highest overall SPL using the least amplifier power. Subwoofers need lots of spare power available.

If your HT set-up is in a living room corner like mine and you're starting with a single UFW-10, placing the sub into that corner can give you a potential of as much as an 18dB gain. This is free low frequency boost! (Qualification time: 18dB is the maximum theoretical gain that can be achieved when going from a 4pi anechoic chamber environment, which is like suspending a speaker in a spherical space, to a room corner which is basically a 1/8th pi environment)

Note that since this AV123 sub has the single-band parametric room-mode correction the dire warnings we've all read regarding corner placement of a sub go right out the window. Yes, corner placement does get you a lot of free gain but it will also typically generate a pretty good-sized room-mode bump. With the built-in single-band parametric EQ, however, the room mode will be tamed as the bass energy is more uniformly re-distributed across the low frequency spectrum during the calibration procedure described in AV123's Owner's Manual. You'll now be able to hear, perhaps for the first time, smooth, delineated, bass.

If your system set-up falls into the more common flat front wall placement, a single or even double subs at the one third point of the wall on either side of the center channel should also work well. Wall placement can give a 12dB boost in frequency though, like corner placement, in the real world the gains are usually less than the theoretical 12dB and 18dB maximums.

One critical step is to mount the Radio Shack meter on a tripod and situate it at exactly your ear level in the primary listening position. And pay attention to the dB correction values given for the Radio Shack meter in the instructions. The strength of a room mode at your listening position does not mean you can skip the tripod and just lay the RS meter on your sofa. The measurement won't work as well. So take the time to help the set-up procedure work correctly and you'll be rewarded with tight, tuneful and well differentiated bass! When you hear a really well recorded DVD such as "Heat Wave" from the "Standing in the Shadows of Motown" disc you'll be absolutely amazed that you put up with that one note bass for so long!

I'm going to divide the five star rating system Audioholics has been using for their electronics and loudspeaker reviews so far into half or quarter stars. I do this for several reasons:

My first reference subwoofer is the ( now discontinued) Infinity Intermezzo 1.2 12" acoustic suspension sub with the R.A.B.O.S. single-band parametric EQ and 850 watts dynamic power (originally $1800). The second sub is the currently available Infinity Beta CSW-10 10" acoustic suspension sub with R.A.B.O.S. and 650 watts dynamic power ($1000). The Intermezzo 1.2 is mounted in the corner behind my Sanus equipment rack atop which sits my 40" Mitsubishi TV. As measured and plotted manually, this sub has a virtually flat ±1dB, 20Hz to 80Hz frequency response, at the listening position 10' away. The CSW-10 is mounted behind the listening position and 8' from the listening position.

Since I would be using one or two front mounted UFW-10's for this listening comparison it was decided to leave the CSW-10 unplugged and to compare the single or dual CSW-10's to the single, reference Intermezzo 1.2. Here's what I found out during initial calibration of both the single and dual UFW-10 subs:

My reference sub plays this segment back showing excellent delineation of each low note as the baseman moves skillfully up and down the scale. He could be in the room with his big Marshall amp behind him. The illusion is pretty convincing and the control of a very powerful amplifier over a highly damped 12" subwoofer is evident. Though an electric bass sounds loose by nature, in the hands of a skilled player the initial attack of the ~40Hz to 50Hz notes is what gives this instrument its transient snap. If this note sequence were put on a 'scope the amp's entire 850 watts might be seen to clip. This test is that difficult.

Playing back the same 30 second sequence over the pair of UFW-10 was surprising. Yes, there was a small loss of control as evidenced in the initial string plucks but unless one could A-B one system over the other it would be hard to say. Set-up against the front walls under both the left and right front speakers respectively the AV123 subs blended beautifully with the satellite speakers and were able to attain the same 104dB peaks with their extreme bottom frequencies remaining full and tuneful.

Unplugging and resetting the overall sub system level for one sub showed a bit more looseness on initial string plucks as the single system was now struggling to output the same SPL as two UFW-10s. That and the loss of 1/2 of the piston area shrunk the apparent size of the bass man a bit. Still though, considering that the voice-over in this opening sequence now registered a too-loud 92dB the single UFW-10 put on a heck of a performance.

"Heat Wave" on cut five of "...Shadows..." showcases two great musicians playing fast low-bass lines on drums and electric bass. It is here that the value of parametric EQ shines best. Both single and dual set-ups of the UFW-10s could clearly delineate the tonal differences between the two bass instruments. Both set-ups were also able to powerfully convey the low frequency syncopation happening between two musicians while the rest of the very large ensemble played instruments above the subwoofers' range. In my experience this wonderful low bass musical nuance seldom, if ever, is found in subwoofers in this price class. Correctly set-up, single-band parametric equalization is the reason.

Moving onto movies and sound effects, one of my standard references is the submarine adventure classic U-571. The depth charge scene spotlights the fact that explosions heard close- up do in fact have a very sharp leading-edge wallop which can be very difficult to reproduce.

The total envelope of a well recorded explosion has a leading edge lasting perhaps 10 milliseconds after which the sound continues to build yet becomes a bit more blunted sounding as upper bass harmonics enter. Finally the explosion sound-envelope closes as the harmonics take over adding a "fuller" more rounded sound to the overall effect.

On lesser systems in the UFW-10s price class, and without parametric equalization, it is usually only the sound of these harmonics which are heard and perceived as "the sound of the explosion". Listening to a single UFW-10 the explosive leading-edge transient is still in evidence while the dual UFW-10 set-up portrays the whole explosive picture more clearly and convincingly.

The curve shows the free-air, frequency response measurement (by ground-plane method) of the UFW10 Subwoofer with a 500 millivolt input. The single-band, parametric equalizer function was out of circuit. Average SPL is judged to be 104dB. Given a 104dB SPL average level the following observations/specifications can be assigned to the system's low-end response characteristic:

The higher mid-bass frequency roll-off characteristic of subwoofers is quite important too. The UFW-10 sub has good, flat extension above 100Hz where it starts to roll off very gradually. A gradual roll-off such as this helps with the integration or "splice" as it's called between the subwoofer and the satellite speakers. A gradual roll-off as seen here usually indicates that a slight mid-bass EQ curve may have been applied electronically to alter the measured acoustic response as seen here.

A gradual roll-off like this is complementary when other software roll-offs will be applied to the system such as Dolby Digital or DTS. Specifications for the low pass characteristic:

This frequency response curve is fairly linear. A very tight (and honest) specification for frequency linearity would be 30Hz to 108Hz ±1.75dB.