Muse Model 18 subwoofer

I should begin this review by confessing that I've never been a fan of subwoofers. Most subwoofer systems I've heard have been plagued by a familiar litany of sonic horrors: poor integration between subwoofer and main speakers, boom, bloat, tubbiness, slowness, excessive LF output, and an overall presentation that constantly reminds the listener he is hearing a big cone moving. To me, subwoofers often sound detached from the music, providing an accompanying thump that bears little relationship to the sound from the main speakers. Rather than revealing the music's harmonic underpinnings, subwoofers often obscure them in a thick morass of featureless boom. In addition, adding a subwoofer often destroys the qualities of the main speakers that made you buy them in the first place—just to name a few of my observations (footnote 1).

Other than that, I like subwoofers.

Given my disposition toward subwoofers, why on earth would I ask a subwoofer manufacturer to send me one for review? Well, there are several reasons. At the Winter CES I took a listen to the Muse Electronics Model 18 mated to a pair of Rush Sound Monument 2s and was encouraged by what I heard—seamless integration, quickness, no bloat, and unbelievable extension. In short, not your typical subwoofer. In addition, the Model 18 incorporates some innovative design techniques which, to my knowledge, have never before been used in a subwoofer. Finally, I have great respect for the design talents and audiophile sensibilities of the Model 18's designers, Kevin Halverson and Jim Rush (electrical and acoustic design, respectively). (Theirs is one of the few rooms at shows that rely primarily, if not exclusively, on LP playback.)

What really piqued my interest, however, was the Model 18's "personality cards," a series of small interchangeable printed circuit boards that adapt the Model 18 for use with a variety of popular loudspeakers. On hearing that a personality card had been designed especially for the Hales System Two Signatures, my reference loudspeaker, I was hooked.

In my review three months ago of the lower-priced of the two Hales models, the $3000 System Two (footnote 2), I attempted to convey this loudspeaker's exceptional musicality while pointing out my reservations about the lack of low-frequency extension. These comments also hold true for the Hales Signatures—both loudspeakers are stunning in their ability to involve the listener in the music, but lack that visceral and vital component of music—the lowermost octaves. The Signatures have a –3dB point of 52Hz, above much musical information.

I saw in the Hales System Two/Muse Model 18 combination ($5500) the potential for world-class performance in a fairly reasonably priced system—provided, of course, that the Muse didn't exhibit any of the unmusical characteristics cited earlier in this review.

Talking about unmusical characteristics, I get a kick out of catalog ads for subwoofers that tout "Thundering bass! Stun small animals and rattle pant legs!" Since when does music sound like thunder? And why would anyone want to stun small animals?

We want to know how they reproduce music.

Technical description
The Muse Model 18 is fairly large as subwoofers go, measuring 25" on all sides. A variety of finishes is available, including clear oak and a stained walnut designed to match the finish on the Hales loudspeakers. The review sample was clear oak, the same as the review pair of the Hales System Two. When placed between the pair of Hales, the Model 18 looked like it came from the same factory, such was the similarity of finish. The sidewalls are made from ¾" veneered particle board, and all edges are radiused hardwood. The top panel is a flat-black material, surrounded by the hardwood. Four feet lift the unit 1¼" from the floor.

The rear panel holds a large (16.75" by 7.75") metal plate on which the electronics are mounted. The plate is dominated by a heatsink that protrudes from the panel, providing dissipation for the unit's internal amplifier. Three knobs, marked "Damping," "Level," and "Delay," occupy the plate's top left corner. Four gold-plated RCA jacks (stereo input and stereo high-pass output) provide line-level system connection. On the opposite side of the plate, a small door held in place by hex bolts allows access to the personality card socket. A captive AC cord, line fuse, and power on/off switch finish off the rear-panel plate.

The Model 18's bottom is made from two particleboard panels separated by a 2"-wide slot that runs down the unit's width. The slot provides the acoustic outlet for the dual 10" woofers. Removing the bottom panel closest to the electronics plate gives a clear view of the Model 18's innards. The amplifier, mounted on the plate, is one half of a Muse Electronics Model 100 stereo amplifier (reviewed by Corey Greenberg in Vol.14 No.4). When loaded by the two woofers, it can provide 225W of power output. A large transformer and two 10,000µF electrolytic filter caps, each nearly the size of a soda can, form the bulk of the power supply. This supply is quite beefy; the stereo Model 100's supply is used here to power the summed mono channel.

Opposite the amplifier, on the internal particle board panel that makes up the slot, lies the crossover board. The 10.5" by 8" board contains the LF summing circuit, high-pass filter, low-pass filter, and crossover power-supply filtering and regulation. The crossover power supply is fed from the amplifier's 10,000µF filter caps; additional filtering and regulation are performed on the crossover board. A ribbon cable runs from the crossover board to the personality card socket mounted behind the rear plate.

The input RCA jacks on the rear plate accept a stereo line-level signal and output a high-pass–filtered, line-level stereo signal that drives the main amplifier(s). This filtering is done on the crossover board, which also sums the stereo input signal to mono, then low-pass–filters it before the Model 18's internal amplifier. The crossover uses discrete transistors in the high-pass section and op-amps in the low-pass. The circuit topology is interesting: all filtering is passive, surrounded by active buffers. Kevin Halverson feels that passive filters provided better sonics.

Three buffers and two filters per channel comprise the high-pass section. The buffers are wide bandwidth, with high input impedance and low output impedance. This ensures that the load impedance seen by the filters is constant at all frequencies. The final buffer drives the "HF Output" RCA jacks.

Each channel's passive filters are connected by the previously mentioned ribbon cable to the personality card socket. This allows the filter frequencies, damping, and slopes to be modified by whatever personality card the user installs in the socket. Changing personality cards is fast and simple, taking about two minutes to swap cards. There are now 28 personality cards available, with more being added as demand suggests. Personality card parameters are chosen after several samples of a particular loudspeaker have been measured. The lowest possible crossover frequency is chosen in an attempt to maintain the characteristics of the main loudspeaker as much as possible. In loudspeakers with severe phase shift at the suggested crossover frequency, a higher frequency is chosen along with a steeper slope to provide a smoother transition to the Model 18.

The low-pass filter incorporates sixth-order equalization, damping control, a delay line, and a level control. The low-frequency cutoff is adjusted by the damping control, varying the –3dB point between 18Hz and 25Hz. To ensure correct phase relationship between the subwoofer and main loudspeakers, a delay control provides up to 6ms of delay in the low-pass section. This amount of delay corresponds to physically moving the subwoofer nearly 7'.

When the Model 18's designers set up the subwoofer in my listening room, they used an interesting technique to adjust the delay control. Kevin Halverson had built a relay box that polarity-inverted the signal passing through it. The relay box was connected between the main amplifier's output (the VTL) and one of the main loudspeakers, and a long cable allowed the relay to be operated from the listening chair. With one person behind the Model 18 to adjust the delay control and one person in the listening chair with the remote polarity inverter, a 52Hz sinewave—the transition frequency between subwoofer and main speaker—was fed through the system. The relay was switched back and forth as the delay control was rotated. With the main speaker's polarity inverted, the optimum delay setting is achieved when the null is greatest—indicating the subwoofer and main speaker are 180° out of phase. When the inverting relay is removed from the system, there should therefore be correct phase alignment in the system. This technique reportedly saves weeks of trial and error in the listening room.

Moving on to the acoustical configuration, two 10" long-throw woofers are mounted vertically in the cabinet, firing into the slot that runs down the enclosure's center. The acoustical output is omnidirectional, appearing around the clearance between the cabinet's bottom edge and the room's floor. At least a ¾" clearance is needed, requiring that the Model 18 be put on feet or Tiptoes in thickly carpeted listening rooms.

The Model 18 uses a sixth-order alignment, with a tuning frequency of 18Hz. This high-order alignment was chosen for its deeper extension compared to fourth-order (half an octave less extension) and second-order alignment (1½ octaves less extension), given the same drivers and enclosure size. Although the sixth-order alignment increases the group delay, it shifts it to a lower frequency, presumably making it less audible. According to Muse, the sixth-order alignment produces less group delay above 30Hz than even a second-order alignment in the same enclosure volume.

Incidentally, the Model 18 is an outgrowth of a subwoofer shown at Stereophile's 1990 Hi-Fi Show in New York. That subwoofer used the same electronics, but had two 18" woofers in each huge cylindrical enclosure, with a weight of 300 pounds apiece!

Overall, the Model 18 appears to be a well-thought-out product. The construction quality is excellent, especially the cabinetry. Although the enclosure is fairly lively when rapped with the knuckles and isn't braced as extensively as the Hales Signatures, it was designed to be relatively resonance-free over the narrow band of frequencies it reproduces. I was concerned, however, about the fact that the high-pass–filtered signal is put through about 6' of ribbon cable, not the ideal conductor for audio signals. Although the cable is about 18" long, the signal goes up and back twice: the personality card is connected to each channel's two passive filters.

I spent nearly two months with the Model 18 in the usual reference system. The three loudspeakers auditioned with the subwoofer included the Hales System Two Signature, Hales System Two, and the Phase Tech PC-80. For comparison, I had on hand a Phase Tech PC-90 passive subwoofer ($550) and an Infinity Modulus active subwoofer ($2000). (The PC-90 is reviewed next month.) Although neither is as expensive or as ambitious as the Model 18, they nevertheless provided a basis for comparison.

The auditioning began with the Hales System Two Signatures in their usual location with the Model 18 between them and 26" from the rear wall (measured from the back panel).

Before hearing the system with the Model 18 installed, I was concerned that its high-pass electronics would degrade the sound. I'm always wary of adding electronics to the signal path, preferring instead to remove passive and active devices—replacing a preamplifier with a passive control unit, for example. This is especially true of the Hales Signatures driven by the VTL 225 monoblocks: the Signatures are very revealing of upstream electronics, and the VTLs have a sweetness and musicality uncorrupted by solid-state electronics. If the Model 18 introduced any grain or hardness to instrumental textures, or interfered with soundstaging, I would have been unable to recommend it—regardless of its low-frequency performance. Natural timbres, soundstaging, and lack of electronic brittleness take a much higher priority in my book than bass extension. Any detrimental effect on the overall presentation and the Model 18 would be an unwelcome and brief visitor to my listening room.

Imagine my surprise, therefore, when the mid and high presentation improved after adding the Model 18. The soundstage became noticeably wider, there was greater clarity and transparency in the mids, and transient attacks were sharper and more lifelike. The Model 18 did add a trace of hardness to the presentation, but the improvement in soundstaging and dynamics was well worth the tradeoff. The most obvious reason for the improvement is that the Hales didn't have to try to reproduce very low frequencies with their two 7" woofer/midranges operating up to 2kHz. The Model 18 kept low frequencies out of them, thus letting the woofers do their job in the midrange without being burdened by large cone excursions

(When the Model 18 was first connected to the system, the improved soundstage focus and width were immediately apparent to everyone in the listening room. Kevin Halverson offered his theory of why image outlines sharpened and soundstage width increased: He thinks the improvements are due to an increase in overall system bandwidth. Instead of the SP-11 driving the VTL 225W monoblocks, it saw the Model 18's input buffer. He theorizes that the VTLs, with gain at the first input stage, load the preamp with high capacitance. This capacitance he refers to is not intentional capacitance, but parasitic capacitance caused by the Miller Effect. Vacuum tubes have capacitance between the grid and the plate, which is multiplied by the tube's gain. This is the so-called Miller capacitance that puts capacitance in parallel with the input resistance, contributing to HF rolloff just above the audio band. By buffering the signal in the Model 18's crossover, the VTLs are driven by a much lower source impedance device (and through a shorter interconnect) than the SP-11, increasing the system's bandwidth. Although the Model 18's input impedance is 25k ohms, less than the VTL's 137k ohms, the 25k ohms is reportedly nearly purely resistive.)

The Model 18 passed the first and most important test.

The next most important factor in my musical hierarchy is the ability of the subwoofer to integrate with the main loudspeakers. The two should sound as one, with the listener never reminded of the subwoofer's presence. Again, the Model 18 took me by surprise. The transition between the Signatures and the Model 18 can only be described as seamless. This is a word used too liberally in describing subwoofer performance, but in this case it is deserving. There was a coherence to the entire bass presentation that enhanced rather than detracted from the music. Solo piano and acoustic bass are particularly revealing of discontinuities. On Dick Hyman Plays Fats Waller (Reference Recordings RR-33CD), descending and ascending left-hand lines (as in "Viper's Drag") were continuous and undisturbed by the Model 18. Other piano recordings—including Stereophile's latest LP, Intermezzo—were similarly impressive in this regard. There was never the impression that the instrument's character changed as it crossed the transition between subwoofer and main speakers. (The lowest note on a 9' piano is 27.5Hz.)

Plucked acoustic bass, featured in much of my favorite music, was a joy. There was a weight and depth to the instrument not conveyed by the Hales themselves. In addition, the textures were round and liquid, with precise pitch definition. Ray Brown's excellent bass work on Bill Evans's Quintessence LP (Fantasy F-9529) was particularly impressive. It had a body and finely detailed texture that gave it an air of presence and palpability. Its character was the antithesis of synthetic, wooden, and uninvolving.

At the same time, the presentation never became tubby or bloated—the Signature's agility and precise pitch articulation remained intact. The Model 18 subtly enhanced, rather than overpowered, the Signatures. This was another source of concern over adding the Model 18 to the system: the Signatures' bass is among the best defined and most articulate I've heard. I could easily imagine the Model 18 blurring the Hales' precision. I was again pleasantly surprised by the Model 18. All the qualities that make the Signatures' bass so musical were left intact, while the Model 18 provided effortless extension below the Hales' LF cutoff.

In addition to adding body and depth to instruments with some energy in the Model 18's frequency range, recordings of instruments with substantial LF content were nothing short of stunning. The Dorian Pictures at an Exhibition (DOR-90117), obligatory in subwoofer demonstrations, took on a radically different perspective. The instrument's—and thus the music's—size, power, and tonal shadings were fully realized. I quite enjoy this performance apart from its superb sonics; through the Model 18/Signatures combination, it was transcendental. Correct reproduction of the bottom two octaves is essential to experiencing the full impact of this music, the pedal tones, some reaching as low as 16Hz, being the tonal foundation of the work. The Model 18 reproduced them with effortlessness, power, and authority. Even with the lowest notes at high playback levels, the Model 18 never showed signs of strain. In addition, the depth to which the Model 18 reached was stunning. The sheer physical power of this music was enormously satisfying. At the conclusion of "The Great Gate at Kiev," I felt physically and emotionally drained in a pleasant way, unable to continue the auditioning until the following day.

Naturally miked recordings took on a new size and sense of space. The feeling of the listening room being replaced by an expansive acoustic environment was greatly enhanced by the Model 18. Much of a hall's character and size is conveyed by low-frequency reverberation—cues not audible without a full-bandwidth loudspeaker. Although much of this information isn't consciously heard as LF reflections, these cues nevertheless infuse the presentation with a "bigness" and feeling of a vast expanse of space.

The Muse Model 18 also contributed greatly to music in which electric bass and kickdrum work together to drive the rhythm. In the studio, much attention is paid to the interaction of bass guitar and kickdrum, both tonally and rhythmically. With correct tuning, good-sounding instruments, and great players, these two instruments form a synergistic combination that infuses the music with life and vitality. After adding the Model 18, music took on a new sense of vigor and energy. High-energy rock, fusion, and blues became even more high-energy with the Model 18. Importantly, kickdrum didn't become blurred with the bass—it retained its dynamic punch and tonal integrity, working with the bass to propel the rhythm. Coupled with the superb transient abilities of the Signatures, the Model 18 produced an overwhelming feeling of transient impact.

Listen to the superb Sheffield Drum Record (Sheffield Lab CD-14/20). No other drum recording matches this one for capturing the transient steepness of a stick hitting a drum head—making the recording ideal for assessing a system's dynamic performance. What was especially noteworthy about the Model 18 was its ability to reproduce kickdrum without slowness and overhang. The initial impact was sudden, forceful, and razor-sharp, and the decay was equally fast. There was no smearing of the transient—at either edge. This lack of overhang made the presentation taut, quick, and agile. There was a complete lack of plodding slowness, the characteristic that makes the kickdrum lag behind the music, putting a drag on the rhythm. There was a foot-tapping dynamic bounce to the bass that infused music with drive and energy. Despite its delicacy and ability to reveal nuances, the Model 18 can rock'n'roll when appropriate.

I do have a few complaints, but these are more a result of recordings than the Model 18. Some recordings produced very disturbing thumps and inaudible pressure waves from footsteps, bumped microphones, and even a piano's pedals. At times, there was no audible perception of low frequencies, just a queasy feeling and the sound of the listening room's walls creaking under the pressure (the house is virtually new!). On Dick Hyman Plays Fats Waller, for example, the pedals produced distracting thumps that I'd never heard before on this recording. On the first track of Jan Akkerman's CD The Noise of Art (IRS IRSD-82041), the synthesized bass has very low-frequency components completely out of proportion to the rest of the music. I suspect that the engineers, lacking a monitoring system having the Model 18's subsonic extension, were unaware of these low frequencies.

Another minor criticism—again with recordings—was the need to adjust the Model 18's level control for different recordings. Most records and CDs were about right with one setting, but if there was excessive bass on the record, the Model 18 made it overpowering. What would have been a little warm and full on the Hales Signatures by themselves became omnipresent and annoying through the Model 18.

The Muse Model 18 subwoofer is an exceptional product worthy of my highest recommendation. It has forever changed my standards of low-frequency reproduction. Quite apart from its ability to reproduce the lowermost frequencies with an effortless authority, its dynamic agility and superb resolution of textures and pitch, what really makes it special is how easily it disappears into the music, never becoming obtrusive or sounding like a subwoofer. The integration with both pairs of Hales and the Phase Tech PC-80 (this with a personality card for a different speaker, no less) was nothing short of stunning.

I suspect that if the Model 18 can integrate so well with the Hales System Two and System Two Signature, it will work with many other loudspeakers. The two Hales models, with their tight, precise bass, presented the Model 18 with a tough integration challenge. If the Model 18 weren't up to their standards, the transition between them would have been thrown into sharp relief. (I didn't audition the Model 18 with planar loudspeakers, however, which can be more difficult to integrate with a subwoofer.)

Further, the Model 18's electronics are clean, transparent, and didn't add veiling, glare, or hash to the presentation. In fact, many aspects of mid and treble reproduction improved after adding the Model 18, especially soundstaging and resolution of image outlines. The trace of hardness the Model 18 added was more than compensated for, in my opinion, by its improvements in other areas.

A question raised—and answered—during this review was of the importance of bass extension in conveying the musical experience. Quite apart from Telarc cannon shots, sonic booms, jet takeoffs, and other dubious reasons to buy a subwoofer, there is something about bass extension—when done right—that opens up a whole new musical vista. To feel the full measure of the music without the distracting and unmusical side effects is an experience I may never be able to live without.

If you're in the market for a subwoofer, audition the Muse Model 18—but be prepared to be dissatisfied with anything less.

Footnote 1: I refer to the majority of poorly executed subwoofers, not all subwoofers.

Footnote 2: Vol.14 No.4, April 1991, p.200.

Muse Electronics
P.O. Box 2198
Garden Grove, CA 92642-2918
(714) 709-4815