But that still left a clear gap in the Wilson range. The company hopes that the MAXX, introduced at HI-FI '98 in Los Angeles and priced at just over half the cost of an X-1/Grand SLAMM, or twice the price of the WATT/Puppy, will fill that gap.

Great things should be expected of this speaker. The MAXX's dynamic range means that a pair of them, driven by up to 1000Wpc of amplification, will be capable of driving a large listening room of 8580 cubic feet volume to realistically high sound levels of about 110dB. That dynamic range should be available over a wide frequency range, and deliverable without distortion or compression down to a low-frequency extreme of, typically, 25Hz or below.

An accurate tonal balance is mandatory for a speaker when such high sound levels are possibleóand its price is taken into consideration! A rough, uneven frequency response quickly becomes hard and fatiguing at increasingly high volume levels. Likewise, high levels should go hand in hand with low distortion, which will help maintain tonal integrity and clarity over a wide dynamic range. High standards are also expected for stereo imaging performance. Even though the MAXX is a large speaker, its designer must make it "appear" acoustically small at higher frequencies, to maintain stable, precise image focus.

Meeting all of these requirements is no trivial engineering task.

Design and build
The MAXX's five drive-units are arranged in a three-way configuration. Two Focal drivers handle the bass, working in a common volume. As in the SLAMM, they're of different sizes: 10" and 12" (in the X-1, 12" and 15"). These are tuned to a low 23Hz by a 12.2"-deep, 5"-diameter port on the rear panel, midway between the two drivers. The effective bandwidth of this section is 20-200Hz. Mid and treble ranges are handled by the separate head-unit enclosure's time-aligned, three-way vertical driver array.. This is equipped with a central, 1" Focal tweeter flanked by a pair of 7" ScanSpeak midrange drivers. These cover 200Hz-2kHz; the tweeter covers 2kHz-22kHz.

Wilson has allowed for fine adjustment of tonal balance to accommodate room placement and, to a lesser degree, the variations in system sound that result from different combinations of source and amplification components and cables. These adjustments are generally left in the hands of the Wilson dealer, and are made via the relatively small Caddock metal-film power resistors used for mid- and treble-driver protection. These are bolted to a heatsink and are accessible under an alloy coverplate on the back of the head module. Independent ±0.5, ±1, and 1.5dB adjustments are possible for the mid and treble sections. In case of gross overload, these resistors go harmlessly open-circuit and are easily replaced, even if they do cost much more than an ordinary fuse. Fuses have complex thermal behavior that can be audible; the Caddocks remain sonically transparent until they fail.

Enclosing a volume of 3.88 cubic feet, the MAXX's bass bin is reflex-loaded, using a fairly well-damped, room-matched alignment. The large port will sustain the system's full power bandwidth and power handling. The cabinet is made of ultra-high-density phenolic bonded laminate, with the interior extensively cross-braced in all planes by high-density MDF panels. The result is an exceedingly rigid enclosure of minimal flexural resonance and stray acoustic output. The review samples came finished in an immaculate high-gloss, black-graphite metallic lacquer.

Secured to the floor by heavy-duty, hardened-steel spikes, the bass enclosure forms a rigid, stable, high-mass platform for the head unit. This is a monolithic structureóthe Grand SLAMM's was in three partsóoptimized with regard to local reflections and diffractions. The head unit's drive-unit array forms a focused arc, with the tweeter correctly displaced behind the radiating planes of the midrange drivers. The array itself is recessed relative to the bass section.

The head unit is also built of very-high-density phenolic panels, and as a result is exceedingly inert and rigid, exhibiting a fine combination of stray-resonance damping and stiffness. Three-point coupling is used between the upper and lower enclosures, helping to uncouple higher-frequency energy pathways without the imprecision of elastic or similar polymeric decoupling components.

Footnote 2: See Wes Phillips' review in the October 1995 issue of Stereophile (Vol.19 No.10).

Buried in the plinth, below and integral to the bass enclosure, the crossover network is potted in a cured-resin block that provides thermal stability and an almost complete lack of coupled vibration. The crossover design was not accessible, though I'm told the inductors are air-core, with selected polypropylene capacitors. Electrical connection is via a single set of gold-plated WBT binding posts with the 4mm entry blanked off, and is thus suited to either bare wire or spade-terminated cables, preferably the latter.

Speakers in this performance category tend to be large and heavy, and the MAXX is no exception. Each enclosure weighs 400 lbs and is 63" tall, 17" wide, and 22" deep. However, the use of the separate head unit means that the effective acoustic width at higher frequencies is barely 8", which holds out much promise for fine stereo image formation.

Wilson claims a somewhat lower sensitivity, 92dB/W, than the X-1's 95dB. In amplifierspeak, that means a doubling of the necessary amplifier power to achieve the same effective loudness. While the X-1 offers a reasonable 8 ohm load, the new MAXX admits to a more demanding minimum of 3 ohms, which might prove too much for some tube amplifiers, even high-power ones, to bear.

Like other Wilson products, the MAXX is sold with a 5-year warranty.

Delivery and installation
The total shipping weight of a pair of MAXXes, delivered in four large crates, is 1100 lbs! You need to allow up to a day, and have strong hands and backs available, to get the speakers into position. The bass bins are the largest cabinet sections. Once unpacked, they're left fitted with temporary heavy-duty industrial casters, with which they can be wheeled into place. The three-driver head enclosures are packed separately and need fitting with the support interface spikes and the stepped plates of hardened steel. This combination results in a precise three-point contact between the enclosures.

Different lengths of plate and spike help align the optimum acoustic axis to the listener, regardless of distance and ear height. While this aspect is relatively uncritical for a speaker with a mid-treble section at approximately seated ear height, the primary axis of a speaker as tall as the MAXX is must be directed down toward the listener. The resulting geometry insists that, for the very best performance, a variable head alignment is essential. By controlling the effective center of rotation, a measure of time alignment is also maintained throughout the range of adjustment.

Once the upper enclosures are in place, and adjusted by ear and according to the guide provided, they are stabilized by three-point-contact nylon-tipped locking screws to the sides—a distinctive feature of both this and the Grand SLAMM. Two cable sets terminated with spade connectors come up through the bass enclosure to supply midrange and treble to the appropriate WBT binding posts. Adjacent to these terminals are the cover plates for the protection and voicing elements.

Initial placement involves experimentation with both speaker and listener positions, the aim being to find the optimum combination of extension, overall balance, and "tune-playing" consistency at low frequencies. There are two possibilities: In large areas, the speakers can be placed virtually in free space; their positions relative to the side walls are then of little importance. In smaller rooms, side-wall symmetry is more important, as is moderate lateral diffusion—bookcases and the like—in the vicinity of the speakers. Ultimately, the enclosures will be critically positioned with respect to the side walls to help achieve the widest, most focused stereo image and the most natural timbre.

When this fine-tuning has been completed, at least two people are needed to substitute the adjusted spiked feet for the wheels, taking great care not to move the speakers off the established reference positions. Micro-tuning of timbre via the protection resistors will put that final gloss on the MAXX's overall in-room balance.

Sound
I found the MAXX, as delivered, to be a tad rich and bass-heavy for a European room built of solid brick, though I suspect it would be near perfection for US rooms with typical drywall construction. Early in the review process, in fact, I began to feel that this speaker's available power in the bass was likely to be more suited to a room even larger than mine. Usually in my room, speakers are placed around 1m from the wall behind them. With the MAXXes, this resulted in overpowering bass and insufficient tune-playing performance. Further experimentation with mid and treble levels was pointless, as it was obvious that the MAXX's low-frequency interaction with the room had to be addressed first.

With careful trial and error using known recordings, fine-tuning of the speaker and listener position over a period of 12 hours continued to give significant gains in performance. In the end, I needed no absorbers or bass traps.

Early doubts about tonal balanceódim or brightówere almost entirely resolved by placement tuning. As the speaker settled in, I became accustomed to the mildly different room sound the MAXX generates. (By "different" I mean the particular energy signature heard in the reverberant sound generated by a D'Appolito driver configuration when compared with the more usual single mid-unit placed below a tweeter.) I began to appreciate the Wilson's major strengthsóin my opinion, the MAXX's performance will probably be limited only by the installation and the matching system.

Concerning the available adjustment, the MAXX's inner integrity of tonal balance was so great that very small changes in user adjustment for the mid and treble sections proved to deliver near-magical shifts in speed, integration, and perspective. Such shiftsóeffected via those fusible protection resistorsóare clearly possible without impairing the sound's primary structure. In the hands of a skilled installer, such tuning will allow the MAXX to advance to a higher level of performance in the user's listening room. For the record, the midrange protection resistor had been set in production at 5.7 ohms, while the high-frequency section was set at 4.2 ohms. I finally chose 5.3 ohms for the mid and 3.7 ohms for the treble; these small differences were truly worthwhile.

When used in my room and partnered by up-to-date amplification, the MAXX came damn close to the overall performance of the X-1/Grand SLAMM. In absolute terms there was a shade less attack, although some might say the MAXX sounded, thankfully, more politeóthe SLAMM can sound outspoken on occasion. Some of the SLAMM's gut-wrenching low-frequency grip was absent, though debate could continue as to the degree of differenceóthe MAXX's low-frequency range was still close to the state of the art. But the Mk.1 SLAMM's sense of immediacy, of edge-of-the-seat excitementósometimes even of a mildly restless natureóhas been successfully moderated in the Mk.2. That more balanced sound was present in the MAXX as well.

Interestingly, much of this speaker's sound quality seems to work by controlled understatement. Its many accomplishments were less a matter of in-your-face obviousness than a sense of poise, overall balance, and inner grace. Time and time again, these brought substance and power to the sound reproduction.

Many big speakers sound sufficiently large only when played loud. But the MAXXólike another favorite of mine, Wilson's WITT 2ómanaged to sound generously proportioned even at moderate sound levels or at normal conversational levels; the bass lines still worked well. Increasing the volume simply increased the impact and bass extension. An inherent smoothness, also associated with this natural tonality, was clearly voiced throughout the frequency range. The MAXX could be played very, very loud indeed.

Using peak-level monitoring equipment, I confirmed a program clipping point at 970Wpc for the Krell FPB 650M amplifiers driving the MAXX. Even at that final point, however, there was no unpleasant hardening, brittleness, compression, or related distortion audible from the speaker. High powers were handled with consummate aural ease.

As I write, I'm listening to the opening of the live Pink Floyd album, Pulse (Columbia C2K 67065), and the MAXX is showing just what it can do. The sense of the live arena, the power and weight of both the PA stack and the arena ambience, is wholly appropriate. Stadium rock is full-blooded, even theatrical in dimension, and there's nothing mean about the scale of this soundstage. A sense of presence and air floats over, with, and beyond the image, conveying atmosphere and a feeling of actually being at the eventóyet there's no false glaze or related artifice.

In this respect, the MAXX showed remarkable subtlety. Likewise, there was an impressive and satisfying transparency, achieved (one imagines) by an iron build quality and an inner balance that was close to perfect; this transparency was certainly not down to a short-term exaggeration of the high-frequency register, as is so often the case with other speakers. And that transparency ran deepóan aspect held not just in isolated spotlit areas, but over a very wide frequency range.

Complementing the transparency were finely developed perspectives. Rarely does a loudspeaker at any price manage to hold all the strands and harmonic sounds of an orchestra in such a well-judged balance that focus is retained right into the far depth planes. Amazingly deep stereo images were possible, and it was rare that the physical location of the speakers intruded on the outstanding image performance. That image was certainly presented higher than usualóthe performers were standing rather than sittingówhile in the case of an orchestra, the performers were up on stage rather than down in the pit.

This speaker was by no means perfectly uncolored. In fact, it sounded less analytically neutral than a Mk.2 X-1/Grand SLAMM, never mind a top-of-the-line Thiel. On first listening I could hear a trace of the drivers' mechanical origins; for example, the carbon/resin matrix diaphragms of the midrange units. There was a softened, rounded, near-boxy character that I judged a coloration, and that would be foreign to a BBC monitor or a fine electrostatic.

Yet, mysteriously, the MAXX did not suffer in consequence. I've never heard this choice of driver sound so well-behaved, so transparent, so self-effacing, so easy on the ears as it did in this system alignment. There was no roughness or congestion associated with the midrange, where it played so smoothly that the mild coloration signature was quickly forgotten in normal use. Analytical discussion is important when things go wrong; when all goes well, analytical niceties are of passing interest only.

Notwithstanding, there was a trace of coloration in the upper bass, probably associated with the enclosure's bass-reflex designóa whiff of "inside the cabinet" sound emerged from the port. But, again, this was nowhere near high enough in level to disturb the overall blend or the overall attainment. Once again, this aspect of the speaker's presentation was soon forgotten as the system and I became better acquainted.

In other incarnations, this choice of tweeter can sound a little abrasive in its last half octave of audible bandwidth. Potentially merciless on inferior or grainy program and sources, its overall performance, particularly in terms of transparency and dynamics, still marks it as the high-frequency driver of choice for many high-end designers. But, remarkably, I heard almost no trace of that familiar if subtle Focal zing in the MAXX's highest treble. The MAXX had the nicest treble alignment yet of David Wilson's designs.

The MAXX was happy with a very wide range of music. Despite its powerful, extended bass, it was free of chestiness or bloom on vocals, and showed outstanding resolution and articulation on solo and choral sections, from grand opera and great symphonies to intimate rock or folk ballads.

With such a wide bandwidth, the sense of pace was understandably more measured than with smaller models, though the music's "timebase" was remarkably steady. Rhythm was conveyed well; tracks swung with the correct syncopation, while subtleties of percussion and syncopation were beautifully brought out. Dynamics were finely scaled, with no sudden rush to aggression as the system was driven hard. Dynamics sounded a little more restrainedósome might say more "relaxed"óthan the SLAMM's. In practice, it was easy to get used to the MAXX's particular blend of pace and dynamics, but ultimately I'd have to say that it suited classical and jazz a bit better than frenetic rock.

Early Joni Mitchell sounded remarkable. Blue (Reprise 2038-2) was reproduced with great expression and near-perfect piano accompaniment, while Mingus (Asylum 505-2) was delivered with convincing atmosphere and startlingly natural dynamics. Rickie Lee Jones' "Coolsville," from her eponymous first album (Warner Bros. 3296-2), was more than a trackóit was a music performance in its own right, of renewed power and involvement.

Cathedral organ was almost more than impressive. The MAXX could growl and roar with assured authority in the bass, but it also had no problem at all with theme and counterpoint, or with complex textures in the midband. Some speakers warp the timbres of the smaller organ pipes, rendering them too reedy. Not so the MAXX, which held onto that sweeter, more airy sound so characteristic of the live instrument. Complex organ scores frequently sound congested, a trait avoided by the MAXX. It had an almost uncanny knack of holding on to fine detail and distinct instrumental lines, no matter how rough the going.

In my experience, few speakers can play a major symphony in its entirety without some questionable moments. Sometimes, the use of sufficiently high volume levels to get good clarity in the quiet sections results in an obvious strain in the later tutti passagesóor, worse still, mechanical overload in a flat-out climax. Such concerns can add unwanted tension to the replay. The MAXX's delivery was so capable that it inspired confidence and trust. I simply stopped worrying and let composer and orchestra take the strain.

That confidence allowed my auditioning of the MAXX to transform itself from a commissioned task into one of sheer musical pleasure. The magnificent staging of two-channel stereo, the rewarding clarity, and the exceptional bandwidth and purity all helped to give me hundreds of hours of fatigue-free aural reward.

Conclusions
Living with the Wilson Audio MAXX was an experience I wouldn't have missed. I can't say that it represents perfection or is totally accurate, but it certainly presented a convincing approach to musical performance on a thrilling scale. Mahler's Symphony 8, the "Symphony of a Thousand," really justified its nickname when replayed on the MAXX.

This speaker works almost by understatement, without any "hi-fi" artificiality or exaggeration. For this, it is all the more remarkable. Devoid of hardness, constant in character and quality at virtually any listening level, the MAXX breathes control, authority, linearity, and stability. Stereo images are sumptuous, wondrously deep, velvet-textured, spacious, broad, and finely focused. Dynamics sounded wholly natural; string quartet and solo piano could hold their own with jazz and rock bands. The sound was self-evidently one of purity and low distortion, and the measurements bear this out.

The measurements were generally very good to excellent: the averaged and off-axis responses, the very wide frequency range, the low distortion and high power capacity. And the build quality is superb. I recommend detaching the upper grilles (at least) for critical listening, and hope that Wilson will supply alternative, open-cell foam slabs for those who want them.

Installation in my room proved problematical in terms of successfully dealing with what the measurements subsequently quantified as significant lift in the midbass. The advice of a skilled dealer, and perhaps a room-acoustics analyst, should be sought concerning the MAXX's suitability for certain locations. Compatibility is an important issue. It became abundantly clear that, for the best results, you'll need lusty amplification and heavy-duty audiophile speaker cable, which will add to the cost. Tube amps are ruled out.

But when properly installed and run, the Wilson Audio MAXX represents one of those great experiences in music reproduction. Its sound quality is truly satisfyingóI never tired of it throughout 150 hours of critical listening. I wish it could have been more, but copy deadlines intervened!

Notwithstanding some minor reservations, the MAXX is a remarkable achievementóa musical instrument in its own right. Buying a pair of MAXXes will be more like choosing a fine piano than a hi-fi component. It is wholeheartedly recommended. For those who care about such things: In my view, my suggested classification of the MAXX as "Class A (Full-Range)" in Stereophile's "Recommended Components" will not endure much dissent.

Description: Three-way, five-driver, reflex-loaded floorstanding loudspeaker system. Tone controls: ±0.5dB, ±1dB, and 1.5dB adjustments of mid and treble sections via power-resistor selection.
Drive-units: 1" inverted-dome tweeter, two 7" carbon-fiber-cone midrange drivers, 10" and 12" pulp-cone woofers.
Crossover frequencies: 200Hz, 2kHz, 22kHz. Port tuning frequency: 23Hz. Frequency response: 20Hz-21kHz, -3dB.
Minimum impedance: 3 ohms.
Sensitivity: 92dB/2.83V/m.
Dimensions: 63" (1600mm) H by 17" (430mm) W by 22" (560mm) D. Weight: 400 lbs each, net; 1100 lbs, both, shipping.
Serial numbers of units reviewed: Not noted.
Price: $38,900/pair.
Approximate number of dealers: 15.
Warranty: 5 years.
Manufacturer: Wilson Audio Specialties, 2233 Mountain Vista Lane, Provo, UT 84606. Tel: (801) 377-2233. Fax: (801) 377-2282.

Sidebar 3: Measurements

Taking account of the system height and the mike position, the MAXX's sensitivity was close to specification: nominally 91dB in the aurally most sensitive range, perhaps 92dB in the mid and lower mid. This sensitivity is well above average, and is comparable with the WATT 5's.

For powerful, current-capable amplifiers, this speaker's high power handling of around 500W peak program means that seriously loud in-room sound levels of 112dB are possibleóeven a few dB more, if the MAXX is partnered with a still more powerful amp (and discretion is used). Some reassurance is given by the resistor "fuses" in the signal paths of the mid and treble units.

A health warning accompanies the higher-than-usual sensitivity: namely, the measurably difficult, amplifier-taxing load impedance. With some precision I got a minimum value of 2.2 ohms in the near-peak spectral power band of the lower midrange (fig.1). In contrast to the rather amplifier-friendly SLAMM and WITT, this more or less rules out tubed amplifiers.

Fig.1 Wilson MAXX, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

In theory, even a 4 ohm load should not fall below 3.2 ohms, and although the MAXX's rear-panel label does admit to a "4 ohm" load impedance, one could legitimately call this speaker a 3 ohm load. In this light the sensitivity doesn't look so good; the true output for a real, as opposed to a "8 ohm" watt, is in fact closer to 87-88dB.

The load variation will certainly stretch the weaker amplifiers, while good, low-resistance speaker cable will also form a necessary part of the investment. Given the price of the speaker, most sensible, appropriate solid-state amplifier choices, from Mark Levinson to Krell, will have sufficient current capabilityóthough I sometimes feel that even these hearty beasts can sound still lighter on their feet when stressed less heavily than this.

Given that load impedance is a significant criterion for a speaker, the MAXX's minima indicate a degree of struggle on the part of the designer. The MAXX is not alone in this, of course; many of the Thiels also dip low, the Apogees were notorious for a combination of low sensitivity and low impedance, and I found a 2.8 ohm minimum, also in the main power band, when I measured B&W's Nautilus.

The quest for high sensitivity is all very well, but in my view it should not be accomplished at the expense of undue peak current draw. If you ever felt that the peak current criteria for big amplifiers were pure indulgence, consider a 1000W amplifier momentarily clipped into a MAXX. Worst case, the speaker will draw a massive ±57A.

It's also been shown that more complex program-related signals can draw 20-30% more current than this. Think of the demands made on cables and connectors under such conditions.

Arguing in defense of the MAXX, the impedance dip was only a third of an octave wide, after which the nominal value settled at, typically, 4 ohms over the dominant part of the frequency range. The electrical phase angle was also quite low. In-box resonance for the driver pair was approximately 48Hz, guaranteeing "prime" bass down to 40Hz, even before the bass port begins to extend the low range. The port resonance was a low 22Hz, promising reinforcement down to 18Hz, depending on room-loading conditions.

Measuring the system response on-axis gave quite a lot of information about the speaker, even though this system's size and weight meant that some measurement difficulties were inevitable. The resultant graphs are my best attempt at conveying the acoustic output; full, free-field data would be still more accurate. (Measurements were made for the speaker with the chosen "review" resistors in place.)

Fig.2 shows the main responseóa composite of low-frequency nearfield and reasonably well-gated axial measurementóthe output was seen to have several dB of bass lift, set low enough so as not to injure the tonal balance or neutrality of the midrange, but sufficient in power to have forced me to find a new listening position. In absolute terms, I did find the MAXX to have extended bassóalmost flat to 25Hz, -3dB at 20Hzóand, given room gain and a suitable environment, worthwhile bass to an absolute 18Hz or 19Hz limit: infrasonic subwoofer territory.

Fig.2 Wilson MAXX, anechoic response on reference axis at 1.4m, with individual woofer, midrange, and tweeter responses and estimate of overall LF response plotted below 200Hz.


Overall, the MAXX met reasonable ±3dB limits from 70Hz to 15kHz and was -6dB at 18Hz and 25kHz, though these figures do not really convey the smooth effect for the overall output delivered to a room. The primary midrange is very flat, meeting ±1.5dB limits from 90Hz to 900Hz. The upper mid has a mild plateau-lift on-axis, perhaps averaging +1.5dB, while beyond 2kHz the treble was mildly depressed to a similar degree, which may lend a touch of "distance" and perspective. As far as could be checked out, pair matching was better than ±0.7dB in the critical range of 200Hz-12kHz, which is a fine result.

The high treble has the usual Focal on-axis "kick," +7dB at 16-17kHz. Fortunately for most of us, this peak is placed near the edge of audibility; however, it might just be a little troublesome for younger, keener-eared audiophiles, because the tweeter in the MAXX is intended to directly face the listener. In the WATT and WITT, the treble unit is set at something of an angle, ameliorating the effect of this narrow, axially directed peak.

Fig.2 also shows acoustic crossover responses. Wilson speakers often show surprising overlaps between the drivers, yet the overall output is generally well-integrated. Take the bass section, which extends to perhaps 300 or 400Hz: there is a notch between 800Hz and 1kHz, with then a narrow directivity peak, almost a resonance, at 1.8kHz. The peak at 1.8kHz was only 12dB down on the main response, and lies underneath the treble passband.

Equally fascinating was the behavior of the tweeter, which almost meets the output of the bass units. It was only -6dB at 1.4kHz, technically considered rather low for a 1" unit with a " voice-coil. I checked out the possible distortion later in the report to confirm the viability of this aspect of the design. Finally, the midrange units nominally run from 200Hz to 2kHz and kind of fill in the gap.

Stereophile's practice is to average the forward response graphs over a moderate angle. Fig.3 shows the MAXX's response, 1/3-octave-averaged from 200Hz to 200kHz, for the 0 degrees, 15 degrees lateral, and 15 degrees vertical frequency responses. This graph reveals good off-axis control and confirms the value of the main axial reference response in fig.2.

Fig.3 Wilson MAXX, anechoic response on reference axis at 1.4m, averaged across ±15 degrees solid angle.


Wilson's older, open-cell grilles more or less defied measurement. Not so the new type. I was shocked to find how audible its effects were, and the response-error graph (fig.4) bears this out. A cross-reflection path is presented to the tweeter, which adds variations to the response of up to +4.5dB and -2dB, right up to 20kHz. The grille effect is audible as an almost "ringing" quality to the treble timbre.

Fig.4 Wilson MAXX, effect of grille (5dB/vertical div.).

Nearfield measurements (fig.5) revealed the port's broadly damped output to be centered on 22Hz, with -3dB points at 14Hz and 55Hz. Clearly, the alignment was not maximally flat, and the port had significant output up to 70Hz, as the insertion of a foam plug would testify (see later). Some stray output was present up to 500H, but in reality, at probably -26dB relative to the primary response at the listening position, it is of little consequence. The right-hand trace in fig.5 is the nearfield response of the woofers. The port null can be seen at 22Hz, and the drivers cover the broad bandpass from 40Hz to 200Hz.

Fig.5 Wilson MAXX, individual nearfield responses of (from left to right): port and woofers. The respective levels are plotted in the ratio of the square roots of the radiating areas.


With respect to the way in which the speaker's response changes with listening height, the midband region changes quickly off-axis, due to the significant vertical separation between the pair of midrange drivers. Even so, any change was minimal over a ±7.5 degrees window, the worst-case difference being 6dB from 700Hz to 2kHz. The wisdom of the slight mid lift seen on-axis is apparent. For the speaker to "sound" correct, the forward "energy" must be in balance. Over a 30 degrees vertical window, the MAXX's midrange output averages to flat uniformity.

In the horizontal plane (fig.6), the MAXX was very well behaved up to 10kHz, with no unwanted peaks developing, and, if anything, a still smoother balance at moderate off-axis angles. Even at 30 degrees off-axis, the response held within 3dB of the reference up to 12kHzóa fine result. While the speaker's analytical ability clearly directs the listener to a "sweet spot," in practice this wasn't all that critical, and very good results were also obtained over a wider spread. In large rooms, several persons could share a good measure of the performance.

Fig.6 Wilson MAXX, lateral response family, normalized to response on tweeter axis, from back to front: differences in response 60 degrees-15 degrees off-axis; reference response; differences in response 15 degrees-60 degrees off-axis.


The room-averaged response (fig.7) is a summary of two speaker positions, eight microphone positions, and a total of 64 readings. While the upper range will naturally roll off in a measurement like this, as the room's increased HF absorptivity, acting in concert with the natural directivity of the tweeter, dulls the high treble, the resultant graph should reveal the speaker's full bass extension plus a good idea of its uniformity of output up to 7kHz or so. The MAXX's in-room response was impressively smooth from 100Hz to 6kHz, meeting ±2dB limits. The result was normal beyond 6kHz, if with some clear evidence of the high peak lingering on at a subdued level.

Fig.7 Wilson MAXX, 1/3-octave, spatially averaged response in MC's listening room


What is undeniably clear in fig.7 is the MAXX's bass lift. Yes, the speaker does extend down to a very impressive (in my room) 24Hz and is still effective at 20Hz, but the midbass is boosted by an average of 4dB—a bit much for average sized, closed-plan rooms of solid construction. Experimenting with a push-fit, soft-foam liner " thick and 5" deep placed in the port tube helped moderate the bass. In larger rooms than mine <ie, more than 4235 cubic feet), experience suggests that the MAXX's bass-power level will be fine.

The X-1/Grand SLAMM excels at low distortion, and the MAXX comes a close second to that twice-as-expensive speaker system. At average listening levels (around 86dB spl), the distortion was typically -60dB, or 0.1% from 200Hz up. Impressive. At 300Hz I recorded -70dB of second harmonic and -75dB of third (Table 1). At 90dB spl, at just under an 8 ohm/watt of input (or 2 "real" watts), the MAXX measured around 0.3% below 150Hz, and at higher frequencies averaged -57dB of second harmonic and -65dB of the more potentially damaging thirdóagain, excellent results. The good control of third harmonic at 2kHz was significant, and a tough point for this tweeter. It passed the test. Amazingly, even at 20Hz the distortion was held to 1%, -40dB, predominantly second harmonic. At 40Hz it was better than 0.3%.

Table 1 Wilson MAXX, Harmonic Distortion vs SPL

fHz	86dB		90dB		100dB		106dB
	Distortion (dB)		Distortion (dB)		Distortion (dB)		Distortion (dB)
	2nd	3rd	2nd	3rd	2nd	3rd	2nd	3rd
20	ó	ó	-40	-40	-27	-26	-25	-27
25	ó	ó	-42	-42	-32	-36	-32	-26
30	ó	ó	-47	-48	-45	-43	-48	-43
50	ó	ó	-55	-57	-60	-62	-42	-51
100	-58	-73	-50	-55	-42	-51	-42	-55
500	-68	-73	-60	-68	-52	-58	N/A	N/A
1k	-63	-76	-58	-74	-42	-52	N/A	N/A
2k	-58	-63	-50	-62	-40	-58	N/A	N/A
5k	-62	-69	-57	-66	-39	-64	N/A	N/A
10k	ó	ó	-58	N/A	-45	N/A	N/A	N/A

I donned earplugs and moved to a louder, 100dB continuous level. From 30Hz to 100Hz the distortion average was still -50dB. Excellent! In the upper range, third harmonic remained tidy, averaging -56dB. While second harmonic was a little greater, it was very fair at, typically, -43dB, or almost 0.7%.

Leaving the upper range safe from overload, I drove the bass system to the practical power limit. At 106dB it still averaged 1% of second harmonic and 0.3% of third, both down to 30Hz. At 25Hz I got -32dB (2.4%) of second harmonic and -26dB of third (5%)óonly just audible at this low frequency. A true power sinewave of 140Wóequivalent to full-power orchestral bassówas sustained at 30Hz and remained tolerably pure.

Taken overall, the distortion performance was exceptionally good over the entire bandwidth. Dynamic range and dynamic linearity met the high expectations for a speaker of this engineering profile and price.

The physical structure is so well controlled that checks using an accelerometer revealed little of interest in terms of cabinet vibration. There was negligible coloration from this source.

The MAXX's step response (fig.8) was complicated by the 17kHz treble peak, which intruded at the start. Due to the delay paths to the microphone, not too much I should be read into this graph. Above 300Hz, the speaker's output had low phase shift with frequency. For the broadband energy/time response, both the unweighted (fig.9) and the Blackman/Harris weighted results (fig.10) were impressive for uniformity of decay rate, though I suspect the residual output from the bass system in the lower treble will slow the visible decay rate.

Fig.8 Wilson MAXX, step response on tweeter axis at 1.4m (5ms time window, 20kHz bandwidth).


Fig.9 Wilson MAXX, Energy-Time Curve on tweeter axis, unwindowed (5ms time window).


Fig.10 Wilson MAXX, Energy-Time Curve on tweeter axis, windowed with Blackman/Harris function (5ms time window).


For longer-term decay behavior, the waterfall graph using 10dB/div. scaling and 0.2ms decay filtering (fig.11) showed a complex field due to the driver overlap, but with no dominant features save the nearly inaudible treble resonance at 17kHz (the clean "ridge" visible in this graph). A good idea of the MAXX's transient attack is given by fig.12, which shows good phase integrity from 500Hz to 16kHz, and fast leading-edge decay. This fine performance was borne out by the listening tests.—Martin Colloms

Fig.11 Wilson MAXX, cumulative spectral-decay plot at 50" (0.2ms risetime).



Fig.12 Wilson MAXX, cumulative spectral-decay plot at 50" (0.1ms risetime).