The Wilson Audio Specialties Alexx V is the biggest, heaviest, most expensive loudspeaker I’ve had in my listening room. It replaces the original Alexx in Wilson’s lineup; Michael Fremer reviewed the earlier Alexx,1 bought it, and owned it until replacing it recently with the Wilson Chronosonic XVX.
The V in the name—Alexx V—isn’t the Roman number five; rather, it’s a reference to Wilson’s most recent proprietary composite material, “V.” But more is new here than a new material. Wilson has recast its second-largest regular-production speaker along the lines of its largest, the Chronosonic XVX.2 The similarity is most obvious in the opengantry design that the new Alexx inherited from the XVX. Wilson claims—and I believe—that this improves the sound because pressure waves were trapped by the semi-enclosed areas enfolded by the original Alexx’s solid-sided gantry. The new design also allows for somewhat finer adjustment of the higher-frequency drivers: The tweeter can now be adjusted to within1/16 “, which corresponds to less than 5μs of travel time for sound—surely below the ear’s time-resolution.
Wilson has long put much stock in the composite materials they make their cabinets from. X-Material, the primary material used in Wilson cabinets, is “extremely monotonic and damped in its response,” according to Wilson marketing materials. I’m not sure what “monotonic” means in this context—perhaps that the energy it absorbs is broadband, so it doesn’t impose specific colorations on the sound. (Stereophile’s measurements over the years have found Wilson’s X-Material cabinets to be admirably free from resonant energy.) The S-Material, which is used for the company’s front baffles, “provides a neutral and natural surface from which music can launch,” according to Wilson literature. Why does a front baffle need to have different properties than the rest of the speaker cabinet? I’m not sure; it could be as simple as being easier to machine, or engineered to hold screws better for easier, more permanent driver-mounting.3
The new V-Material, which is used where two parts of the cabinet come together, “behaves like a vibration absorber,” according to Wilson. It is used in the top panel of the woofer cabinet, where the objective, clearly, is to keep vibrations from the woofer cabinet from reaching the gantry and the lowest gantry-mounted driver. Wilson also uses the V-Material in its new, vibration-absorbing footers, which are installed on these Alexx V’s and available for other Wilson models.
Wilson invents whole new composites to endow its cabinets with the desired properties, but when it comes to driver materials—the cones and domes at least—Wilson is old-school.4 The Alexx V’s tweeter dome is doped silk. The midrange drivers are described as “doped paper pulp.” Woofers are “hard paper pulp.” I asked Daryl Wilson to explain. “Hard paper pulp,” he told me, “indicates a compression process that hardens the materials used. Doped paper pulp indicates a sealant used on the cone that is an additional step in the build process. The different drivers we use in different applications have unique mixtures of organic material, and those unique materials used are based on the suitability for the bandpass of the driver’s application.” No diamond, beryllium, or carbon fiber in sight—at least not in the finished product.
“Visitors to Wilson Audio have been astounded by the range of driver technologies that they see, which we have sourced from all over the world for evaluation. These include beryllium, aluminum, diamond, ceramic, carbon fiber, etc. After all the technical experimentations and an exhaustive measurement protocol has been conducted on all the drivers we have assessed, we get into the most critical evaluation parameter: Does it sound real?
1 See stereophile.com/content/wilson-audio-specialties-alexx-loudspeaker.
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2 The even bigger, twice-as-expensive WAMM Master Chronosonic is not a regular-production speaker.
3 I asked Daryl Wilson if he would provide more specific information about the properties of Wilson Audio’s proprietary materials. He kept his answer general. “The various composite enclosure materials we use have been thoughtfully and methodically fine-tuned in density and construction to manage vibration in the strategic way we have outlined (vibration isolation vs transmission).”
4 Which of course doesn’t mean that they don’t experiment with driver materials—read on.
“Some have stated that the materials we use in our selected drivers are somehow inferior because they don’t carry the buzz of the latest materials fad or exotic properties, which, in theory, should be better. For more than four decades, we have been collecting, testing, and evaluating drivers of all kinds of materials and construction. As we’ve listened to what’s available in the market and compared them to our own drivers, we are very pleased with how well our choices meet our specifications and how close to the music our deeply refined drivers bring the listener.
“At the heart of every final sonic decision we make in research and development, we ask ourselves, ‘Is this truly believable?’ and ‘Is this serving the music faithfully?’”
Perhaps the key phrase in what Daryl Wilson wrote is “which, in theory, should be better.” There are important reasons for preferring high-tech cone and dome materials. Cones should be stiff and light, and some newer materials achieve a higher ratio of stiffness to weight than old-school materials do. The tradeoff—so goes the conventional wisdom—is that cone breakup, when it comes, is violent. The question every loudspeaker designer must ask is: Which drivers behave best and sound best in the context of a particular design?
Wilson continues to use paper and silk. It also continues to research and upgrade its drivers. In the Alexx V, only one driver—the smaller midwoofer—is retained from the original Alexx. The 7″ midwoofer was developed for the XVX; it utilizes Wilson’s “QuadraMag” configuration, “which combines [four] Alnico magnets in an entirely re-imagined ‘quadrature’ geometry.” Both of the Alexx’s woofers—the 101/2 ” and the 121/2 “—were developed, Wilson says, for (or in conjunction with) the WAMM Master Chronosonic.
The tweeter is new. It “builds upon a modified version of the previous Convergent Synergy motor while embracing a re-imagined, intricate, and innovative rear-wave chamber,” which is 3D-printed in-house from (if I’m reading the literature correctly) carbon fiber.
What other things are new? The Alexx V adds a woofer port that can be situated on the front or rear panels, which is also in the XVX (and, if memory serves, the Alexandria XLF).
The V is the first Alexx to use Wilson’s own in-house capacitors. The midrange-driver housings now incorporate internal diffusers, built into the back of the cabinet; Wilson says this reduces the settling time, which makes sense. The crossover has been tweaked to make the V a little more amplifier friendly than its predecessor: Compared to the original Alexx, the Alexx V has gained 1dB in sensitivity, and its minimum impedance has increased by half an ohm.
A short interlude about time
Daryl Wilson told me that, long ago, his father set up some drivers in such a way that he could sit in his listening chair and adjust their relative positions by pulling a string. The elder Wilson adjusted and listened, adjusted and listened again—“and he knew it made a difference,” Daryl told me. “He didn’t understand why. Just the observation of that difference caused this whole chain of events of exploration and R&D.”
David Wilson’s observations led to the development of the complex mechanism of supports and adjustments that today, in the company’s larger speakers, allow precise adjustment of the positions of the midrange drivers and tweeter relative to each other and relative to the woofer cabinet below. Front-to-back position can be adjusted to within fractions of an inch, rake angle within a few degrees, for each of the upper-frequency drivers.
A major current of thought in the history of loudspeaker design, especially over the last two or three decades, involves the question, how much does time-alignment matter? And: Is it worth the tradeoffs? These are questions that can only be answered empirically, and the majority of speaker designers apparently have concluded that the answer to at least one of those two questions is “no.” I have long found arguments in favor of time-alignment compelling.
Designers of high-end electronic components go to great lengths to eliminate distortion, which is to say, to ensure the integrity of the musical waveform. But when that waveform reaches the loudspeaker, all hell breaks loose. Because of the crossover (and how the drivers are connected electrically), the physical layout of the drivers, and differences in how quickly the various drivers launch sound toward the listener, different frequencies arrive at the listener’s ears at different times.
A handful of speaker designers have made a serious attempt at time-aligning their speakers’ output so that the wavefronts from the various drivers arrive at the ear at the same time; classic examples are Dunlavy, Spica, Theil, and Vandersteen.5 Typically, this is achieved by using low-slope crossovers (first-order is optimal) and offsetting the drivers so that the tweeter launches its sound farther back than the midrange driver, and so on.
Such designs present major challenges. Low-slope crossovers mean drivers need to have a wide bandwidth, lest they be required to operate outside their optimal frequency range. A first-order crossover reduces output by just 6dB between, for example, 2kHz and 4kHz, so there’s substantial overlap between midrange drivers and tweeters, which aggravates interference over a wide region of overlap. What’s more, the midrange driver, which is now positioned a few inches in front of the tweeter, partially reflects the tweeter’s output.
At best, perfect alignment of wavefronts from different drivers can only happen at one point in space (unless there’s just one driver, or unless the drivers are coaxial). If you want the full, perfect effect, you need to position the speakers and your head exactly correctly, and you mustn’t move.
Presumably though—and this is important—it’s better to be close to perfect time-alignment than it is to be far away, just as it’s better to get close to ideal frequency response than to have frequencies all over the place. That assumption—that closer is better—informs the more modest time-alignment goals of many loudspeaker designers, a frequent objective of which is to simply have one driver hand off to the next in an orderly fashion: First the tweeter, then the upper midrange driver, and so on. JA has measured many loudspeakers that behave this way.
When it comes to time-alignment, it’s intuitive that high frequencies matter more than low frequencies because their rise time is much shorter. From the time you hit the switch to turn it on, a 100Hz sinewave takes 2.5ms to reach its maximum value. During that time, sound travels almost three feet. Contrast that with a 10kHz sinewave, which has a rise time of about 25μs. During the time it takes a 10kHz wave to reach its full amplitude, sound propagates about a third of an inch. Which makes me think that, when designing a loudspeaker for time-alignment, you could pretty much ignore woofers, ports, etc., and concern yourself only with lining up the tweeter and midrange drivers.
5 See, for example, the step response for the Theil CS2.4 in fig.6 at stereophile.com/content/thiel-cs24-loudspeaker-measurements. For an example of the tradeoffs of time-coincident design, see figs.4 and 5.
Complicating things further is that many loudspeakers have drivers connected in opposed polarity to facilitate optimal frequency-domain integration in the regions where the drivers overlap. Some parts of the waveform are going down when, for strict accuracy, they should be going up. Which motivates a question. Preserving the waveform means getting time (and phase) right and connecting all the drivers in the same polarity. If attaining good sound required that, then most speakers on the market would sound wrong. But they don’t. So, how much can time-alignment matter? Clearly it matters less than intuition—my intuition—would suggest.
And yet, it does matter. Relative time-shifts among drivers are clearly audible. I convinced myself of this while reviewing the Alexx V. Its setup flexibility meant I could easily move one driver forward or backward relative to the others—and listen. I found a change of half an inch or so—that’s a relative time-shift of less than 40μs—was easily audible. Surprising. I wish I could say that there was a particular arrangement of drivers where everything snapped into place, but it wasn’t like that. Maybe if I listen more, I’ll find it.
Just how concerned are the Wilson folks with time-alignment? Before he arrived to assist with the setup of the Alexx V’s, Wilson’s Peter McGrath asked me which amplifier I’d be using. Why does that matter? I wondered—and then I realized: Wilson takes phase shifts within the amplifier into account in its time-alignment calculations.
Why go to so much trouble? And what precisely is Wilson’s technical aim when it comes to time-alignment? I asked Daryl. “Over the decades, we’ve come up with very specific testing protocols. And we have in some instances very modified testing equipment to get that right. There are certain secret sauces that I have to keep confidential.” Fair enough; every chef needs a secret sauce.
It’s not my job to reverse-engineer technology to reveal corporate secrets, and I will not do so here. But there’s evidence on the record, including JA’s measurements of many Wilson speakers over decades—including, in the accompanying sidebar, the Wilson Alexx V. I’m sure Daryl Wilson won’t mind if I make some rather obvious observations on what those measurements show.
For one thing, they show that, like many other manufacturers, Wilson often uses drivers in opposed polarity—including (as I learned when I took a peek at fig.5 in the measurements sidebar) the Alexx V. Otherwise, what they show—this is my interpretation—is that what Wilson aims to achieve is similar to what other manufacturers aim to achieve—they just aim to achieve it with greater precision and more flexibility. The Wilson Alexx V allows adjustment to the nearest1/8 ” for the midwoofers and the nearest1/16 ” for the tweeter. That corresponds to intervals—the time it takes for a soundwave to travel that distance—of less than 10μs and less than 5μs, respectively. That’s at the absolute lower limit of the timescales that matter in hi-fi.
It seems that, back in the day, when Dave Wilson was pulling those strings, he concluded that driver polarity doesn’t matter (or not as much as other things) but that relative arrival time matters a great deal. Perhaps the most important thing, though—regardless of precisely what Dave Wilson decided—is that Wilson offers exquisite control over a significant setup variable.
The delivery truck arrived with two strong, friendly, helpful guys but with equipment that was inadequate to the task of getting two 500lb Alexx V’s up three steps and into my apartment. But where there’s a will there’s a way. There were some scary moments, as the crate lids—doubled up and employed as a ramp up those three steps, with foam stuffed underneath for added support—quivered and cracked. I stayed out of the way. The speakers made it up the ramp and into my apartment without a scratch.
The Alexx V’s were assembled, wired, and roughly positioned. Front-vent and rear-vent configurations were compared; front-vent was the easy winner. Once the speakers were roughed in, and after some iteration, the position of my listening chair was measured, as was the height of my ears. This information was sent to the Wilson mothership, and settings for adjusting the gantry-mounted speakers were sent back. Adjustments were made, and the settings were fine-tuned by ear—just one small tweak.
These are big speakers, profoundly full-range, but they also present a microscopic perspective.
When Peter McGrath and Chris Forman (of Innovative Audio, the local NYC Wilson dealer) were happy with the sound, we called it a day. The speakers were left on to play at a low level.
This is a big speaker, so an obvious place to start listening was with big music, music with serious scale. That means minimally produced large-scale classical music and maximally produced large-scale electronic music, with deep bass.
In the latter category, I can’t think of a better example than You’re Dead! by Flying Lotus (16/44.1 FLAC rip from CD, WARPCD256), which includes contributions from Thundercat, Kamasi Washington, Kendrick Lamar (on “Never Catch Me”), Snoop Dogg (“Dead Man’s Tetris”), ELO’s Jeff Lynne, and Herbie Hancock, among others. This is one of the more challenging albums I know of to sort out because at any given moment it spans most of the audible frequency range (and surely goes beyond it) and fills the whole soundstage with clutter. The Wilsons had little trouble sorting it out, partly by distributing it over a larger area so that all those little pieces were better separated. Put another way, the soundstage was vast, side to side, front to back—and top to bottom, and all the varied sounds were laid out on that stage in an orderly way.
I almost failed to mention that latter dimension because by this time I’d started into serious listening, I’d long acclimated, but: From my listening seat, the Alexx V’s cast their soundstage higher than any other speaker I’ve experienced here, which I suppose isn’t surprising considering that the Alexx V is tall. My chair lays me back at a comfortable angle, from which it seems natural to “look” up at the music.
The processed vocals on “Archangel,” from Untrue, the 2006 album from Burial, sounded creamy—as did the vocal on “Timeless,” the title track from the album of that name, Goldie’s 1995 debut (16/44.1 MQA/Tidal).
It had been a while since I’d listened to Selected Ambient Works 85–92 by Aphex Twin (16/44.1 FLAC/Qobuz), but, while this is a very immersive album, I don’t recall it being quite this immersive. It felt like I was floating in a sea of ambient sound. (In this two-channel configuration, the inevitable sense of the sound being “over there” never quite went away, but it is to the Alexx V’s great credit that it almost did.) Finally in this music category, upon stumbling across a piece called “Kittens” from the Underworld album Beaucoup Fish—well, how could I not play it? So I played it and loved it. What did it show me about the Alexx V? More of the same explicit clarity. Spatial separation. Profound full-rangeness.
I was having so much fun that it was hard to leave this electronic music behind. So I listened to a couple of tracks on “Music for the Jilted Generation” by The Prodigy and a couple more from Portishead. But there was work to do (this is work?) and there were other kinds of music to explore.
The third movement, “In ruhig fliessender bewegung,” of Mahler’s Symphony No.2 in C-minor (“Resurrection”) from Benjamin Zander and the Philharmonia Orchestra (24/192 ALAC, Linn Records CKD 452) was pure joy to listen to, thanks to the scale and clarity of the recording and the speakers. These big woofers reproduced bass drum and timpani in a way that was perhaps more generalized than with some speakers with smaller woofers I’ve recently experienced. (I suppose that those big woofers could need a few more watts than these monoblocks were providing—although the Pass Labs XA-60.8s’ bias meters were hardly moving; just the slightest jiggle in the loudest passages.)
My wife and son recently journeyed to Iceland, a favorite vacation destination for my family. In Reykjavik, they visited 12 Tonar, the famous record store, and paid famous Iceland prices for a gift for me of two LPs by Icelandic pianist Víkingur Ólafsson. Mozart & Contemporaries is a wonderful record, except that certain tracks were distorted, even after a trip through the Vinyl Cleaner Pro, so I set the record aside and streamed the album instead (24/192 FLAC, DG/Qobuz). I often find the sound of DG CDs unengaging, but this hi-rez stream sounded lovely. What was notable was how even the piano’s sound was from top to bottom, revealing that both the Steinway D and the Alexx V’s were behaving well. The lower notes were satisfyingly round and full, and all the notes floated in space as if emerging from a realistically sized concert grand.
I try to listen to every recording our music reviewers recommend. I can almost always see the merit—but one of this month’s jazz records stands out for its sonic quality: the David Sanford Big Band’s A Prayer for Lester Bowie. Reviewing the CD, Fred Kaplan gave it a rating of four stars for sonics. I listened to the 24/96 stream on Qobuz (24/96 FLAC, Greenleaf/Qobuz), and I’d have given it 4.5 stars: Check out the solo trumpet (Dave Douglas) that constitutes the first two-plus minutes of the title track, or the bowed bass solo that starts at the five-minute mark (soon doubled by trombones) in Dizzy Gillespie’s “Dizzy Atmosphere.” Lester Bowie was engineered by 10-time Grammy Award winner Tom Lazarus, who obviously knows where to put a microphone. This is wild, busy, radical music—difficult to engineer.
Some might fault this recording for being too even-handed, not editorial enough. Indeed, there’s not much intervention: The perspective is consistent, the solo instruments hardly spot-lit. Necessarily for an ensemble of this size, the perspective is somewhat distant. The recording has exceptional clarity—indeed, a fractal quality, whereby at any of its busiest moments, you can pick out any area of the stage and drill in by focusing your ear-brain; The music opens up, and you hear a new level of detail. The forest and the trees are recreated in my room.
I’m emphasizing this recording because it illustrates an aspect of the Alexx V that I found characteristic—and surprising: These are big speakers, profoundly full-range, but they also present a microscopic perspective.
This is my first extended listening experience with a Wilson loudspeaker. What I heard surprised me. I was not surprised that the Alexx V is very good; I’d have been shocked if it was not. What surprised me was not how good it was but how it was good.
Over the years I’ve been seriously interested in hi-fi, I’ve come to associate Wilson with emotional approachability—why else would their products have such passionate advocates? Their use of traditional driver materials—paper cones and silk domes—reinforced that stereotype in my brain: no analytical sound or harsh-sounding metal tweeters on a Wilson speaker!
There’s nothing wrong with that, but that assumption, which I held without evidence or sufficient experience, sold Wilson short. During the long audition leading up to this review, I heard nothing that would cause me to label these speakers as warm, or pretty, or endearing—no midbass emphasis, no rolled-off highs, no tweaking of the presence region (one way or the other) to accentuate the midrange or increase the sense of detail or immediacy. The Alexx V is distinguished not by any special warmth, approachability, or friendly coloration but, rather, by its evenness and consistency of tone, its ability to excavate detail effortlessly and without emphasis, and its clarity, accuracy, and naturalness of musical expression. My experience as a reviewer has taught me that those are difficult things to achieve all at once.
The Alexx V is the work of a disciplined, experienced, serious designer.
Description Multiway, bass-reflex, floorstanding loudspeaker. Drive-units: 1″ doped-silk dome tweeter in sealed enclosure; one 7″ and one 53/4 ” midwoofer with “doped paper pulp” cones; 101/2 ” and 121/2 ” woofers with “hard paper pulp” cones; front- or rear-facing rectangular port. Sensitivity: 92dB/W/m@1 kHz; Nominal impedance: 4 ohms; Minimum impedance: 2.0 ohms @250Hz. Frequency response: 20Hz–32kHz, ±3dB.
Dimensions 66″ (1676mm) H × 153/4 ” (400mm) W × 277/8 ” (708mm) D. Weight: 500lb (226.8kg) each.
Finish Cobalt Blue Satin, 19 other colors.
Serial numbers of units reviewed 0083, 0085. Made in Provo, Utah.
Approximate number of dealers: 38. Warranty: 5 years with registration.
Wilson Audio Specialties, 2233 Mountain Vista Ln.
Provo, UT 84606.
Tel: (801) 377-2233.
Because of the Alexx V’s size and bulk, I measured its performance in Jim Austin’s listening room. I used DRA Labs’ MLSSA system and a calibrated DPA 4006 microphone to measure the Wilson Audio Alexx V’s frequency response in the farfield, an Earthworks QTC-40 microphone for the nearfield and in-room responses, and Dayton Audio’s DATS V2 system to measure the speaker’s impedance.
Wilson’s Peter McGrath had adjusted the positions of the Alexx V’s tweeter and midrange modules so that their axes converged on the positions of JCA’s ears, which, with him sitting in his IKEA chair, were 34″ from the floor and 138″ from the top of each Wilson’s upper-midrange enclosure. I measured the quasi-anechoic response of the left-hand Alexx V, averaged across a 30° horizontal window centered on the position of his ear. However, the presence of early reflections from the room boundaries means that the FFT-calculated response was not valid below 1kHz or so. We therefore estimated what the microphone height from the floor would be at my usual measurement distance of 50″. This was 42″, which was level with the lower-midrange module. I took a second set of measurements with MLSSA at that microphone position.
Looking first at the Alexx V’s voltage sensitivity, my estimate of 90.8dB(B)/2.83V/m was slightly lower than the specified 92dB. However, Wilson’s specification is for 1W at 1m; with its specified impedance of 4 ohms the loudspeaker actually draws 2W from the amplifier with a 2.83V signal. As with the original Alexx, which Michael Fremer reviewed in May 2017,1 the Alexx V will play loudly with relatively few amplifier watts—or it would if its impedance were not low. My impedance measurement is shown in fig.1. The impedance magnitude (solid trace) remains between 2 and 4 ohms for almost the entire audio-band, with a minimum value of 1.9 ohms between 242Hz and 270Hz. The electrical phase angle (dotted trace) is low from the upper bass to the low treble, but there is a combination of 3 ohms magnitude and a phase angle of –39° at 53Hz that exacerbate the drive difficulty.
Using a spreadsheet prepared by Jim Austin, I calculated the effective resistance across the audioband (EPDR2) that results from the combination of magnitude and phase angle. The EPDR drops below 2 ohms over most of the midrange and mid-treble regions, with minimum values of 1 ohm between 50Hz and 64Hz, 1.15 ohms between 197Hz and 203Hz, and 1.05 ohms between 3kHz and 3.16kHz. Owners of the Alexx V need to match the speakers with amplifiers that are unfazed by very low impedances.
1 See stereophile.com/content/wilson-audio-specialties-Alexx-loudspeaker-measurements.
2 EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier’s output devices as the loudspeaker. See “Audio Power Amplifiers for Loudspeaker Loads,” JAES, Vol.42 No.9, September 1994, and stereophile.com/reference/707heavy/index.html.
I listened to all the enclosure panels with a stethoscope while I played the MLSSA test signal. The woofer bin’s heroic cabinet construction meant that I couldn’t hear any panel resonances. However, some low-level liveliness was audible with the three upper-frequency enclosures—tapping the sidewalls with my knuckles I could hear a faint “plink” with the stethoscope. Investigating this behavior with a plastic-tape accelerometer, I found some modes close to 500Hz with all three enclosures (fig.2). However, the relatively high frequency and Q (Quality Factor) of these modes and the very small radiating areas mean that this behavior will not have audible consequences.
Both woofers cover the same pass-band and cross over to the lower-midrange unit around 150Hz. That unit, in turn, appears to be crossed over to the upper midrange unit at about 750Hz. The impedance graph suggests that the large port is tuned to 20Hz, and nearfield measurements of the woofers’ outputs revealed that they each had a minimum-motion notch close to that frequency. The port’s output, again measured in the nearfield, peaked between 15 and 30Hz, but didn’t begin its upper-frequency rolloff until 65Hz. The port’s output in the midrange was well suppressed, however.
The blue trace below 300Hz in fig.3 shows the complex sum of the nearfield port, woofer, and midrange responses, taking into account their radiating areas, amplitudes, and acoustic phase angles. The small peak in the midbass is probably an artifact of the nearfield measurement technique; the Alexx V’s low frequencies don’t quite extend to the port tuning frequency, which, like the original Alexx, suggests that the woofer alignment is somewhat overdamped. Higher in frequency, the blue trace shows the Wilson’s farfield response averaged across a 30° horizontal window centered on the calculated listening axis at 50″. The small excess of energy between 1.3kHz and 2kHz is lower in amplitude than with the Alexx’s response (fig.2 in that review, see footnote 1), but there is a similar suckout above that region. Again as with the original Alexx, the suckout tends to fill in at the listening position (red trace). Other than the upper-midrange peak, the speaker’s balance is relatively even between 100Hz and 20kHz, with small peaks balanced by small dips.
It wasn’t possible to lift the Alexx V onto a wheeled dolly to allow it to be rotated for me to examine the loudspeaker’s horizontal dispersion in detail. However, the geometry of JCA’s room meant that I could move the microphone by 5° intervals up to 45° to the side of the listening axis at 50”. It appears that the Alexx V maintains its spectral balance below 15kHz up to ±15° to the sides of the measuring axis and that the on-axis suckout at 3kHz tends to fill in a little off-axis. In the vertical plane, there is a little more energy in this region as you move above the measurement axis, though the suckout deepens below that axis.
I averaged 201/10-octave–smoothed spectra, individually taken for the left and right speakers, in a rectangular grid 36″ wide by 18″ high and centered on the positions of JCA’s ears to produce the Alexx V’s spatially averaged response (fig.4, red trace). For reference, the blue trace shows the response taken under identical conditions of the Magico A5, which JCA reviewed in July 2021.3 (I have truncated the Magico’s response below 35Hz, because the plot is contaminated by subsonic noise from JCA’s apartment’s heating/ventilation system, which could not be turned off on the March morning that I performed the A5 measurements.)
On the face of things, the two speakers behave similarly between 200Hz and 10kHz, though the Alexx V has a little less energy in the midrange and a little more low-treble energy. The Magicos have greater output in the upper bass, but both types of speaker excite the low-frequency room resonances to a similar degree. The response of each speaker gently slopes down above 5kHz, which will be due to their tweeters becoming more directional as the frequency increases and to the increased absorption of the room furnishings in the treble. (What you don’t want to see with a spatially averaged in-room response is a flat treble output, which will sound excessively bright/shrill.)
In the time domain, the step response on the listening axis at 50″ (fig.5) reveals that the tweeter and lower-midrange unit are connected in positive acoustic polarity, the upper-midrange output and woofers in negative polarity. (This is identical to the polarities of the drive-units of the original Alexx, and I confirmed this by examining the individual step responses of the Alexx V drivers.) If you look closely at this graph, you can see a slight discontinuity at 3.75ms, which is due to the upper-midrange unit’s output arriving very slightly too late to smoothly blend with the negative-going decay of the tweeter’s step. Similarly, the small discontinuity just before 4ms is due to the lower-midrange unit’s step arriving slightly after the negative-going decay of the upper-midrange unit’s step. But other than those admittedly minor issues, the Alexx V’s step response is time-coherent on this axis,4 implying optimal crossover implementation.
3 See stereophile.com/content/magico-a5-loudspeaker.
I tried eliminating the first discontinuity by moving the microphone higher, but this moved the lower-midrange unit’s output farther back in time. When I lowered the height of the microphone, this resulted in a better blend of the two midrange-unit outputs but worsened the discontinuity between the tweeter and upper-midrange steps.
To be fair, the geometry of the upper-frequency drive-unit outputs had not been optimized for this relatively close microphone distance. Fig.6, therefore, shows the Alexx V’s step response at the position of JCA’s ears. (Ignore the boundary reflections after 11.5ms in the trace.) The decay of the tweeter’s step now blends smoothly with the negative-going upper-midrange step, though there is still a slight discontinuity between the two midrange steps. This suggests that the lower-midrange drive-unit should have been moved forward one notch in the gantry to give optimized time-domain performance.
Finally, the cumulative spectral-decay or waterfall plot at 50” on the listening axis (fig.7) shows a clean initial decay, but as with the original Alexx there is then some low-level hash present throughout the midrange and treble. I suspect that this behavior is due in part to early reflections from the complicated, upper-frequency drive-unit array.
Measuring a loudspeaker as large, as heavy, and as complicated as Wilson Audio’s Alexx V without access to an anechoic chamber is problematic. But that smooth, relatively even in-room response is probably what is most important when characterizing its sound quality.—John Atkinson
4 I should clear up some readers’ confusion about my use of the terms “time-coherent” and “time-coincident” with multiway loudspeakers. The latter means that the outputs of the drive-units arrive at the nominal listening/microphone position at the same time. The step response is therefore a right triangle—a vertical rise from zero with then a slow decay to the timeline—and the musical waveform will be reproduced precisely. This is very difficult to arrange—the only dynamic speakers I have measured that were truly time-coincident have been various Dunlavys, Spicas, Thiels, and Vandersteens. By “time-coherent,” I mean that the crossover’s phase shift in the crossover region and the different distances of the acoustic centers of the drive-units from the listening/microphone position are taken into account; the result is a step response where the decay of each drive-unit’s step smoothly blends with the start of the step of the drive-unit next lower in frequency. To the ear, the difference between perfect time coincidence and perfect time coherence is relatively minor.