Wilson Audio Specialties Alexx loudspeaker

Having discontinued the MAXX3 loudspeaker ($68,000/pair in 2009, when I reviewed it), Wilson Audio needed to plug the resulting gaping hole between the Alexia ($48,500/pair) and the Alexandria XLF ($210,000/pair). Company founder Dave Wilson was busy with the limited-edition WAMM Master Chronosonic loudspeaker ($685,000/pair), so son Darryl Wilson set about creating a speaker with a retail price of about $100,000/pair. The result, the Alexx, finally came in at $109,000/pair.

The Alexx shares with the Alexandria XLF Wilson's Aspherical Group Delay technology, whereby the positions of its individually enclosed midrange and treble drivers can be adjusted, precisely, to recreate a time-correct waveform at the listening position. The Alexx is thus easily recognizable as a Wilson Audio design. Incidentally, Darryl didn't design it alone: He managed a team that included Vern Credille, Wilson Audio's chief acoustical and electrical engineer, whom I met when I toured the Wilson factory in fall 2016 (footnote 1).

The Alexx looks like a smaller Alexandria XLF. Still, at 62.3" high by 15.75" wide by 26.75" deep; and weighing 452 lbs, this is a big, heavy speaker. And, like the Alexandria's, the Alexx's tall, rectangular, ported bass enclosure houses two woofers: an 10.5" and a 12.5", vs the bigger speaker's 13" and 15" cones. The smaller, upper woofer's radiation pattern at the top of its frequency range is claimed to produce a better blend with the lower limit of the lower and larger midrange driver's response (see below). The newly designed drivers with their cones of hard paper pulp replace the Alexandria's Focal-sourced "W"-material woofers. The new woofers were evolved from those developed for the Alexia, which in turn were originally designed for the WAMM.

Unlike the Alexandria's bass bin, the Alexx's is made from Wilson's X-Material, a proprietary, mineral-infused, phenolic-composite resin that's very stiff and difficult to machine. Its angled front baffle is claimed to produce better integration of the drivers' outputs in the time domain, and its sides gently taper toward the top, for a more graceful transition to the stack of tweeter and midrange housings above.

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Unlike the Alexandra's midrange-tweeter-midrange (MTM) configuration, in which two 7" midrange drivers each cover the same range of frequencies, the Alexx's four-way design divides the midband between two drive-units, a 5.75" and a 7", each driver covering a different bandwidth.

While Wilson doesn't specify the Alexx's crossover frequencies, the 7" midrange driver—the same composite pulp/fiber cone used in the Alexandria—covers the lower midrange; the 5.75" paper/pulp cone, originally used as the midrange driver of the Sabrina, covers the upper midrange. This configuration preserves the dynamic benefits of the larger midrange driver, with its robust half-roll rubber surround, while slightly extending the upper-midrange response, which relieves the tweeter of some of its former upper-midrange duties. That tweeter is a 1" Convergent Synergy dome unit of doped silk, built by Scan-Speak to Wilson's specifications; Convergent Synergy variants are now used throughout Wilson's product line.

As in the Alexandria XLF, each of the three MTM drivers occupies its own enclosure: the 7" and 5.75" midranges respectively at bottom and top, and the 1" tweeter between them (the midrange enclosures are vented). Each enclosure can be slid forward or back, and/or tilted, relative to the woofer bin. The goal, as suggested earlier, is to position the drivers for precisely simultaneous arrival at the listening position of all frequencies, and to improve frequency-domain driver integration. Protruding from the base of each midrange enclosure are three spikes—two in front, one at the rear—that sit on an aluminum step; the angle, or rake, of the enclosure, can be adjusted with spikes of various lengths. The Alexx is the first Wilson speaker with two of these steps.

The fore-and-aft position of each upper enclosure is determined and secured by where in each of two dimpled tracks the enclosure's front spikes are placed. Its rake is set with a rear spike, after which it's locked rigidly in place with large-diameter bolts. The tweeter enclosure sits on its spikes atop the housing of the 7" midrange, occupying the space within that enclosure's L shape (as viewed from the side).

Vern Credille did the complex math that determined each baffle's fore-and-aft position and rake angle, based on the listener's distance from the speakers and the height of his or her ears when seated. In the manual, Wilson supplies charts of figures that eliminate guesswork and make possible foolproof installation by the dealer.

Otherwise, the Alexx is another example of Wilson Audio's meticulous build quality: robustly braced, nonresonant enclosures of Wilson's X-Material (S-Material is used for the front baffles of the midrange enclosures); overbuilt, potted crossover networks, the wiring looms of which comprise twisted pairs, each of a specific construction, length, and twist ratio (Transparent Audio manufactures all of the Alexx's internal wiring to Wilson's specifications); and even the grille frames, which are not injection molded but machined of X-Material.

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The single pair of binding posts for connecting the entire Alexx to a power amplifier—three other pairs of binding posts, for the midrange and treble drivers, accept the spade lugs with which the crossover's wiring looms are terminated—are low on the bass bin's rear panel, but higher than on the Alexandria XLF, where they're too close to the floor for the comfort of thick, bulky speaker cables. Sometimes I wonder if speaker and amplifier makers even try to hook up their products in real-world situations.

Pairs of resistors mounted on a massive heatsink, to protect and "level tune" the tweeter and midrange drivers, are found on many Wilson speakers. On the Alexx they're conveniently placed behind a transparent panel, on a beveled surface at the back.

Setup
Wilson Audio's Peter McGrath set up the Alexxes. The speakers ended up close to where the Alexandria XLFs and other speakers have sat here, but closer than the XLFs to the front wall. McGrath did his final tuning by listening to "So Do I," from Christy Moore's This Is the Day (CD, Sony 5032552)—the same track he used to set up the Alexias in John Atkinson's listening room. Just plunked down in the approximately correct positions and still on their casters, the Alexxes' nimble sound perked up my ears. But then, McGrath's small changes in positioning produced larger-than-expected changes in Moore's voice, and in the nimbleness and clarity of the double bass.

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Once McGrath was satisfied, we used the supplied floor jack to swap casters for spikes, then experimented with the Alexx's Cross-load Flow Port System, aka XLF and borrowed from the Alexandria. This allows the port to fire from the speaker's rear or front. As with the Alexandrias in my room, having the Alexxes' ports fire to the rear produced more and better bass, despite the speakers' nearness to the wall behind them.

Sound: half the price, half as good?
What did I expect from a speaker costing about half as much as the Alexandria XLF—which, before Wilson developed the WAMM Master Chronosonic, had been the company's flagship model? With the Alexx's lack of the Alexandria's rear-firing, top-mounted supertweeter, I expected a somewhat smaller soundstage, especially in the vertical dimension, and that's what I heard. Nonetheless, the Alexxes' stage still went higher than that of many other speakers. Otherwise, I didn't know what to expect.

Going from the MAXX 3 ($68,000/pair in 2009) to the much larger, far more costly Alexandria XLF ($210,000/pair) brought with it high expectations, all of which were met. The Alexandria was an improvement in every way—especially on top, where it sounded airier, sweeter, more relaxed, and yet more detailed. Most impressive was that such a tall stack of drivers could produce a 100% coherent, three-dimensional picture from less than 8' away, while managing to sound small or grand, depending on the recording.

Time alignment of the drivers' outputs is not the end-all and be-all of speaker design, but in my experience, once you've grown accustomed to the sort of minimal-baffle, time-aligned driver arrays produced by Wilson and Vandersteen Audio, when you then hear a flat slab speaker, you hear a flat slab, especially in nearfield listening environments like mine.

Even with the music on Peter McGrath's unfamiliar setup CD, it was immediately apparent—and very surprising—to me that the Alexx significantly outperformed the Alexandria XLF in some key areas. Going from Alexandria to Alexx was like pushing a high-performance car's electronic-suspension button and going from Comfort to Sport mode. From top to bottom, the Alexx's sound was nimbler and surprisingly more transparent, particularly in the midrange, where the Alexandria can be too generous. The bottom octaves were fully developed, yet fast and precise in ways I didn't think my room could support.

As I wrote in my review of Marten's Coltrane 3 ($100,000/pair), in my room the Martens produced deeper, tighter bass than the Alexandria XLFs—or, for that matter, than any Wilson speaker I've owned. So did the Vandersteen 7s—though a speaker with a powered woofer section is a different animal.



Footnote 1: See my horizontally challenged smartphone video of the tour here.
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ARTICLE CONTENTS

COMMENTS
SpeakerScott's picture

"The Alexx shares with the Alexandria XLF Wilson's Aspherical Group Delay technology, whereby the positions of its individually enclosed midrange and treble drivers can be adjusted, precisely, to recreate a time-correct waveform at the listening position."

Would it be possible, at some point in the future reviewing a Wilson Audio speaker to measure the spot at the listening position where this is actually true? I've never once seen a review with anything remotely indicating a time domain accurate speaker. JA has accomplished it in the past with Dunlavvy and others...but never Wilson.

-Scott

John Atkinson's picture
SpeakerScott wrote:
Would it be possible, at some point in the future reviewing a Wilson Audio speaker to measure the spot at the listening position where [recreating a time-correct waveform] is actually true?

The step response calculated from the in-room measurement of the Alexx at the position of Mikey's ears that I made with the Fuzzmeasure system is not in conflict with the quasi-anechoic step response shown in fig.4, ie, tweeter and midrange units are connected in positive acoustic polarity, the woofers in negative polarity. And as I said in the review, the output of each drive-unit blends smoothly with that of the next lower in frequency. So while the Alexx's output is not time-coincident, it is time-coherent, which I feel more important.

John Atkinson
Editor, Stereophile

SpeakerScott's picture

"The step respons calculated from the in-room measurement of the Alexx at the position of Mikey's ears that I made with the Fuzzmeasure system is not in conflict with the quasi-anechoic step response shown in fig.4, ie, tweeter and midrange units are connected in positive acoustic polarity, the woofers in negative polarity."

Mr. Atkinson, this statement is a bit confusing...is there a second unpublished step response measurement in addition to figure 4? My issue is not with the performance of the system in the time domain itself, for a large format multi-driver system the measurement in figure 4 is entirely reasonable. I've measured way worse...as have you, and we've both measured better.

My issue comes from the manufacturers claim that adjusted, precisely, to recreate a time-correct waveform at the listening position..

In this case your measurements show, that after adjustment the response at the measurement location is not a correct representation of a step response.

In fact after studying the step response I may disagree with your assertion that the tweeter and midrange are in positive acoustic polarity. Notice the very short positive spike at approximately 3.75mS, in the positive direction, followed very quickly by a negative going "spike" just before 4mS. The negative going one I believe is the tweeter. As you study it, if that negative going spike wasn't there the remaining positive triangle would be the approximate shape from a 6-7" midrange driver operating over a relatively wide bandwidth. Put another way if the woofer(s), midranges and tweeter are operating over three frequency bands, how can you have two negative going spikes if two of the driver bands are supposed to be positive.

My interpretation is that the midrange is the only driver operating in positive acoustic polarity, and the woofer(s) and tweeter inverted. It is unlikely that either woofer would show the negative going risetime between 3.75 and ~3.9mS due to the low pass filters.

The fact that the midrange has such a sharp risetime and long tail indicate they are operating over widebandwidth, possibly with large amounts of overlap both acoustically and electrically which would explain the low impedance in the 500Hz to 3kHz range and the difference in on axis response 50" and 85". I would hazard a guess that had you been able to run vertical polar response measurements there would have been relatively large nulls and peeks across that bandwidth......

Again, my issue is not with the measurements themselves, but the disparity between marketing statements and measured performance.

a.wayne's picture

Never happen in the Time Domain with a reverse phase tweeter and JA 36 " height measuring technique.

John i know its 450 lbs , but I'm sure Between you, Mickey and Darrell you guys could pop this thing on its side and do a couple GP measurements on tweeter axis , no gating or splicing necessary ... :)

Want a better idea ? You could fly out to WA and do your measurements there , it would make for a great story , crap ! i can remember when SP used to do great measurement stories like that ..

Regards

John Atkinson's picture
a.wayne wrote:
Never happen in the Time Domain with a reverse phase tweeter...

The Alexx's tweeter is connected in positive acoustic polarity - see fig.4 in the review's Measurements.

John Atkinson
Editor, Stereophile

SpeakerScott's picture

I think the tweeter and woofer are negative...see my rather long winded response to Mr. Atkinson...

-Scott H.

John Atkinson's picture
SpeakerScott wrote:
I think the tweeter and woofer are negative...see my rather long winded response to Mr. Atkinson...

I am sorry but you are both wrong. You can find the impulse response of the Wilson Alexx, taken in Michael Fremer's listening room, at www.stereophile.com/content/wilson-alexx-inroom-impulse-response. You can see that the tweeter's output - the sharp spike at the beginning of the impulse - is in positive acoustic polarity.

And to confirm what I described in the text associated with fig.4 in the review, you can find the step responses of one of the midrange units and one of the woofers at www.stereophile.com/content/wilson-alexx-midwoofer-steps. The midrange unit's output is in positive polarity (like those of the tweeter and the other midrange unit), the woofer's in negative polarity.

John Atkinson
Editor, Stereophile

SpeakerScott's picture

Mr. Atkinson,

Thank you for the response and additional measurements. I think I understand better now....and now I'm even more perplexed about the time domain performance marketing claims of Wilson Audio.

The additional midrange/woofer step response measurements you provided do not adequately explain the sharp negative spike between roughly 3.5mS and 4mS in Fig. 4 of the review measurements. It's a bit difficult to see given the difference in time scale resolution (5 total mS with .5mS minor divisions vs. 50mS with 2mS minor divisions) but there is nothing in the dotted line that shows the sharp negative spike as it appears in Fig 4.

That now leads me to believe that the tweeter and one midrange are positive polarity while the woofer(s) and other midrange are negative unless you have additional measurements that would indicate the root cause.

-Scott

John Atkinson's picture
SpeakerScott wrote:
Thank you for the response and additional measurements. I think I understand better now....and now I'm even more perplexed about the time domain performance marketing claims of Wilson Audio.

You're welcome, Scott. But I owe you and a.wayne an apology, as while you were incorrect about the polarity of the Wilson's tweeter, I was also incorrect when I said that both of the midrange units were in the same polarity.

SpeakerScott wrote:
The additional midrange/woofer step response measurements you provided do not adequately explain the sharp negative spike between roughly 3.5mS and 4mS in Fig. 4 of the review measurements.

I reexamined the step responses of the 2 midrange units and have posted them at www.stereophile.com/content/wilson-alex-midrange-steps. You can see that while the output of the lower midrange unit is in positive acoustic polarity, that of the upper midrange unit is in negative polarity. So the negative-going spike that puzzles you is actually the step response of the upper midrange unit. It blends smoothly with the step responses of the tweeter and lower midrange unit to give a time-coherent output.

SpeakerScott wrote:
That now leads me to believe that the tweeter and one midrange are positive polarity while the woofer(s) and other midrange are negative unless you have additional measurements that would indicate the root cause.

You are correct and I will amend the review text accordingly.

John Atkinson
Editor, Stereophile

a.wayne's picture

Hello John,

Yes, Lazy typing on my part , I did say reverse phase , instead of out of phase, as all the drivers dont share the same phase, , I did not specify as i should if positive or negative phase and yes you are correct the tweeter is of positive polarity, but that was not what i was addressing.

BTW, Is there any reason why you still favor using gated measurements with such short reflective paths ?

With such a large complex speaker , why not measure it at WA..? we would all like to see what it looks like in the time domain.....

Regards...

John Atkinson's picture
a.wayne wrote:
yes you are correct the tweeter is of positive polarity, but that was not what i was addressing.

See my recent response to SpeakerScott, where I confirm that the two midrange units are not in the same polarity.

a.wayne wrote:
Is there any reason why you still favor using gated measurements with such short reflective paths?

Other than the in-room averaged-response measurements, I use a gated measurement because I want to examine the speaker's anechoic behavior, ie, the direct sound that reaches the ear first.

a.wayne wrote:
With such a large complex speaker , why not measure it at WA?

I have only once in 30 years of measuring speakers traveled to a manufacturer to measure a speaker. One problem I encountered was that having the designer on hand interferes with the measurements because if I find a problem, the designer wants then to change something with the speaker to address the problem, which means the sample is no longer representative of what our reviewer auditioned.

John Atkinson
Editor, Stereophile

a.wayne's picture

"I have only once in 30 years of measuring speakers traveled to a manufacturer to measure a speaker. One problem I encountered was that having the designer on hand interferes with the measurements because if I find a problem, the designer wants then to change something with the speaker to address the problem, which means the sample is no longer representative of what our reviewer auditioned.

John Atkinson"

Ahhh,

Thanks for the response and explanation John ......

Regards ..

John Atkinson's picture
a.wayne wrote:
Thanks for the response and explanation John ......

You're welcome. What I find interesting about this speaker is that while the adjustments Wilson offers don't result in a time-coincident speaker, they do fine-tune the arrival times, taking the different driver polarities into account, to give a smooth blend of their time-domain outputs hence optimal integration in the crossover region. But using the phrase "Aspherical Group Delay" for this facility, no matter how effective, seems misleading.

John Atkinson
Editor, Stereophile

SNI's picture

I wonder when somebody will say thew words that really should go with a speaker like this.
The time domain is really terrable, and the impedance is even worse.
How can this ever be called high end?
To me this looks like someone without any knowledge of speaker design ran into a huge stack of components, drivers, MDF and veneer, and had a lot of fun.
If I did this speakers measured performance, I would start all over again.

The sure to come comment asking "Did you listen to it?" will be answered no, I did not, and I do not see any reason for it.
Good measurements will not promise anything when it comes to listening experiments, but bad measurements will always do so. I´ve never heard any speaker or other component perform well if the measurements were lousy.
And this set of measurements is way in the dessert.

a.wayne's picture

In the time domain , it's hard to tell based on the way John is measuring the speaker, but i fail to see what's wrong with the impedance graph.

Could you be more specific ...?

SNI's picture

The impedance from ie. 60-200Hz is around 3 Ohms or lower, this is the area with the most enrgy in music.
This lowish impedance will make the life difficult for about almost any poweramplifier, causing the output stage to operate in it´s less linear area for no reason at all.
Also class A amplifiers will quickly be forced away from their most linear mode of operation.
And of all the worst @ 60Hz you have 3 Ohms in conjunction with around 45 dgrs. of phase shift. This is horrible.
To me this looks like very bad speakerdesign, which only quality seems to be it´s size.
And we should not forget the measured time domain behavior, which looks even worse. JA has a lot of times been able to measure TD, with much better results than this. Even with speakers with just as large distance from top to buttom as this one.
So I see no excuse for the poor Time Domain measurements.

Should I say somtheng positive, then it would be, that this speaker is so expensive, that it almost certainly will be paired with very powerfull poweramplifiers, such as Krell, Boulder or some class D powerhouse maybe @ a similar pricetag.
BTW class D will probably be the only amplifier type, which can function as "almost" linear into loads like this. Class A will definately need "sauna" bias to perform at its best.

a.wayne's picture

SNI,

Thanks for the response and I do agree with your concerns , but do oppose your conclusions.

1. Firstly it's nearly impossible to design a multi driver system and maintain an 8 ohm ( where class-A ratings are valid) zmin, also 60-200 is not the bulk of most music , the difficult area for most music reproduction is in the 400- 3K Region and while 3 ohm accompanied with a -45deg phase angle could represent some difficulty to most dinky toy amps , this speaker has reasonably high sensitivity , this does go along way in alleviating drive difficulty and should not be an issue with any competent 2 ohm rated amplifier. I can imagine most listening will be done in the 1-2 watts RMS range with 200 watts or so on dynamic peaks. This would mean 2-5 watts of class-A power at 3 ohms should suffice, if this is your concern ( Only 20 watts@ 8 ohm of class-A power would be necessary to achieve this ).

2. TD, agree, but , I would have to see the anechoic/GP measurements ( with phase) on tweeter axis with the alignments done for proper TD and not setup for subjective listening as tested .

3. Actually IMO, class-D amplifiers are best suited for 8 ohm operation and not for low Z loads.

Regards ..

SNI's picture

Mr Wayne

I wish it only was flimsy power amps, that will be stressed with impedances like this speaker. But I´m afraid that will be wishfull thinking.
Even the most stable and strong amps performs better with a more human load.
But even if that is left aside, the TD is still horrible, and I´m flabbergasted that someone making speakers this expensive, can get the idea of reversing the phase of one or more drive units.

I´m sorry, but to me this looks like carpentry more than speakerbuilding, and for the latter only for one self.
As a commercial product at the asking price, we have one of these high price audio products so frowned upon by engineers.

Class D will remain linear far longer than class A will @ lower frequencies, but at higher ones class A will be able to stay linear into more difficult loads than class D.
Class A/B is not linear at anytime, but the harder the load, the more distortion you´ll get especially at low volume.

monetschemist's picture

Mr. Atkinson,

I wonder if it would be possible, and worthwhile, to do an article (maybe a series) that more fully explain what we see in your graphs? Perhaps take a couple of speakers that you have recently tested, do some more annotated graphs ("this point here shows the effect of an out of phase frammistat or perhaps a busted knobflicker"). It would be especially cool if you are able to correlate the measurement with what weirdness it creates in the listening experience...

Perhaps this is not feasible, but it seems to be an interesting idea.

John Atkinson's picture
monetschemist wrote:
I wonder if it would be possible, and worthwhile, to do an article (maybe a series) that more fully explain what we see in your graphs?

I have written 3 articles on this subject, based on a paper I presented to the Audio Engineering Society 20 years ago:

www.stereophile.com/features/99/index.html.

www.stereophile.com/features/100/index.html.

www.stereophile.com/features/103/index.html.

And in 2011 I gave an illustrated lecture on the subject at the RMAF:

www.youtube.com/watch?v=j77VKw9Kx6U.

John Atkinson
Editor, Stereophile

monetschemist's picture

I look forward to reading these! Thanks very very much.

es347's picture

..and was mildly impressed. The fit and finish on any Wilson speaker is top shelf but the sonics have never been my cup of tea..

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