NHT Xd active loudspeaker system Page 2

This was resolved in two ways. First, I measured an in-room response that dipped several dB in the upper-bass range centered on 130Hz. This detracted from the general impression of weight, warmth, and richness of sound. While the crossover slope between the XdS and XdW may be a very steep 48dB/octave at 110Hz, there is still significant signal overlap between the woofer and satellites; the positioning of the woofer is important. A lower frequency, of course, would compromise the power-handling limits of the XdS's 5.25" driver. I found that moving the XdW forward so that it was the same distance from the listener as the satellites filled in the integrated response, as confirmed by instrument and ear.

But I was the real culprit: I was simply too timid with the volume control. Perhaps my long-term bias toward big speakers was making me treat this little system with condescension, but when I stopped babying the Xd, almost all of my reservations about its performance went out the window.

Let's start with the basics: the human voice. The two-way XdS, acting nearly as a point source and with virtually the entire range of the human voice within its compass, reproduced voices naturally, without added bloom or coloration. Well-recorded, closely miked singing, such as Lorraine Hunt Lieberson's on her Handel Arias (SACD/CD, Avie AV0030), or the soloists on La Tarantella (SACD, Alpha ALPHASACD503), stood out in relief, their accompaniments defining the space behind them. Larger vocal forces, from Polyphony to the Mormon Tabernacle Choir, were rendered as ensembles of individuals, maintaining resolution and image granularity regardless of the dynamic scale.

Instruments, from individual soloists to large orchestras, were just as well defined in tonality and space through the Xd. I was particularly taken with Julia Fischer's new set of J.S. Bach's Sonatas and Partitas for Unaccompanied Violin (2 SACDs, Pentatone PTC 5186 072), recorded with less ambience than is usual for Pentatone—I felt as if I were no more than 5' from her violin. The clarity of the illusion of the central image was so good that even its vertical dimension was convincing.

And it was the Xd system that first allowed me to appreciate the new Water Lily Acoustic SACDs of Yuri Temirkanov's performance of Mahler's Symphony 5 (WLA-WS-76-SACD) and Alexander Dmitriev's of Shostakovich's Symphony 7 (WLA-WS-77-SACD), both with the St. Petersburg Philharmonic. The two-channel sound, somewhat congealed through my big-city system, was clarified enough by the Xd that I could discern the unique perspective and the individual instrumental choirs, even though producer-engineer Kavi Alexander's classic Blumlein miking technique means there's no instrumental highlighting. (See Art Dudley's "Listening" column in the October issue for more about these releases and their creation.) These recordings also revealed the Xd's sheer potency: Normal credulity made it hard to believe that such large-scale events, spread wide and deep, were coming from such small speakers. This is doubtless a result of good matching of the amplifiers to the demands of the speakers.

Not only was the Xd system capable of big, spacious, wide-range sound, it was nearly immune to conventional room problems. You know the principle: Absorb or diffuse the first reflections from the sidewalls so that those early reflections don't screw up the imaging. This is partly because most speakers' off-axis responses only vaguely resemble their on-axis responses and both contribute to the perceived balance. The Xd's accurately customized, extremely steep crossovers are supposed to linearize the XdS's on- and off-axis responses, at least in the horizontal plane. I found that I could remove my freestanding Echo Buster wall treatments and still get a great soundstage from the Xd system without corrupting the imaging specificity.

But the beauty of NHT's approach went beyond freeing me from concerns about wall treatments. The Xd is also less critical of other domestic issues because its DSP options can compensate for boundary proximity. Of the XdA's four settings, I was able to test only two. The default setting is for a freestanding location several feet from any floor, wall, or ceiling, and this was how I enjoyed the Xd most. I also tried the Xd with all three speakers flat against my room's front wall. At normal listening levels, the appropriate EQ compensation reduced the system's tendency, due to its nearness to the wall, to "shout." These problems could return at really high levels, but this was of little consequence—those levels were incompatible with serious listening or even sanity. I couldn't try the EQ setting for corner placement because my room's only unoccupied corner is behind a door. The last EQ setting is for a single XdS placed on a large object, such as a TV. Again, I could not assess that, but I remember that a highlight for me of the 2005 Consumer Electronics Show was a brief demo of a 6.2-channel Xd system—and if I recall correctly, the center XdS speaker was inside an entertainment center.

Given a well-recorded ensemble of the size that might rationally fit into my listening room, the Xd system virtually disappeared. This uncanny effect was accomplished by its balanced and open sound, as well as by its complementary room interactions and appearance. On the Chris Lomheim Trio's The Bridge (SACD, Artegra ART2004), the piano, bass, and drums were immediate, tight, and focused, with no noticeable confusion from the sidewalls or, indeed, any awareness of the listening room itself—just the music. Because the Xd speakers are so small and so visually unobtrusive, they encouraged the illusion of transport; other speakers demand that I close my eyes to achieve the same level of enjoyment.

Comparisons
While the XdS satellites are a bit smaller than my warmer-sounding Paradigm Studio/20s, the Xd system easily outperformed them in dynamics and bass. The Xd was also more smoothly integrated across the audible spectrum than either the Studio/20s or the Paradigm Studio/60s. As nicely as the Paradigms work in my room, there are moments when I can hear that each has more than one driver. With the XdSes and XdW the same distance from my listening seat, I never heard anything other than a unified sound source; in that regard, the Xd system approached the performance of the B&W 802Ds that I will be reviewing next month. The presentation, however, did seem more light-weight than the big B&W at low levels, much like small planar speakers such as my old Stax ELS-F81s or Magnepan's MGMC1. This may simply be due to the Xd's radiation patterns not exciting all room modes, or a lack of coupling to them at low levels. Whichever, this reduced interaction with the room contributed to my observation that the Xd system seemed less limited by the room when pushed to very high dynamic levels.

The Xd's bass was nearly as full and extended as that from a pair of Paradigm Studio/60s, but couldn't compete with the output of the B&W 802Ds or the Revel Ultima Studios. Nonetheless, the quality of the XdW's bass was competitive with any of them. When I piped the stereo signal through the Outlaw ICBM bass-management system, all frequencies below 40Hz were sent to my Paradigm Servo-15 subwoofer, which added a wallop to the bottom end that the Xd, as configured here, couldn't duplicate. Of course, the XdA provides drive for a second XdW, in stereo or dual-mono, and that might be a better solution if you're as much of a bass addict as I am. But the unassisted Xd did measure nicely to below 25Hz in my room; normal folks need not apply for these extras.

The other area of distinction was the midrange, where the Xd's presentation of voices never seemed lacking but rarely gave me the shiver of eerie recognition that I get from the B&Ws or the Revels.

On balance, the Xd could go toe to toe with any of these speakers. Given its design and physical configuration, it's likely to outperform them in real domestic listening rooms without acoustic treatment or major spousal accommodations.

Conclusions
NHT's Xd is a remarkable system whose small size and flexibility in placement should make it welcome in most homes. Its small drivers do place a limit on ultimate volume levels, and adding more speakers on the same channels might compromise the Xd's marvelous in-room behavior and imaging. That limit, however, is well beyond what even most audiophiles might need. Add in its clarity and a neutral harmonic balance unfettered by output level, and you have a truly outstanding system that works in the average home.

However, the Xd is more than just a speaker. All of its electronics contribute to the result, particularly the digital equalization and crossover, which make a felicitous marriage between amplifiers and speakers that the average audiophile can only dream of accomplishing by the usual mixing and matching of components. Moreover, NHT has designed the Xd as a modular, expandable system that can be configured as necessary for two-channel and multichannel applications.

The NHT Xd is the best thing to come down the pike in a long time. I hope it is a harbinger of designs to come. The current Xd system, however, is completely satisfying in itself—its presence in my listening room is an enhancement both visual and aural. Because the Xd's performance is competitive at the highest levels, anyone interested in high-quality music reproduction must hear it. It might convince you to reconsider a lot of your accumulated equipment, but beware—if you bring along your nonaudiophile spouse, you may have a lot of explaining to do, about why your current system is both more complicated and less attractive-looking.

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NHT
6400 Goodyear Road
Benicia, CA 94510
(800) 648-9993
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