Snell XA90ps loudspeaker Page 2

The crossovers have been designed as second-order electrical and fourth-order acoustical slopes, with a "Linkwitz-Reilly or Butterworth squared philosophy," notes Smith. He juggled the midbass drivers' mass and enclosure volumes and the values of the crossover series capacitance to get a third-order corner for the 100Hz high-pass subwoofer crossover. The midbass drivers cross over at 300Hz to the upper midrange drivers, which in turn cross over to the tweeter at 3kHz. The rear tweeter has a first-order climbing response from 2kHz to 9kHz, and flattens between 9kHz and 20kHz.

The XA90ps's fit'n'finish is very good. The quality of the review samples' cherry veneer equals or surpasses finishes on previous Snell loudspeakers, including the Reference Type A system, which costs several times as much. Hardware, switches, rotary controls, and connections are sturdy and easily accessible.

Working with Smith, it took me less than an hour to set up the XA90pses and trim their many rear-panel controls. This pleasant task also included comparative far-field (16.5') and nearfield (9') listening, low-frequency signal-generator sweeps, phase checks, "sit-down, stand-up" pink-noise listening, setting all of the speakers' back-panel options, and fine-tuning their subwoofer parametric equalizers. Smith used a pcRTA 1/3-octave analyzer to set the loudspeakers' built-in parametric equalizers for flat response (25Hz-10kHz, ±2.5dB) from the nearfield ("front seat") listening position. (Snell dealers should offer this setup to XA90ps purchasers.) The right speaker's parametric controls were set to a center frequency of 34Hz and a 0.5-octave bandwidth. Smith compensated for the damping effect of my listening room's sloping, semi-cathedral ceiling on the left speaker's 20-100Hz response by setting the parametric controls to a center frequency of 65Hz and a 1.2-octave bandwidth. (Fig.1 shows the 1/3-octave in-room responses of both speakers before equalization; fig.2 after.)

Fig.1 Snell XA90ps, in-room, 1/3-octave response in LG's listening room before equalization (5dB/vertical div., red trace left, purple trace right). Note the superb pair match in the upper midrange and treble, even without equalization.

Fig.2 Snell XA90ps, in-room, 1/3-octave response in LG's listening room after equalization (5dB/vertical div., red trace left, blue trace right). Now the excellent pair match extends through the low bass.

Smith then returned to the factory to modify the crossover to improve the tweeter's response. He did this by lowering the tweeter's output by 2dB at the crossover point and gradually increasing the drop by -3dB at 20kHz. He returned to my listening room two months later to install this modification by replacing each speaker's front MTM drivers and rear internal crossover boards. Using a Phillips screwdriver, he detached the rear-panel service plate holding the speaker wire terminals, removed the original crossover pcb, and installed a new board by transferring the multiple colored leads from the one rear-panel and five front-baffle drivers to the new crossover's barrier strip. Smith pointed out that the crossover's adjustable slider resistors and air-core inductors are trimmed and adjusted by Snell technicians to match each XA90ps to a reference standard.

When he screwed the service panels back on and fired up the amplifiers, the modified XA90ps loudspeakers worked perfectly. This was convincing evidence of the speaker's serviceability—especially if the field technician is also the designer! He then rechecked the equalizer settings with the pcRTA analyzer, but no adjustments of the XA90pses' parametric equalizer controls were necessary.

For all listening sessions, the Snell XA90ps loudspeakers were placed in my preferred speaker locations: 62" from the rear wall and 45" from the side walls, on a circular area rug. Playing Stereophile's Test CD 3 for channel identification and phasing, I adjusted the speaker positions until I could hear the in-phase pink-noise signal as a tightly focused patch of pink noise equidistant between the speakers. Imaging and soundstaging were optimized when speakers and listening seat formed the apices of an isosceles triangle measuring 91.5" wide between the speakers and 108" from each speaker's tweeter centers to the sweet spot. The XA90ps' tonal balance did not change when I stood up and sat down at this seated position.

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143 Essex Street
Haverhill, MA 01832
(978) 373-6114
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