Hales System Two loudspeaker Page 2
Like the Signatures, the System Two's three drivers are mounted in a D'Appolito configuration, with the tweeter in the acoustic center of the two woofers. This arrangement simulates a point-source radiation characteristic as well as reduces lobing (variations in vertical radiation patterns) for smoother dispersion and reduced sensitivity to listening height.
The crossover is second-order electrical, resulting in effective third-order slopes when combined with the drivers' acoustic rolloff. The Butterworth filters feature Wonder Cap and Solen polypropylene capacitors, Solen 14-gauge air-core inductors, and a tweeter padding network. The System Two's crossover differs from the Signature's in that the diffraction-loss compensation network is missing, and the crossover is mounted inside the loudspeaker enclosure, rather than outside as in the Signature.
There are other significant differences between the System Two and the Signature besides cabinet size and crossover. The System Two's 2" front baffle and 1½"-thick side walls are contrasted with the Signature's 4"-thick front and 2" sides. Both enclosures are made from MDF, though the less-expensive loudspeaker has a fewer number of internal braces. The System Two's cabinet design and construction are nevertheless extraordinary.
Other than these differences, the System Two is remarkably similar to its $1850-more-expensive brother. Both use Cardas internal wiring, identical crossover components, identical drivers, similar design philosophy, and both are built with a high level of workmanship.
One interesting aspect of the two Hales loudspeakers, discussed in my review of the Signatures but warranting reiteration here, is the extraordinary attention and cost devoted to making the enclosure rigid. Designer Paul Hales, a mechanical engineer by education, spent considerable design effort to minimize the enclosure's contribution to the loudspeaker's sound. In addition to starting with a 2"-thick baffle and 1½" sidewalls, the System Two's four internal braces (compared with the Signature's five) make the enclosure less prone to vibration. Further, the various panel section lengths between braces has been optimized so that one section's resonant frequency and harmonics don't coincide with another section's resonant frequency. In addition to reducing the amplitude of spurious resonances, this technique also distributes the energy evenly so that remaining resonances are surrounded by other modes rather than nulls. This renders the resonances less audible.
Removing the cabinet's contribution to the energy launched into the listening space is, I believe, a significant factor in the Signature and System Two's performance. The cabinet's audible contribution can be significant. The acoustic output of a vibrating surface is a function of that surface's area and excursion. Although a loudspeaker enclosure's excursion is tiny in relation to the drive-unit's motion, the comparatively large panel size results in its output being audible. The sonic effects of enclosure resonances include spectral colorationthe panel moves more at certain frequenciesand time smearing: the enclosure stores acoustic energy momentarily as mechanical energy before converting it back into sound. These phenomena result in annoying tonal aberrations, loss of image specificity, and smearing of transient detailall of which serve as constant reminders that one is listening to reproduced rather than live music.
The System Two replaced the Signatures in the listening room, and were located in the same place and position as their big brothers. They were 50" from the rear wall and 34" from the side walls in the 14.5' by 21' dedicated listening room. I should note that this position will produce the least excitement of room resonance modes (as calculated by Snell's computer program), and provide the least amount of room-added "warmth" to the low frequencies. Without stands the System Two's tweeter axis was 27", much lower than the Signature's 36" tweeter height. This placed my ears a full 9" above the tweeter, a condition that one would expect to produce audible consequences. Without stands, the sound lacked immediacy and was somewhat threadbare. My comments in general refer to the sound of the System Twos sitting on their dedicated stands.
After breaking in the System Two (during which they sounded overly bright and hard), I began the serious listening. It was immediately apparent that there was more than a casual similarity between the System Two and its more expensive brother. I have become intimately familiar with the Signature and was able to quickly recognize the two loudspeakers' similarities and differences.
Starting with the similarities, the System Two had an overall tonal balance nearly identical to the Signatureslean and overdamped bass, exceedingly smooth and pure midrange, and a slight tendency toward tizziness in the treble. In addition, the System Two shared another characteristic of the Signatures that wasn't immediately apparent: a very slight impression of top-end rolloff. I don't want to suggest that the System Two lacks treble energy: I'm talking about the extreme treble that doesn't seem to contain any musical information, but conveys a sense of air riding over the presentation. Some loudspeakers have an intentional rise in the top octave designed to impart a false sense of space and airiness that I find fatiguing and unnatural. Although the System Two is open and spacious, there was not the feeling of infinite treble extension heard through the Snell Type C/IV (reviewed elsewhere in this issue).