PSB Platinum T8 loudspeaker
By John Atkinson   •   November, 2003 The talented loudspeaker engineer is a man who is always in competition with himself. When PSB's Paul Barton put the finishing touches on his Stratus Gold model back in 1990 (footnote 1), I'm sure he had more ideas in mind that he could have used in a flagship design. Yet the Gold offered so much performance at such a competitive price—$2000/pair in 1991, rising to $2100/pair by 1997, then $2400/pair for the the Gold i, an evolutionary development—that it was not surprising that Barton applied his talents to developing ranges of more affordable speakers, such as the best-selling Alpha and Image series.

The Stratus Gold, which is still available, became a long-term resident of this magazine's "Recommended Components" listing. But talented loudspeaker engineers do not stand still, and neither do the resources and technology available to them. It came as no surprise, therefore, when I saw a new flagship design from Paul Barton, the $6999/pair Platinum T8, at the 2002 CEDIA Expo in Minneapolis. "Must review," I noted in my PDA, but it wasn't until spring 2003 that I received a pair of review samples. And it wasn't until I'd cleared my deck of other components in the review queue that I could focus my attention on what appeared to be a most promising design at what, in 2003 dollars, is still a competitive price, given the stratospheric prices of some other companies' flagship speakers.

The Platinum Tower
PSB's Platinum series of speakers celebrate the Canadian manufacturer's 30 years in business since its humble beginnings in 1972, when Paul Barton, then just graduated from high school, decided that designing and manufacturing loudspeakers suited him better as a career than his other passion, playing the violin. Whereas the iterations of the Stratus Gold had combined an aluminum-dome tweeter with a single 6" midrange unit and a single 10" woofer, the Platinum T8 uses two tweeters, two 4.5" midrange units, and three 8" woofers. The latter are reflex-loaded with a large rectangular port at the base of the front baffle, with both inner and outer openings flared to minimize air noise. Reflecting the modern reality for speaker companies, all of the T8's drivers are magnetically shielded for use in home-theater systems.

Starting at the top of the frequency range, one of the T8's tweeters is mounted on the front baffle, the other on the cabinet rear. The rear unit can be switched in or out of circuit with a jumper bar above the terminals, and compensates the speaker's in-room balance for the front HF unit's increasing directionality in its top octaves. (This will be more of an issue in large rooms.) The tweeters themselves are 1" units branded "PSB" but made in Norway, presumably by SEAS. They feature an aluminum dome and a neodymium magnet and are specified as offering usable response to 40kHz.

The midrange units, again sourced from a Norwegian manufacturer, use woven-fiberglass cones and rubber half-roll surrounds. They are arranged in a D'Appolito array above and below the tweeter, which optimizes the dispersion in the midrange and treble. (Strictly speaking, Joe D'Appolito's original paper included the use of odd-order crossover filters; according to its specification, the T8 uses fourth-order networks.) Each midrange unit is constructed on a low-profile diecast chassis and housed in its own sealed subchamber.

The three woofers, too, use woven-fiberglass cones and rubber half-roll surrounds, these generously dimensioned to allow the large excursions required by high-level low-frequency sounds. A 40-oz magnet structure provides the necessary muscle power, with a magnet circuit optimized for low distortion.

The cabinet is constructed from 1"-thick MDF and extensively reinforced with "window" braces. The front baffle is laminated with aluminum, which adds both stiffness and a smart high-tech look. Cast-aluminum top and bottom endcaps further stiffen and brace the enclosure. Electrical connection is via gold-plated 5-way binding posts, and the internal wiring is 14-gauge cable. Adjustable spikes and levelers are provided.

Such modern tools as Finite-Element Analysis, applied to the drive-units' moving parts, and a Scanning Laser Vibrometer, applied to drive-unit cones and cabinet panels, were used in the development of the T8. And, as with all PSB speakers, the design of the Platinum T8 was optimized using final listening tests and adjustments at Canada's National Research Council facility in Ottawa.

Sonics
My main concern in getting the PSBs set up was balancing bass weight against upper-bass bloom. With the speakers set back closer to the room boundaries, where both the Morel Octwin two-ways I reviewed in October and the big Dynaudio Confidence C4s I reviewed last March had worked well, the sound was majestic but rather overblown between 80Hz and 160Hz. I ended up with the speakers rather farther out in the room than is usual, but then I could get both a well-defined mid- and upper bass and excellent low-frequency extension. The 1/3-octave warble tones on my Editor's Choice CD (STPH016-2), for example, extended with full weight down to the 25Hz band. The 20Hz band was well down in level, but the relative absence of audible distortion harmonics meant that it was inaudible. (Very often, when people talk about their speakers having "good low bass," they are being fooled by the presence of audible harmonics. A clean 20Hz is hard to hear except at very high playback levels.)

The T8's bass definition was excellent, if not quite to the standard set by the five-times-the-price Mission Pilastro I reviewed in December 2002. Even so, the pat'n'purr of Jerome Harris' Taylor acoustic bass guitar on Rendezvous (Stereophile STPH013-2) was reproduced about as well as I have heard. The left-hand register of Anita Chang's piano on her Chopin Ballades DVD-A (Aix 0433 80014-9) had excellent weight and definition.

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Footnote 1: Reviewed by Thomas J. Norton in February 1991, with some final thoughts in April 1997. I reviewed the i development in October 1997 (click here to read all three reports).—John Atkinson