June 2004

PSB SubSonic 5i Powered Subwoofer
Is It A Sub Or Just A Woofer?
Review By Wayne Donnelly
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  Subwoofers have come a long way in the last 10 to 15 years, fuelled to a great extent by the rise of home theater and the apparently unquenchable desire of video movie viewers to have their timbers shivered by the booms and crashes of large-scale sound effects. There is now an extraordinary range of subwoofer choices, priced from a few hundred to thousands of dollars, and even those at the lower end of the market -- such as the $529 PSB SubSonic 5i under discussion here -- can deliver surprisingly effective bass reinforcement.

The last time this writer had serious interaction with a subwoofer was way back in 1987. Moving from a house in Orange County, California that featured a 32 by 22-foot living room with a 19-foot cathedral ceiling, to a cramped little Silicon Valley condo with a living room that felt like a wide hallway, I reluctantly had to face the fact that my behemoth transmission-line IMF Reference Standard Professional Monitors just wouldn't fit.

The initial replacements for those room-shaking Brits were Theil CS2s, whose compact footprint was better suited to the new space. The result was a distressing and depressing sense of low-frequency deprivation. The Theil loudspeakers had their virtues, but bass performance was not one of them. Hence my first subwoofer experiment.

There was no happy ending to that story. I tried for days to integrate a big self-powered sub with the Theils, tinkering with crossover frequencies, level settings and placements. Nothing could compensate for the fact that the subwoofer (a prominent brand that I have little doubt was competitive with others at the time) just plain wasn't fast enough. Sure, there was plenty of "woof" -- almost as much as my old IMFs. But the deep bass was always playing catch-up, as if the leading transients were dragging the full tones along on a leash. Back went the sub, and soon after that, back went the Theils in favor of some B & W 802s that, while certainly no big IMFs, at least had some low-end crunch.

Segue To The Present

Seventeen years, a somewhat larger and much better sounding listening room, and five pairs of loudspeakers later, the subwoofer experiment had not been repeated in my primary system. I have, however, heard enough outstanding subwoofer implementations to know that the limitations -- especially in speed -- that derailed that first effort have been largely solved. So, offered a chance to review the PSB SubSonic 5i, I was interested to see what this compact, modestly priced sub could do.

The Quick Tour

With its smallish dimensions and black vinyl skin, the 5i is an unobtrusive presence. The front features a curved snap-on grille; round ports at the bottom corners flank rotary knobs for selecting crossover frequency (50Hz to 150Hz) and volume. The rear panel has stereo RCA jacks for low-level inputs, and toggle switches for crossover in/out and phase reversal; left and right speaker cable connectors for high-level input from the amplifier; and another set for output to the left and right loudspeakers; and an IEC AC input jack for the internal amplifier.

Technical Features

The SubSonic 5i incorporates a high-efficiency, cool-running (no heat sinks required) "Class H" amplifier with a switching power supply, which the company has dubbed BASH. Such a design allows the rail voltages to swing high instantly when the program material demands it, while staying low during quiet passages. Power dissipated as heat is thereby greatly reduced, and more power is available per dollar of cost. Switching amplifiers typically have high peak power relative to continuous power. The 5i is rated for 150 watts continuous, 230 watts peak, and 450 watts dynamic peak power. This headroom enables the subwoofer to better handle the transients required by dynamic music and explosive cinema sound effects.

The heavy 10-inch polypropylene-cone woofer has a substantial video-shielded 40-ounce magnet. An oversize rubber surround allows long cone excursions for response within 3dB down to 30Hz. The 1.5-inch "throw" of the voice coil supports high continuous output without thermal compression.

PSB's anti-overload circuitry helps the SubSonic 5i remain musical while reproducing both heavy short-term peak demands and sustained high-power requirements that tend to cause audible problems with many subwoofers. The aerodynamic front-mounted ports keep port noise low, even with extremely low frequencies at high volume.

How Well Does It Woof?

A pair of these little subs spent a couple of weeks in my big system, primarily to subject them to high playback levels and accelerate their break-in. I didn't expect that they would add much, since their -3dB point (the frequency at which output amplitude is reduced by one-half -- generally considered the effective low-frequency limit of a loudspeaker) is about the same as my Eggleston loudspeakers: 30Hz. Generally speaking, my modest expectations proved pretty accurate. On most orchestral music, for example, the subs added quantity of output but did not add any significant extension. That is no reflection on the 5i, which isn't intended for use in a system of this price and ambition. The subs' contribution was welcome, however, on some juicy geezer rock from The Who, the Stones and numerous other rockers, where their mid-bass reinforcement gave the music a more visceral quality.

The real test was how the 5i would do in my upstairs secondary system, where a 40-watt Jolida 202 tube amplifier was driving loudspeakers selling from $995 (Von Schweikert VR 1) to $1,195 (Meadowlark Swift) to $1,500 (Von Schweikert LCR 15) per pair. [See our archives for my reviews of the first two of those loudspeakers.] Although my bedroom location is pretty spacious, I quickly determined that a single 5i was all I needed in that upstairs environment, where the carpeted wood floor contributes a bit of extra resonance.

All three of the loudspeakers paired with the 5i are extremely quick and lively, easily doing justice to the rhythmic vitality of a wide variety of music. And I am happy to report that the 5i proved an excellent match for their speed and rhythmic precision, in addition to providing highly desirable low frequency foundations. The VR 1s in particular benefited from the solid, tuneful contribution of the 5i. The LCR 15s, although not much larger than the VR 1s, offered a robust-sounding low end that seemed almost not to need the sub. But after a bit of fiddling with the 5i's crossover frequency control, finally settling at about 65Hz, adding the sub also made the LCR 15s' presentation more dynamic and exciting.

While I have not previously felt the need for "home theater" bass, having experienced the additional richness provided by the 5i has changed my mind to the extent that I am keeping one in the system. Switching the sub out now brings back that old feeling of bass deprivation, whether I'm watching a movie or listening to music.

To Cross Or Not To Cross

Let me note for the record that all my listening to the 5i in the reference system was with the low-level RCA inputs, driving the sub from the preamp in parallel to the main loudspeakers. Call me a snob if you like, but I really wasn't interested in squeezing the output of my 750-watt VTL monoblocks through the crossover electronics of a $500 sub.

In the smaller system, the absence of any pre-out jacks on the Jolida amplifier dictated running the amplifier output into the 5i and then out to the left and right speakers. All three loudspeaker setups were easy to optimize, and I did not feel that the fidelity of the audio signal was noticeably compromised by using the sub's internal crossover.

In Closing

Along with the proliferation of subwoofers in recent years has come a kind of "category inflation." Where once the term subwoofer denoted a driver that authoritatively reproduced the bottom octave - a capability beyond the great majority of full-range loudspeakers - it now describes specialized models whose bass output goes lower than the loudspeakers it is supporting. It is really to this latter group that the SubSonic 5i belongs. In the strictest sense it is a very good woofer. But my experience with it has convinced me that this is a worthwhile kind of product, offering cost-effective bass augmentation for smaller loudspeakers and systems.

The Canadian manufacturer PSB has long been noted for designs that provide solid performance and superb value. The SubSonic 5i is further validation of that reputation.

Specifications

Type: Self-powered subwoofer

Woofer: 10" polypropylene cone with 1.5" rubber surround

Frequency Response: 30 to 150Hz

Maximum SPL: @ 100Hz, 109dB

Amplifier Power: 150 Watts continuous "Class H"

Crossover Variable: 50Hz to 150Hz (24dB/octave Linkwitz-Riley Low pass filter)

Inputs/Outputs: Low/Line Level/LFE Gold-plated RCA Inputs and Outputs
High/Loudspeaker Level Gold-plated 5-way Binding Post Input and Output

Internal Volume: 1.01 cu ft (28.6 liter)

Design Type: Bass Reflex

Internally and Externally Video Shielded

Dimensions: 12.63 x 16.5 x 14.88 (W x H x D)

Weight: 33 lbs.

Finish: Black Ash Vinyl Veneer

Price: $499/each

Company Information

PSB Speakers International 
633 Granite Court
Pickering, Ontario
Canada L1W 3K1

Voice: (906) 331-6655
Fax: (906) 837-6367
E-mail: info@PSBspeakers.com
Website: www.psbspeakers.com