Although it's more of a phobia than a fair judgment, digital signal processing has something of a bad name among audiophiles, but most subwoofer designers will roll their eyes if you proclaim the evils of DSP in their presence. DSP, arguably, has even more benefits for subwoofers than it does for other speakers. Using DSP, a subwoofer designer can deliver products with almost perfectly flat response and can push the driver and amplifier right up to their limits, but not beyond--thus achieving the maximum useful output for a given design. This kind of precision is impractical and sometimes impossible with analog circuitry. It's why PSB finally bit the bullet and created a digitally tuned subwoofer, the $1,499 SubSeries 450.
The SubSeries 450 packs a 12-inch active driver powered by a 400-watt RMS Class D (digital) amplifier, plus two 10-inch passive radiators. This is something I love to see. Often, designers use a single passive radiator that is the same diameter as the active driver. While this arrangement may look nicer and cost less, it's a compromise. A passive radiator is there to reinforce bass frequencies below the driver's resonant frequency. Because the radiator is reproducing lower frequencies, it should have more radiating area than the active driver. Combined, the SubSeries 450's dual radiators have about 39 percent more radiating area than the single active driver. Using the radiators instead of ports allows the SubSeries 450 to be relatively compact, at 16.25 by 15.75 by 16.5 inches.
The features included on the SubSeries 450 are standard fare: stereo line inputs and outputs, LFE input and output, stereo speaker-level inputs, and knobs for volume, phase, and crossover frequency (50 to 150 Hz). One nice plus here is that the stereo line outputs are high-pass filtered by 12 dB per octave below 80 Hz, which means if you send this signal to your main amplifier, the bass will be filtered out of your main speakers. And that, in turn, means setting your crossover will be easier, and your main speakers will play louder with less distortion. If you're using a stereo preamp that, like most stereo preamps, lacks a built-in subwoofer crossover, this is a huge advantage.
There's also a 3.5mm input jack for a 12-volt on/off trigger signal from an AV receiver, preamp, or home automation system, plus a USB jack that's used to power an optional wireless audio receiver.
As I do with most subs, I placed the SubSeries 450 in my room's "subwoofer sweet spot," a position where most subs tend to sound best from my usual listening position. (In my room, that's just to the left of the right-channel speaker.) I connected the subwoofer to two different systems. The first was a two-channel system using a Classé CP-800 preamp/DAC, a Classé CA-2300 stereo amp and Revel Performa3 F206 speakers, connected using Wireworld Eclipse 7 interconnect and speaker cables. The second was a home theater system using a Sony STR-ZA5000ES AV receiver and NHT Media Series speakers, including two MS Towers, two MS Satellites, and an MS Center. In both the CP-800 preamp and the STR-ZA5000ES receiver, I set the crossover point to 80 Hz.
I have to note that the SubSeries 450 includes no remote control, no special DSP modes for movies or music, and no auto room EQ--which makes its feature package rather Spartan considering the $1,499 price.
I usually start my speaker and subwoofer evaluations with music, but I was more curious about the SubSeries 450's performance with action movies. Action-movie soundtracks often push compact subwoofers such as this one past their limits. Most of these subs use passive radiators, which don't produce the chuffing commonly heard with ports but can produce banging and rattling noises that are (in my opinion) often more objectionable than port noise.
So I started by streaming The Finest Hours, a recent movie about Coast Guard sailors rescuing the crew of a stranded oil tanker during a heavy storm. I knew this movie's soundtrack would include lots of deep-bass energy, so I played the system loud and cranked up the subwoofer level an extra three dB. Despite roughly a third of the movie's soundtrack being dominated by the crashes of colossal waves, I noticed no distortion from the SubSeries 450 and no signs of distress in the passive radiators. This, I think, shows the benefits of digital signal processing; Paul S. Barton was, apparently, able to wring the maximum possible output from the driver and radiators without ever pushing them beyond their limits, something I have not seen accomplished with analog circuitry.
Of course, The Finest Hours is a new movie whose soundtrack I don't know well. Thus, I knew it was my duty to challenge the SubSeries 450 with material I knew would push its driver and amp to their limits. So I chose the "Face to Face" and "Depth Charged" chapters of the U-571 Blu-ray, which I've used to test innumerable products. "NICE!" I wrote when I heard the SubSeries 450 reproduce the sound of the titular submarine's deck cannon going off. Some subs compress on the sound of the cannon, leaving it sounding more like a "whack" than a boom, but the SubSeries gave the gun the appropriate fullness. It was just as impressive when reproducing the sounds of depth charges a few minutes later. Again, I heard a powerful, tight, precisely controlled boom rather than a whack. I knew that the SubSeries 450, like almost all powered subwoofers, has an internal limiter; however, despite the demands of U-571, I could never hear the limiter kicking in.
I could tell that the SubSeries 450 was a surprisingly good home theater sub, considering its size, but of course I wondered how it would fare with demanding music, which rarely taxes a sub's power but does reveal its fidelity. "52nd Street" from David Chesky's CD The Body Acoustic told me. This CD, like most Chesky recordings, features acoustic instruments recorded naturally with little post-processing--in this case, a double bass playing a fast line. Many subs tend to blur the sound of an acoustically recorded double bass into mud because of their inherent resonances, which often make the low notes of a double bass ring longer than they should. With the SubSeries 450, the bottom notes on the double bass sounded perfectly controlled; I could hear the natural resonance of the double bass with no added boom, delay, or lag.
"Dimples" from James Blood Ulmer's Memphis Blood CD is a different kind of double bass recording. It sounds like the bass player is using a pickup on the bass, either instead of or in addition to a microphone. The pickup enhances the lower notes of the bass, which aren't strong on their own; the result is a lot more low-frequency power. With some subs, the bass in this case starts to sound like two different instruments: the boomier, more electric-sounding low frequencies with the more acoustic-sounding overtones. With the SubSonic 450, the double bass on "Dimples" sounded completely integrated, again with no added boom, delay, or lag. "This thing really starts and stops fast," I noted.
Yet another bass style is evident on "Dirty Girl" from Jimmy Vaughn's Do You Get the Blues. This is straight walking blues, probably recorded on a four-string Fender Precision electric bass. It's not what we generally think of as a "melodic" bass line, but because it uses mostly chord tones, with relatively large harmonic intervals, the fundamental tones are all over the range between about 40 and 130 Hz. Thus, it covers the second octave of bass and most of the third. Once again, every note sounded super-clean, with no apparent resonance, no limiter jumping in, and no emphasis of any particular notes. It was just a perfect Texas blues groove. (The link here is to a live version, not the studio version I used.)
Click over to Page Two for Measurements, The Downside, Comparison & Competition, and Conclusion...