While neither has the last word in features, both Polk subs have all the essentials. The PSW650 is missing only a crossover bypass, but it makes up for it with a separate LFE (low-frequency effects) input that does exactly the same thing by taking the low-pass-filtered signal from a surround receiver or processor. It also has a switch that boosts output by 3 dB over its full bandwidth. Both the line- and speaker-level outputs have 80-Hz high-pass filters, and you can bypass the speaker-level filter. (As with the two Infinity models, though, the PSW650's output-level control is mounted on the front panel, which can be convenient or inconvenient depending on when you need to use it.) The PSW250 lacks high-pass filtering, line-level outputs, and a crossover bypass, but most of the time you can get around that by simply setting the variable crossover to its highest setting. In other words, it's not a big deal.
As with the M&K subs, there's a marked difference in size between the two Polk models. The PSW650's cabinet houses a pair of 10-inch drivers, while the PSW250 has only a single 8-inch driver, so I wasn't too surprised to find a big difference in how much bass they could crank out, especially with demanding program material. During the subway scenes from The Matrix, End of Days, and The Jackal (Chapter 27), the PSW250's SPL in the 25- to 40-Hz range measured as much as 16 dB lower than the PSW650's. The 'copter whips, aftershocks, and subway rumble in The Matrix had less impact, and the film's musical score had noticeably more bass with the PSW650.
Like the M&K K-9, the PSW250 wasn't able to keep up with those killer bass-head CD tracks, but it performed surprisingly well for an entry-level sub. The PSW650 also did surprisingly well for its price on super-low material like the Zarathustra organ tone, but it was no match for the Infinity Intermezzo or Velodyne SPL-1200. A subwoofer that goes all the way down will make the first dinosaur stomp in "Jurassic Lunch" feel like a bulldozer just slammed into your house. With the PSW650, where most of the power is devoted to the upper half of the 25- to 62-Hz bandwidth, it sounded more like a low groan. To be honest, there aren't many subs in the world that can pull off this effect well, nor many that can produce an honest 85-dB SPL at 20 Hz with low distortion.
Both Velodyne subs are similar in size and weight -- the SPL-1200 is actually smaller than its half-as-expensive compadre -- and they have identical, fairly complete feature sets. The line outputs for both have fixed 80-Hz, 6-dB-per-octave high-pass filters.
Though the VLF-810 has an 8-inch driver and the SPL-1200 a 12-incher, both go deep enough to be considered true subwoofers. The VLF-810 could do 20 Hz with low distortion, while the SPL-1200 was able to hit an impressively deep 16 Hz. The SPL-1200 achieved significantly greater SPLs than the VLF-810 at lower frequencies, but the cheaper sub's passive radiator managed to maintain a graceful rolloff even with severely low frequencies. (Because it allows enclosure tuning that is impossible with a conventional port -- and is less likely to start making rude noises as it approaches overload -- a passive radiator can be very effective in a subwoofer.)
With program material like End of Days, the VLF-810 produced 6 to 12 dB less SPL below 35 Hz than the SPL-1200. Translated, this means the VLF-810 had noticeably less impact and floor-shaking power than its big brother. On the very demanding "Jurassic Lunch," though, the VLF-810 didn't begin to voice any complaints until the sound-level meter registered a bone-crunching 105 dB -- impressive for a $550 subwoofer! Both Velodynes did well with the Zarathustra organ pedal, although the SPL-1200 handled it with more authority thanks to its greater output power and more even distribution of that power.
In fact, the SPL-1200 sounded great on practically everything. When I ventured underground with The Matrix, The Jackal, and End of Days, the SPL-1200 put me in the subway, surrounding me with heavy ambient sound, shaking my floor and rocking my chair. While the "impending doom" dino stomp at the beginning of "Jurassic Lunch" came out as more of a growl than a house mover, the SPL-1200 rendered this just about as well as some "high-end" subwoofers that cost a lot more. Given its size, the SPL-1200 is one remarkable sub.
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