Every day it’s the same: You stand on the same subway platform, at the same time, looking at the same cluster of fellow commuters, all of you waiting to begin the long trek home. But as you feel the concrete platform begin to rumble and see the headlight play along the tunnel wall, you suddenly imagine the train careening wildly into the station and -- brakes screaming, sparks flying -- coming to a halt. Everyone else on the platform hits the deck as a blaze of gunfire erupts from the train’s shattered windows. And then the doors fly open and the arch villain strides out, ready to take you on in the final confrontation. Suddenly, the commute doesn’t seem so dull.

Once at home, still in your daydream’s grip, you pop End of Days into your DVD player and jump to the scene where the subway train, engulfed in flames, comes flying through the tunnel. But your home theater system isn’t even giving you the rumble of the real subway, let alone the slam of a train out of control. It all seems flat and distant, and you find yourself faced with the fact that your system just can’t keep pace with either the movie or reality.

It’s time to buy a subwoofer.
True, many CDs and DVDs don’t have much going on at the bottom end (below 50 Hz or so), so a sub might seem like an audiophile indulgence. But more and more discs -- especially DVDs -- exploit what lies beneath, and the big blockbuster films almost always do. So getting a first-rate subwoofer isn’t a matter of keeping up with the home theater Joneses -- it’s about experiencing all the fullness and depth movie soundtracks and music have to give.

And there are more mundane reasons for thinking about adding a sub to your speaker array. The best locations for reproducing bass aren’t the same as for higher frequencies. While you should keep your front speakers away from the front and side walls of the room, and your surrounds high on the side or back walls, subs belong on the floor -- and usually work best tucked into a corner. But a sub’s optimal position isn’t as fixed as those for your other speakers, and thanks to that flexibility, adding a subwoofer can be the single easiest way to improve your system’s overall sound.

The roundup that follows is similar to last year’s “Bargain Bassment” (May 2000), which looked at five $500 subs, but with a new wrinkle. Rather than focus on subs that sell for the same price, I gave a thorough thrashing to eight models from four manufacturers. Each company submitted a budget sub as well as a second, higher-price model so we could get a handle on what you get from a subwoofer when you move up the price scale.

Infinity gives us the biggest price spread with the $499 Interlude IL 100s and the $1,800 Intermezzo 1.2s. On the other hand, only $470 separates Polk Audio’s PSW250 ($300) and PSW650 ($770). The M&K K-9 and Velodyne VLF-810 both go for $550, while M&K’s MX-125 Mk II goes for $1,199 and Velodyne’s SPL-1200 is a cool $1,399. But more money doesn’t necessarily buy you subwoofer happiness. As we’ll see, there are a lot of other factors that go into determining which sub’s right for you -- like performance (see “In the Lab,” pages 80-81, for my measurements, including graphs of each sub’s maximum output).

     

All eight subs have line-level inputs, output-level controls, a phase switch, a variable-frequency electronic crossover, and an internal power amplifier. All but the M&K MX-125 Mk II have speaker-level inputs, some have both line- and speaker-level outputs, and all but the Polks have a crossover bypass (for use with a receiver’s bass-management facilities). All except the M&K pair and the Polk PSW250, which must be manually switched on and off, have an auto-power feature that turns them on or off depending on whether an input signal is present. The M&K MX-125 Mk II and Polk PSW650 are the only models without magnetic shielding. (See “Fast Facts” below for more on each sub’s specifications and features.) While every sub here has everything necessary to fit in with almost any home theater system, some have additional features that can help make the job easier.

Infinity
Interlude IL 100s
and Intermezzo 1.2s

You could never mistake these two Infinity subwoofers -- designed for the Interlude and Intermezzo home theater speaker systems, respectively -- for your usual black cube with a square black grille. With their graceful shapes and striking design touches, both display the kind of styling you usually associate with expensive foreign cars. The elegant curves of the Intermezzo’s platinum-finish cast-aluminum cabinet are especially striking. Even though they’re about the same size, the Intermezzo sub is nearly twice as heavy as the Interlude, with the additional weight attributable to its cabinet and 850-watt amplifier.

The Interlude and Intermezzo subs have complete feature sets and some nice extras, including 15-foot power cords that give you a lot of placement flexibility. Both have front-panel level controls in addition to the usual rearward controls. At first glance, the front-mounted control seems to be a plus -- it could be handy for making occasional level adjustments once you have the sub in place -- but setup is easier when all of the controls are in one place.

Both models also have a one-band parametric equalizer, which you can use with Infinity’s unique Room Adaptive Bass Optimization System (R.A.B.O.S.) to help find the best position for the sub and equalize its room response. The R.A.B.O.S. test and measurement kit, which includes instructions, a test CD, and a sound-level meter, comes standard with the Intermezzo; it’s a $60 option with the Interlude. You place the sub where you expect to put it, play the CD through the sub, use the sound meter to measure the frequency response at your listening position, and then plot the results on the supplied chart. The result is a nice graph of the sub’s response in your room. You then use the supplied template and response-curve “slide rule” to determine the optimum settings for the equalizer. The object, of course, is to make the bass sound as smooth as possible, neither boomy nor weak in any part of the sub’s range. (The kit, available separately, will help anyone determine exactly what kind of effect the room has on a subwoofer’s performance.)

Unlike many subs I’ve tested, both models have crossover markings that sync pretty well with the actual crossover frequencies. The Intermezzo’s line-level outputs include a 100-Hz, 6-dB-per-octave high-pass filter that’s not mentioned in the manual, and the rear control panel sports a pushbutton labeled High-Level High-Pass that’s pictured in the manual but not mentioned or specified. Guess what: it turns on a 100-Hz, 6-dB-per-octave high-pass filter for the speaker-level outputs.

In the lab, both models pumped out the kind of deep bass to qualify them as true subwoofers (rather than “bass modules” that cut off at about 40 Hz), but the Intermezzo played louder and lower. The Interlude’s 10-inch driver and 250-watt amp produced 79 dB sound-pressure level (SPL) at 20 Hz with low distortion, while the Intermezzo, with its 12-inch driver and 850-watt amp, managed 90 dB at 20 Hz and a stout 80-dB rumble way down at 16 Hz.

     

But lab measurements tell you only so much. It’s how they perform in a home theater that matters, and both proved to be true-blue subs there, too. They handled “bass-head” CD tracks -- like “976-BASS” from Bass Erotica’s Bass Ecstasy (Neurodisc) and Bass Connection’s “Pure and Perfect Bass” from Drivin’ Bass (Neurodisc) -- with aplomb, if not plaster-shattering SPL. They also did well by below-20-Hz material, like the opening organ pedal of Thus Spake Zarathustra from DVD Space Spectacular (Delos) and “Jurassic Lunch” from Telarc’s The Great Fantasy and Adventure Album.

Both of the Infinity subs also rumbled with authority when I took them for a ride with demanding DVD soundtracks like the subway scenes in The Matrix (Chapter 33) and End of Days (Chapter 17), although the Interlude had 3 to 6 dB less output at 25 Hz (as measured with my sound-level meter). On Zarathustra’s sustained organ note, the Interlude sometimes sounded slightly louder than it measured because it overemphasized the tone’s second harmonic. But it did manage to keep port noise well in check, which is no small feat.

The Intermezzo’s admirable tendency to distribute its acoustic output evenly across its bandwidth (most subs have more output at the higher frequencies) meant that it delivered more power to the bottom octaves than many other subwoofers in its class. What does that mean for you? Lots of chest-pounding bass that will envelope you when the program material calls for it and a chance to actually hear the true glory of a sustained organ pedal such as Zarathustra’s 16-Hz tone.

M&K
K-9 and MX-125 Mk II

Like Mutt and Jeff, the M&K entries are the largest and the smallest subs to attend our little party. The diminutive K-9 weighs just 22 pounds and will take up less than a cubic foot of your living space, while the MX-125 Mk II weighs 67 pounds and occupies over 4 cubic feet. (Note that my cabinet measurements include connectors, knobs, and amplifier heat sinks -- like the monster that protrudes 2 inches from the rear of the larger M&K sub.)

The MX-125 Mk II’s cabinet holds a pair of 12-inch push-pull drivers, with one behind the grille and the other mounted at the bottom of the enclosure. Push-pull driver mounting is said to reduce harmonic distortion by canceling driver nonlinearity, but the real advantage of dual drivers is that they move twice as much air.

The MX-125 has the most limited feature set in the group, with only a line-level input and no outputs of any kind. The K-9 has both line- and speaker-level inputs as well as speaker-level outputs. Both have crossover bypass switches, but there’s nothing about their crossover facilities to keep most folks from using them in a home theater system. Both also have very steep crossover slopes of around 36 dB per octave and, as with the Infinity subs, the dial markings closely matched the actual crossover response. The calibrated level-control indicators proved to be surprisingly accurate, too.

The K-9’s single 8-inch driver had remarkably good bass extension for its size, but, as you’d expect, its dual-driver big brother played a lot louder and went a lot lower -- all the way down to 20 Hz. In fact, with music or movies, I didn’t notice any difference between the two subs unless there was a lot of deep bass. I could always count on the MX-125 Mk II for a good rumble, while on a lot of the same material -- like the soul-rattling roar that opens Chapter 18 of End of Days -- the K-9 just ran out of steam. But a small sub that can go down to at least 25 Hz, if meekly, is certainly better than no sub at all. Monitoring the SPL with movies revealed that the K-9 had between 3 and 12 dB less output below 50 Hz, depending on its overall level.
At times, the K-9 had trouble keeping up with my main speakers’ 61¼2-inch woofers. As the middle and high frequencies were increasing in level, the bass stayed put, which shifted the tonal balance of the entire system upward. For instance, when I turned up the volume on Quincy Jones’s “The Places You Find Love” from Back on the Block (Warner Bros.), the percussion took on a “tonk tonk” quality. And on programs with truly Herculean bass, such as the bass-head tracks, the K-9 went into gross overload, forcing me to turn the volume way down.

The MX-125 Mk II couldn’t handle those tracks at top volume either -- nor could any of the other subs here -- but I could play them at healthy peak room levels of around 100 dB without audible noise or distortion. The MX-125 took a decent stab at the 16-Hz organ fundamental in Zarathustra. While it couldn’t do full justice to the fundamental tone, it did a fine job with the second harmonic, bested only by the Infinity Intermezzo and the Velodyne SPL-1200. It’s not every day you hear a true 32-Hz note in your listening room -- many people wouldn’t even notice that the fundamental was missing.

     

Polk Audio
PSW250 and
PSW650

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.

Velodyne
Vlf-810 and
SPL-1200

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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Bottoms Up
Take the subway long enough, and you’ll come across just about every kind of person there is. Write about subwoofers long enough, and you’ll experience every kind of bass performance at just about every price. So how did these pairs of subs from Infinity, M&K, Polk, and Velodyne fare?

Two of the four subs in the lower price tier -- the Polk PSW250 and the M&K K-9 -- have such limited output at the lowest frequencies that they’re arguably not subwoofers at all. But both are excellent woofers with distinct advantages: the Polk costs only $300, and the $550 K-9 is about the size of a bread box. If you’re short on either cash or space, and don’t demand the loudest and deepest bass, one or the other could be right for your home theater.

On the other hand, the two remaining entry-level subs -- Velodyne’s $549 VLF-810 and Infinity’s $499 Interlude IL 100s -- do qualify as true subwoofers because they can play down to 20 Hz with low distortion, albeit at lower SPL levels when compared with their big brothers. But even here, the Interlude managed to hit a very respectable 79 dB SPL -- and it’s one of the best looking subs in the lot.

Stepping up to the subwoofers in our higher price tier gets you bass that is louder and, in some cases, lower. All four models -- the Polk PSW650 ($770), Velodyne’s SPL-1200 ($1,399), the Infinity Intermezzo 1.2s ($1,800), and M&K’s MX-125 Mk II ($1,199) -- hit average SPLs in the 25- to 62-Hz range that exceeded 105 dB, which means they’re capable of producing bass that’s as loud as what you get at your local movie theater! And if you’re looking for a relative bargain, Polk’s PSW650 costs $430 less than the next sub in the bunch. (That its amplifier is rated at only 165 watts, while the Intermezzo 1.2s and SPL-1200 are rated at 750 and 850 watts, respectively, only shows that amp specs often have little to do with subwoofer performance.)

If the very deepest, subterranean bass is what you crave, then you’ll have to turn to the most expensive subwoofers in this group -- the Infinity Intermezzo 1.2s and the Velodyne SPL-1200. Both can reach all the way down to a bone-rattling 16 Hz, performance that will have you running for cover the next time you pop End of Days or The Matrix into your DVD player. And while the Velodyne was able to play slightly louder than the Infinity in the critical range where you’ll find most bass, at 16 Hz the Infinity was able to outrumble the Velodyne by a healthy 7 dB. Now that’s a subwoofer!

Fast Facts In The Lab