What's the first word that comes to mind when you think of subwoofers, ignoring a no-brainer like "bass"? Impact, perhaps? Weight? Punch? All are reasonable descriptors in the Platonic sense, but the word that comes to my mind is "compromise." By that I mean, when choosing a new subwoofer, you're likely balancing four distinct variables: unobtrusiveness, affordability, depth, and articulate musicality. Crank up the dial on one of those variables, and the others likely plummet, with rare exceptions.

Meet one of those exceptions. RSL's Speedwoofer 10S may seem at a casual glance to be a merely tweaked version of the company's older Speedwoofer 10 (which Brent Butterworth covered in his review of the CG4 5.1 a couple of years back), but in fact this new model is the result of several years of research and development on RSL's part, the goal of which was to design a new sub that delivered something that other offerings in its price range don't--namely, significant, distortion-free output below 30 Hz, combined with articulate, musical bass from the bottom of its output range to the top. The ultimate goal, according to Joe Rodgers (son of Rogersound Labs founder Howard Rodgers) was to "significantly push the performance boundaries among top subs in the $500 to $700 range."

A laudable goal, indeed. But consider this: the RSL Speedwoofer 10S doesn't sell for $500 to $700, or even $750 as its predecessor does. It retails for a mere $399, or $449 if you opt for the wireless transmitter.

Even at that ridiculous price, the Speedwoofer 10S sports the sort of distinct features that make RSL speakers what they are, including the company's proprietary Compression Guide technology that redirects internal sound waves in interesting ways to minimize internal resonances. After a bit of controlled compression and expansion, those waves vent out of a long, thin, rectangular port just beneath the sub's high-excursion, cast-frame 10-inch driver. If you're at all familiar with RSL, there's no surprise there.

What may come as a surprise is the Speedwoofer 10S's 350-watt Class D amp, which is a bit of a departure from the 375 watts' worth of Class AB amplification provided for the Speedwoofer 10. Also somewhat surprising, considering its price, is the fact that the 10S doesn't skimp on connectivity. In addition to its built-in wireless receiver, it also features stereo line-level inputs and outputs, speaker-level ins and outs (which are getting rarer at any price point), a variable phase control knob (0 to 180 degrees) instead of the more common phase switch, a variable crossover knob (40 to 200 Hz), a crossover bypass switch, and of course a volume control.

The other noteworthy thing about the Speedwoofer 10S, at least in terms of surface considerations, is that its cabinet isn't quite as large as you might expect for a 10-inch ported sub. At just 16 x 15 x 16.75 inches, it's notably smaller than many offerings in its driver-size/performance class, making it easier to place and easier to ignore in terms of aesthetics. Don't let its size fool you, though; with rated low-frequency extension down to 24 Hz and plenty of useable acoustical energy down to 20 Hz, this little beast is a lot harder to ignore once you turn it on and crank it up.

The Hookup
Since I run multiple subs in all of my reference audio systems here at home, RSL was kind enough to send me a pair of Speedwoofer 10S subs for review, both of which I tested in multiple configurations.

I started in my stereo listening room, relying on the subs' speaker-level connections and internal crossover to mate them with a pair of MarkAudio-SOTA Viotti One loudspeakers, driven by a Classé Sigma 2200i integrated amplifier. I then moved them into my bedroom home theater system, in which they were matched with a quartet of RSL's CG3 bookshelf speakers and CG23 center channel (a separate review of which is coming soon), all driven by an Anthem MRX 1120 receiver, with the subs' crossover bypass switch engaged and all bass management (and room correction) handled by the receiver itself.

In neither case did I run into any setup issues, aside from the fact that dialing in the correct crossover point between the subs and the Viotti Ones proved to be a bit of a guessing game, due to somewhat imprecise labeling on the Speedwoofer 10S's crossover control. That's merely an observation, though, and hardly a complaint.

The one surprise that I did run into when setting up the subs in my home theater system is that they boasted a bit more output than I would have expected given the size of their cabinets. I started with their volume knobs right at 12 o'clock (50 percent volume) and found that Anthem Room Correction simply refused to proceed until I dialed their combined output back a good bit. Setting both subs' volume knobs to left at 10 o'clock (with almost imperceptible differences between them to account for the fact that I needed to turn the left sub up about 0.5 dB to balance their output) did the trick. It's a pretty decent-sized room, measuring right at 13 x 15 x 8 feet, so the fact that the subs filled it with plenty of headroom left to spare was heartening, indeed.

Performance
I began my test, as I mentioned above, with a few days of two-channel music listening, starting with a track that I normally reserve for testing room correction systems or subwoofer EQ systems. In this case, though, I was running the system with nary an ounce of EQ.

The track in question is "Hyperballad" from Björk's second post-Sugarcubes release, Post (Elektra). The reason I use this track to test room correction or sub EQ is that its bass line is a seamless blend of sustained sine waves ranging from about 41 Hz to 71 Hz, with no breaks between them. As such, it's perfect for sniffing out uneven bass performance. If one note sounds particularly louder than the others, it's a pretty clear sign that something is amiss.

Even without the benefit of EQ, the RSL subs cranked out the low end of the song cleanly, evenly, and powerfully, with no noticeable spikes or dips in output. I heard no audible distortion or chuffing, but plenty of slam-you-in-the-gullet weight.

Satisfied that the Speedwoofer 10S could handle the deepest depths of pretty much anything in my musical collection, I set my sights (well, my ears) on the upper end of its output range with the track "Roses" from OutKast's Speakerboxxx/The Love Below (Arista), which features a pretty hard-hitting bass line with plenty of energy between roughly 60 Hz and just about 100 Hz. In other words, its bottom end tiptoes all over the crossover point between the subs and sats, making it a great track to test the upper end of a sub's output. Here, too, the Speedwoofer 10S lacks for nothing, delivering not only the visceral slam of that undulating bass line but also the nuance that's sometimes lost with larger subs. Mind you, I'm under no delusion that this is an audiophile recording, but it's hard not to be impressed by the way the RSL sub doesn't muddy the song's rhythm section the way other (even much more expensive) subs do. There's an intricacy to the bass line--quick little runs here and there (especially in the chorus)--that often gets lost in the mix. But not here. Here, the combination of strength and nuance is hard not to appreciate.

Moving to movies (and, in case it doesn't go without saying, from the stereo system to the full surround sound setup), I popped in one of my favorite subwoofer-stressing Blu-rays--Scott Pilgrim vs. the World (Universal)--and cued up my favorite test scenes: Scott's bass battle with Todd Ingram in chapter 13 and Sex Bob-omb's band battle against Katayanagi Twins in chapter 15. I like the former scene, in particular, because it forces the sub to handle two disparate tasks at the same time: crank out the gnarling lower notes of the dueling bass guitars that straddle the crossover point, and smother the floor with the deep, ominous grumbles that permeate the scene, especially anytime Scott is punched through a brick wall.

Here's the thing, though: I've never heard a $399 subwoofer deliver those nearly subsonic grumbles with any degree of audibility. At all. So the fact that the Speedwoofer10S does so is in itself impressive. The fact that it does so quite well, reaching deep into feel-it-not-hear-it territory with no discernible struggle, is a bit stupefying.

Click over to Page Two for more Performance notes, as well Measurements, The Downside, Comparison & Competition, and Conclusion...

Performance (Continued)
The latter scene, the battle of the bands, is more a test of the extremes in between those. Here, the goal is to punch. Hard. And punch hard the Speedwoofer 10S does. In fact, in the second half of the battle (after Scott and his band pick themselves up and brush themselves off for another go), the subs kicked up enough of a breeze to flap the legs of my Chewbacca jammies, even from seven feet away ... yet I never heard the slightest hint of port noise.

Again, though, what impresses me most isn't that the Speedwoofer 10S is capable of cranking out such bass. It's more the fact that it does so with a nimbleness and richness that's surprising. Looking at my testing notes I see the question, "What's the opposite of 'one-note'?" Whatever it is, that's the adjective I'm clawing for here. What RSL's engineers have cooked up here is a delicious blend of fury and finesse.

Measurements
Here are the measurements for the RSL Speedwoofer 10S, provided by Brent Butterworth. (Click on the chart to view it in a larger window.)

Frequency response
±3.0 dB from 29 to 145 Hz

The chart shows the frequency response of the Speedwoofer 10S. It's admirably flat using the LFE input (blue trace), and it extends high enough that the sub won't present any problems if you're crossing it over to the main speakers using the crossover built into your AV receiver or surround processor.

I measured the effects of the sub's low-pass filter (crossover) circuitry by setting the knob to 100 Hz, which was the only marked setting other than 40 or 200 Hz. As I've seen with many subs, this control is not accurately calibrated; the -3dB point at the 100 Hz setting is 71 Hz; at 100 Hz, the response is -10.5 dB. So, if you use the sub's internal low-pass filter, start by setting the frequency 20 or 30 Hz higher than you think you need to. It's no big deal, though, because if you're using an AV receiver you're bypassing this filter--and if you are using this filter, you should set the filter frequency and the sub level by ear, anyway.

The CEA-2010 output measurements are excellent for a subwoofer of this size and price. They're almost the same as I measured from the SVS $699 SB-2000, which has a 12-inch driver and a 500-watt amp; the SB-2000 averages +0.6 dB more output between 40 and 63 Hz and -0.1 dB less output between 20 and 31.5 Hz. Both of those results are within CEA-2010's margin of error. Note that the max output of the subwoofer at all frequencies above 20 Hz is determined by its limiter, not by the distortion rising above the CEA-2010 thresholds--although at 31.5 Hz and 25 Hz, the distortion at max output is running pretty close to the thresholds. So basically, this limiter is tuned in what I consider to be the optimum way.

Here's how I did the measurements. I measured frequency response using an Audiomatica Clio FW 10 audio analyzer with the MIC-01 measurement microphone. I used ground plane technique, with the microphone on the ground two meters from the front of the subwoofer, and smoothed the result to 1/12th octave.

I did CEA-2010A measurements using an Earthworks M30 microphone and M-Audio Mobile Pre USB interface with the CEA-2010 measurement software running on the Wavemetric Igor Pro scientific software package. I took these measurements at two meters peak output. The two sets of measurements I have presented here--CEA-2010A and traditional method--are functionally identical, but the traditional measurement employed by most audio websites and many manufacturers reports results at two-meter RMS equivalent, which is -9 dB lower than CEA-2010A. An L next to the result indicates that the output was dictated by the subwoofer's internal circuitry (i.e., limiter), and not by exceeding the CEA-2010A distortion thresholds. Averages are calculated in pascals. (See this article for more information about CEA-2010.)

The Downside
You'll note that, in all of the above testing, I relied on dual subwoofers, which is the norm in all of my sound systems throughout the house. I did, of course, test the Speedwoofer 10S in isolation. And although it remained impressive, I did notice that its output was a little more uneven. Of course, that statement is axiomatic: two subs will always give you more even performance than one. In the case of the Speedwoofer 10S, though, I found that the solo sub performance was, in either position, slightly more wobbly at the upper end that other subs I've tested in its class. (And by "in its class," I really mean subs that sell for $100 to $300 more.)

That put a little extra work on the plate of the Anthem Room Correction, which wasn't quite able to fully fill in a few of the valleys between 80 and 100 Hz. But it certainly got close enough to create a good blend between the sub and sats.

Other than that, it's really hard to find fault with any aspect of the Speedwoofer 10S (and even the above observation could barely count as a "fault"), especially given its price.

Comparison and Competition
In the world of affordable, high-performance, Internet-direct subwoofers, two obvious competitors to the Speedwoofer 10S come to mind. The first, and perhaps most obvious, is the SVS PB-1000, a ported 10-inch sub with similar connectivity and similar power. The PB-1000 does boast lower rated bass extension (down to 19 Hz, but it is a good bit larger (nearly three inches taller and deeper) and sells for $100 more.

Hsu Research's VTF-1 MK3 subwoofer is another obvious competitor. It's a perfect price match for the Speedwoofer 10S, but it stands apart in a couple of distinct ways. First, it features a dual ported design, one or both of which can be sealed to tune the sub's performance. It also features a variable Q control, making it an impressively tweakable subwoofer, especially at this price point. Again, though, it is a good deal taller and deeper than the RSL.

Conclusion
In looking over what I've written so far, I'm a little disturbed by how frequently I've made reference to price. In doing so, I don't want to give the impression that the RSL Speedwoofer 10S is merely a great value. I'm not merely wagging my tail because of what it delivers in relation to other subs with a similar sticker price. By any measure, this is a fantastic 10-inch sub, one that in many ways delivers the performance of a 12-inch offering. If it sold for twice the price, I wouldn't hesitate for a moment to recommend it.

In a way, I actually am recommending that you spend twice the price--because the Speedwoofer 10S, when paired with itself, delivers the sort of clean depth and nimble upper-low-bass performance that I never would have dreamt possible from subs of this size (much less this price!) when I constructed my first home theater system back in the mid-90s. Throw in free shipping and a 30-day free trial, and this one is positively a no-brainer.

Additional Resources
• Check out our Subwoofers category page to read similar reviews.
• Rogersound Labs CG4 5.1 Speaker System Reviewed at HomeTheaterReview.com.
• Visit the RSL website for more product information.