Brent has been a professional audio journalist since 1989, and has reviewed thousands of audio products over the years. He has served as editor-in-chief of Home Theater and Home Entertainment magazines, contributing technical editor for Sound & Vision magazine, senior editor of Video magazine, and reviews editor of Windows Sources magazine, and he also worked as marketing director for Dolby Laboratories. He's now on staff at Wirecutter.
The Power Sound Audio S3600i subwoofer showed me that, even after 25 years of reviewing audio products, I haven't heard everything. Nor have I lost my capacity to be surprised, delighted, and a little frightened by a subwoofer.
A glance at the spec sheet shows the S3600i ($1,749.99) is one of the most muscular subs available today. Its sealed cabinet holds two 18-inch drivers in a diametrically opposed arrangement that cancels vibration. An ICEpower Class D amp provides 1,700 watts of rated power. It's 20 percent larger by volume than the Hsu Research VTF-15H, the hulking subwoofer I use as a testing standard.
At 20 by 28 by 24 inches and 137 pounds, the S3600i is too big to plop just anywhere. It's intended for large, serious home theaters and stereo systems, not for average living rooms. Its industrial-style textured satin black finish makes it look more like a P.A. cabinet than a consumer product. Maximum output is rated at an average of 132.1 dB between 40 and 63 Hz, quite a bit higher than the 126.9 dB I got from the Hsu VTF-15H Mk2, the most powerful conventional sub I've measured to date. (I measured 135.5 dB from the Pro Sound Technology LFC-24SM; but, at 266 pounds, 60.5 inches wide, and $10,000, that's not a conventional subwoofer.)
A look at the back panel makes it obvious that the S3600i is a sonic muscle car, designed for output and bereft of the numerous adjustments and features found on many other higher-end subs. Of course, it has the usual gain (volume) and crossover controls, with the latter adjustable from 40 to 150 Hz.
However, it does have two unusual features. A delay control, adjustable from 0 to 16 milliseconds, lets you align the subwoofer acoustically with the main speakers. This takes the place of the usual phase switch or knob. Normally delay is adjusted inside the AV receiver or surround sound processor, in the "distance" settings for the different speakers, but this adjustment will come in handy for 2.1-channel systems. There's also a room size control, which can attenuate the deepest frequencies to compensate for the room gain you get using a large subwoofer in a small room.
Now it's time to find out if this sub can live up to its claims--and if it can do so without sounding like a booming car stereo, which is what I think a lot of us would expect from 18-inch drivers.
The S3600i fit into my room's "subwoofer sweet spot"--the place in my listening room where most subs sound their best--but just barely. With a sub this big, you may find your placement options more limited than usual. The only inputs are two line-level inputs, so I connected the top one of these to the subwoofer output of my Denon AVR-2809CI receiver, and later to the subwoofer output of the Classé Audio CP-800 preamp/DAC I use for stereo speaker reviews. The downside here is that there's no speaker-level connection to use for simpler stereo systems, although you can run stereo line-level signals into the inputs from your preamp.
I used an AudioControl Savoy seven-channel amp with the receiver and a Classé CA-2300 amp for the two-channel setup. For surround sound, I used Sunfire CRM-2 and CRM-2BIP speakers; for stereo, I used Revel Performa3 F206 tower speakers. In both systems, I set the crossover frequency to 80 Hz, so the subwoofer would have to handle the full bottom two octaves of bass on its own.
The delay control came in handy when I was using the Classé CP-800, which has a built-in subwoofer crossover but no speaker distance adjustment. To set the delay, I simply played a pink noise signal, placed my head roughly equidistant from the S3600i and one of the Revel speakers, and turned the delay knob until I got the fullest bass response (about the 12 o'clock position, but your optimum setting may vary).
Because my room is large (about 2,950 cubic feet) but not huge, I set the room gain setting to the three o'clock position. I also tried using it set all the way large. It wasn't a big difference; it seems my room is large enough not to have room gain problems with this sub.
The downside of this sub from an ergonomic standpoint is that it's hard to get to the controls. Reaching around the back of such a big sub isn't easy even if you have long arms. I'd prefer to have the controls moved to the front, maybe concealed behind a cover. Since appearance doesn't matter in my listening room, I simply turned the S3600i 180 degrees so the controls and jacks faced forward.
I have hosted some awesome subwoofers in my listening room over the last 13 years. I thought the best of them were all anyone could need for a room the size of mine. I was wrong.
My first experience with the S3600i was playing the Blu-ray disc of San Andreas, the earthquake movie starring Dwayne "The Rock" Johnson and Paul Giamatti. As I so often do, I got the disc running then went to refill my iced tea, so I'd skip all the annoying studio and production company trailers at the beginning. But San Andreas kicked in fast with a scene in which a girl driving a car gets caught in a rockslide; even though the system wasn't turned up super-loud, the sound made my kitchen cabinet doors rattle fiercely. That has never happened before, not even with the terrific subs I've tested in the past. When I scooted back to my listening chair, I could feel the S3600i pressurize the room and shake the house's foundation as no sub I've tested before has been able to do. Worried I might crack my drywall or rattle something off a shelf two or three rooms away, I backed off the volume. Later, when fellow AV writer Geoff Morrison stopped by and wanted to hear what this huge sub could do, I played the scene from San Andreas where Hoover Dam collapses, which sold him on the S3600i right away.
My guess is that most of the people interested in a sub with dual 18-inch drivers will focus on movies, so I'll start with my all-time-favorite subwoofer test scene, the "Face to Face" and "Depth Charged" chapters of U-571. I love this scene because it provides a few different bass tests, all of which revealed something about the S3600i's performance.
"Oh, yeah!" I exclaimed when the submarine's crew fired their deck cannon at the enemy destroyer. Many subwoofers don't have enough kick on this sound effect; they make the cannon blast sound more like someone whacking a metal trash can with a baseball bat. Through the S3600i, the deck cannon sounded more like a real naval cannon, delivering a powerful "whomp" of compression against my chest and a firm shake of my home's concrete slab. (How do I know what a real naval cannon sounds like? Because I was on the USS John Paul Jones when it fired its five-inch cannon during Friends and Family Day a few years ago.)
However, during the toughest part of this scene, when the submarine dives under the destroyer and both ships' engines rumble loudly and deeply, the S3600i actually sounded quieter than most of the big subwoofers I test. This wasn't because it lacked the oomph to play the deep notes, it's because it didn't have to strain to play the deep notes. Thus, its distortion harmonics--which are easier to hear than the fundamental tones because they're higher in frequency--were lower in level during this test than they are with the other subwoofers I've tested.
Last came the depth charges, which had more power and shake than I've ever heard before with any other system, including many custom-installed home theaters on which I've played this scene. I was amazed at how the S3600i pressurized the room, much the way I've felt when hearing ordinance exploding during simulated attacks at military air shows.
The S3600i almost seemed to sleep through the opening of Edge of Tomorrow, which starts with extremely deep, loud bass notes that have bottomed out a couple of subwoofers I've tested. And that's with the level cranked so loud that my ceiling (which is made from a dense, circa-1960 application of inch-thick sprayed plaster over drywall) creaked.
Let's admit it: Most of us would assume that a sub so large and powerful sounds sloppy and boomy with music. But the S3600i actually sounds "fast," probably because it uses pulp-cone woofers, which tend to be light in weight yet have a natural damping character that quells high-frequency distortions.
For example, on "Casa Loco" from guitarist Steve Khan's fantastic album of the same name, all the bass notes sounded perfectly smooth and even. The lowest notes swelled, filling the room without booming or excessively resonating. That's exactly the way a bass works; plug any electric bass into a good amp, pluck some high and low notes, and you'll hear what I'm talking about. The groove was right on top of the beat, with zero delay or lag; it pretty much sounded like my Revel F206s had grown a whole lot bigger. The sound reminded me of what I've heard from well-calibrated professional subwoofers in top-notch recording studio control rooms.
The S3600i produced the best pitch definition I have ever heard on the descending synth-bass line in Olive's "Falling," and I've been using this as a test track since writer Al Griffin introduced me to it in the late 1990s. Most of the big subs I've tested can play this track without distortion, but none ever played these low notes with the grace and subtlety of the S3600i.
The S3600i also sounded gratifyingly tight on well-produced, precisely played pop and rock tunes, such as Toto's "Rosanna" and Mötley Crüe's "Kickstart My Heart"--easily reproducing even the most dynamic kick drum hits without the slightest trace of lag or slowness. In fact, I was surprised that this ability to capture any groove perfectly--or, as many audiophiles would say, get the pace and rhythm right--was one of the things I liked best about the S3600i.
Click over to Page Two for Measurements, The Downside, Comparison & Competition, and Conclusion...
Here are the measurements for the PSA S3600i subwoofer. (Click on the chart to view it in a larger window.)
±3.0 dB from 18 to 239 Hz (room size large)
The chart here shows the frequency response of the S3600i with the crossover set to the maximum frequency and the room size set to large (blue trace) and small (red trace). Note that this sub has legitimate ±3dB response down to 18 Hz. Many manufacturers claim response to 16 or 18 Hz for their largest (and even some smaller) subs, but they usually don't specify how many dB the response is down at that point. You can see from this chart that setting the room-size control all the way to small reduces bass output by -8 dB at 20 Hz relative to the opposite large-room size setting. I was also happy to see that the markings on the crossover control are accurate; I set the knob for 80 Hz (counting up the marks from 40 Hz), and the filter's spec was right on.
Before I get into discussing the CEA-2010 results, I have to discuss an issue I encountered during the measurements. The numbers I got originally were lower than the manufacturer's specs, so I did another measurement session a week later, with a completely fresh setup and calibration; the results of this test were within an average of 0.37 dB and a maximum deviation of 0.6 dB compared with the first test, which is within the CEA-2010A requirement that results be repeatable to within one dB.
After sharing the numbers with Power Sound Audio, the company pointed out that the S3600i deserves special consideration because its radiating surfaces (the drivers) are at a greater distance from the measurement microphone than they would be with a front-firing subwoofer. In the case of the S3600i, the design means that the woofers are approximately 16 inches (0.4 meters) farther away from the listener, which would result in a CEA-2010 output measurement that's lower by -1.6 dB. There are various arguments one could make for and against awarding extra dB to subs of this design (and not to subs with a front-firing driver and rear-firing port, which according to CEA-2010 requirements are also measured from the side and not the front). One could argue, as the website Data-Bass did (although not without reservations), that a compensation curve could be used that incorporates the differences in room gain among subs of differing designs. For the purposes of simplicity, I've decided to go ahead and bump up the S3600i's CEA-2010 results by +1.6 dB. If you want to know the original results, just subtract that number.
Even without that extra 1.6 dB, the CEA-2010A results for the S3600i are several dB better at every frequency than with any sub I've measured to date (except the Pro Sound Technology model mentioned in the article). Even at the highest output levels at 63 and 50 Hz, total harmonic distortion is just 8.1 and 7.5 percent, respectively. At 50 Hz, I did hear a sound sort of like a rattling, apparently some sort of resonance in the driver cones. Note that I added results at 80 Hz, which are required under the new CEA-2010B standard. I also added results at 16 Hz, just because this sub can deliver that subsonic frequency without sounding like it's tearing itself apart.
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 close-miked each of the woofers, summed the result, and smoothed it to 1/12th octave. Crossover frequency was set to maximum.
I did CEA-2010A measurements using an Earthworks M30 measurement microphone, an M-Audio Mobile Pre USB interface, and 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.
A subwoofer that plays this deep and this powerfully yields most of its benefits over a "mere" 15- or 13- inch model only on movie scenes and music recordings that have extreme low-frequency content. Even on a fairly taxing scene such as the opening of Star Wars, Episode II: Attack of the Clones, in which a spaceship flies overhead, lands on a platform, then explodes, the S3600i didn't sound significantly better than the Hsu VTF-15H I usually use as a reference. It just had a little bit less distortion and a little bit more floor-shaking rumble.
I also noted that while the S3600i's pitch definition was excellent, I didn't hear quite as many of the subtleties of bassists' plucking on well-recorded, expertly played tunes such as Steely Dan's "Aja" and Holly Cole's "Train Song." Many smaller subs, such as the Sumiko S9, give me more of a sense of the "growl" of the bass and an apparently somewhat cleaner or more precise or "faster" response in the upper mid-bass region, near 80 Hz. I'm a bass player, so this matters to me; probably most listeners wouldn't notice, and I didn't notice it with, say, tunes that use keyboard bass. Since I can't set up valid blind A/B tests of big subwoofers, because two models this large would occupy significantly different acoustic environments even when placed side-by-side, I can't be 100 percent certain that my opinion isn't swayed a bit by bias here. Also, this probably isn't an issue if you have tower speakers, because you can just run those full-range or set the crossover point lower, down to about 50 or 60 Hz, so the tower speakers' smaller woofers handle most of the mid-bass frequencies.
And as I said previously, the S3600i is colossal and will be tough to find space for in many rooms, although it's not that much bigger than most of the 15-inchers I've tested.
Comparison and Competition
There are many large subwoofers that claim (and, in my experience, achieve) maximum output around 125 dB at one meter, but the S3600i hits about +6 dB above that, which is about the same result you'd get if you stacked up two of those large subwoofers. And the S3600i is actually less expensive than many of those less-muscular competitors, such as Axiom Audio's $2,580 VP800 v4, Paradigm's $5,460 Sub 1, and SVS's $1,999 PB13-Ultra.
I've encountered only a few other 18-inch subwoofers built for the consumer market. These include Velodyne's DD-18 Plus, which has Velodyne's fantastic Digital Drive auto EQ system but has only one driver and costs $5,799.
The only option I can find that's really performance- and price-competitive with the S3600i is Hsu Research's VTF-15H Mk2 DualDrive, a package of two of the company's VTF-15H Mk2 subwoofers, which costs $1,749 in satin black--the same as one S3600i, except that shipping is free on the S3600i and $286 for the DualDrive package. If you put the two Hsu subs side by side, the output would roughly match the S3600i, although the two together would be 67 larger by volume than one S3600i. You would be better off splitting the two VTF-15H Mk2s up and putting one each in of the front corners or in the centers of the side walls or front and rear walls. This would help cancel out the effects of room acoustics and would give you more even bass reproduction across a wider seating area, although you would sacrifice a few decibels of maximum output in the process because the two subs would partially cancel out each other's sound waves. The VTF-15H Mk2 is also more tunable than the S3600i because it has adjustable Q plus three loading modes (sealed, one port open, and two ports open).
Power Sound Audio has a couple of other options in a similar price range: the even larger, ported $1,999 V3600i or perhaps two of the S1500 15-inch sealed subs for $999 each. All of Power Sound Audio's products are made in the United States.
The S3600i is a special-purpose product, suitable only for large listening rooms and home theaters where performance is a priority and there's enough room for a colossal subwoofer (or, better yet, two). However, for those who have the space, it's a superb choice and an incredible value. We audio reviewers spend so much time writing about things that make subtle differences, things you have to listen pretty diligently to notice--but the improvement you get with the S3600i is not subtle. For action movies and the most demanding, bass-heavy music, it can do things you've probably never heard before...and that I bet you will really, really dig.