Subwoofer Reviews

I have a love-hate relationship with subwoofers. They tend to bring out my tweaky alter ego. Perhaps one of these sorry personae lives within you too: the perennially neurotic Mr. Hyde to your more obliging Dr. Jekyll. Hyde is the tense, never-satisfied fault-sniffer who zeroes in on sonic details that are perhaps slightly off, even when other people in the room are enjoying themselves.

With subwoofers, he's at his worst. Did you hear that?, he'll exclaim when he worries that a low bass note received too much emphasis. He nags and niggles that perhaps the integration between the main speakers and the subwoofer leaves a crater somewhere in the low-frequency band. He harps, not always believably, that he can hear where the subwoofer is, even though deep bass is supposed to be impossible to localize. Most of all, he barely lasts a song without getting twitchy about the sub's gain setting, imagining that he has to dial in exactly the right amount of deep-bass presence with each track.

This last tendency is probably the most common. I've seen it a hundred times with fellow audiophiles. Lots of rock recordings from the 1960s and '70s are bass-deficient and benefit from a modest boost below 60Hz. All good. But then we play something by Billie Eilish or Victor Wooten or Infected Mushroom, and the bass is suddenly too much—so we rush to dial it down. The setting usually stays in the ballpark when we listen to whole albums, but we'll have to remain vigilant with playlists that pull in songs from all over. Was listening to music supposed to be this much work?

But subwoofers can be wonderful, too. Many of us have experienced moments when a subwoofer made us grin with satisfaction, even excitement, and not just when we cue up movies like Apollo 13 or Mad Max: Fury Road. The long-retired Velodyne F-1200 I owned in the late '90s thrilled me every time I played certain songs. That repertoire very much included Mighty Sam McClain's "Give It Up to Love"; the opening bass note by Mike Rivard punches hard and deep and can induce giddiness with the right setup.

When I eventually bought full-range reference speakers, I tried to tell myself that my subwoofer days were over. All the same, about four years ago, I happily auditioned (for another publication) two top-of-the-line SVS models. The SB16-Ultra, with a 16" driver, and the SB4000, with a 13.5" one, were placed along opposing walls and usually played simultaneously. Two active subwoofers rather than one can smooth out bass peaks and nulls that otherwise plague almost every room. They typically also widen the sweet spot. When the evaluation period ended, the SVS beasts had to be returned, as all review products do. They'd proved very satisfying overall, so I pouted a little when the freight truck drove them out of my life.

On the other hand, they were bulky as hell, and my wife and I were glad to reclaim some of the floor space in our living room.

Deep Impact, the sequel
After I began using my dedicated listening room, in early 2023, my hankering for high-quality subwoofers returned. Pinging REL Acoustics seemed like a good idea. There are other great subwoofer manufacturers, but REL—born in Britain but especially prominent in the US—is the brand that pops up more than any other when audiophiles talk about high-end subs. Owner John Hunter readily agreed to lend Stereophile a pair of REL's No.31 Reference models ($7500 each). For my 21' × 15' space, the No.31, with a 12" carbon-fiber driver and a 900W class-D amp, seemed the ideal choice. REL's larger, louder top dog, the No.32 ($10,000), which has a 15" driver powered by a 1000W amp, might be overkill for spaces under 400 square feet or so. The models are so named, by the way, because they were designed 31 and 32 years after the company's founding.

A few months later, two of REL's "setup artists," Jerrad Perkins and Clay Parker, delivered the 115lb subs to my home in Maine. The No.31s, cosseted in their gargantuan boxes, barely fit through the door. For most of that late-July day, Clay acted as a speaker whisperer par excellence. First, he established a high-level stereo connection via two cables (one per subwoofer), which have a Neutrik Speakon connector on one end and stripped wires on the other. Clay connected the bare leads to the power amplifier's left- and right-channel speaker terminals so that the RELs would receive the same signal as the main speakers. He eventually separated my Focal Scala Utopia EVOs by at least a foot and a half more than usual, so that each tower stood roughly 2'7" from the nearest sidewall. The beefy, beautifully finished REL subs, constructed of MDF up to 2.3" thick, are a good 27" wide, with curvilinear sidewalls that taper to a back panel about 19" wide.

They ended up in spots I wouldn't have predicted. The REL crew positioned them inside my main speakers—just to the right flank of the left tower and just to the left flank of the right one. After hours of careful listening and minuscule adjustments, the No.31s stood about 14" farther away from the listening position than the Scalas, some 1.5' from the wall behind them (footnote 1).

In another surprise, the REL team settled on a handoff point of 29Hz, well below the 60–80Hz ballpark commonly advised by other subwoofer manufacturers, even when used with low-bass– capable speakers (footnote 2).

I was intrigued. Why such a low crossover frequency? And why the symmetrical placement with both subs firing forward from the front? I'd imagined that the ol' subwoofer crawl (footnote 3)—or else acoustic measurements—would dictate that at least one of the subs would go against a sidewall, or perhaps even the wall behind me.

Hunter sent me the email equivalent of a confident shrug: "We don't rely on dogma. The setup artists learn how to hear musical cues that solve room issues (footnote 4). We think of bass differently than everyone else. Proper impulse response is critical to making great music. For that to occur, bass dynamics must be in phase with the main speakers—which is why we offer only 0° and 180° options—and your subwoofers must relate to your speakers. Many others get caught up in sinewave-based analysis, which has essentially no correlation to any musical event I've ever attended. A kickdrum is pistonic; it explodes at you. You can't place that behind you and hope you won't notice such a disconnect."

By generally choosing low crossover points, REL again bucks convention—something Hunter clearly relishes. "For a subwoofer to blend properly with the main speakers, it must begin its rolloff well below the main speaker's useful output in that specific room (footnote 5). Say a speaker begins to roll off at 42Hz. Many would try to cross that over at 42Hz, but that would result in a noticeable peak right at that frequency. Our crossovers go as low as 20Hz, and while we don't often need to resort to crossing over that low, at a recent show we crossed over the left channel at 27Hz and the right one at 34." Visitors who heard the system described it as seamless, Hunter told me: "For subwoofers to not be the slow, plodding things they've mostly been for the past 40 years, we've designed them to be decidedly different."

For my listening room, Hunter says his staff chose a lower-than-expected crossover point to compensate for the gear closet on the right side of my room.

The right-channel sub sat just a little over 2' from the closet door. Hunter theorizes that this positioning could make the closet a bass trap of sorts: "The door itself acts like a tympanic membrane, but bass has the ability to also penetrate through doors and become trapped." Given the absence of anomalous-sounding bass peaks or valleys, I didn't quibble.

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Footnote 1: This meant that only their front 10" or so stood on the wool rug that covers most of my room. The remaining 18" of their depth rested on the oak floor. Clay opined this was "maybe not ideal." We considered pulling the rug a foot and a half toward the front wall, but this would've necessitated moving a heavy couch as well as lifting my equipment console. In the end, we left well enough alone.

Footnote 2: For relevant thoughts on subwoofers, see Jim Austin's As We See It in this issue.—Tech. Ed.).

Footnote 3: Read TJN's exploration of sub placement issues here.

Footnote 4: Starting in the late '80s, Hunter, then at Sumiko, developed a speaker-setup technique he calls M.A.S.T.E.R.S. that REL uses to this day. The acronym stands for Modal Acoustics Simplified Training for Electronic Retail Specialists. Hunter says that more than 2000 people in the high-end industry have taken the course, which he taught with his then-partner, Stirling Trayle.

Footnote 5: Apparently, Hunter is interested in bass extension, not bass reinforcement. Nuthin' wrong with that.—Jim Austin