REL Acoustics Studio II powered subwoofer Review

From The Audio Catechism:
Q: What is a subwoofer?
A: A large, ugly device that must be placed in the most inconvenient location in the listening room—for instance, in front of the only door.
Q: What is the purpose of the subwoofer?
A: To produce prodigious amounts of low-frequency sound and to glorify its owner, who can rest safe in the knowledge that his is the biggest.

REL is such a company. Their $8000 Studio II is a no-holds-barred unit that they call a “sub-bass system.” Far from billing it as an add-on for speakers that lack bass extension, REL boldly states that any system will derive increased impact and solidity from the addition of a Studio II—even denizens of Stereophile‘s “Class A—Full Range Loudspeakers” category in “Recommended Components.”

Ah, but it doesn’t have to be that way. At the same time that home theater has made “subwoofer” a household word, many high-end companies have also discovered that a deep, tuneful bottom end can serve as the solid foundation for the cathedral of music.

The Studio II is designed to be placed against a wall, and the side of the woofer that goes against the wall is all business. Inputs and controls are arrayed across the utility panel: a phase-reversal switch; three control knobs (Coarse, Fine, and Gain); two RCA line-level inputs; two “professional-type” twist-lock connectors (High Level, which accepts speaker level, and High Level Balanced); a line-level three-pin XLR (600 ohms); a power switch; and an IEC mains receptacle. This arrangement gives the Studio II an unusually broad range of connection options and control.

The Studio II employs two heavy-duty 10″ drivers in what REL refers to as an “Acoustic Resistive Matrix” (ARM) loading scheme. The manufacturer claims that ARM offers lower distortion and improved transient performance. The driver’s back wave is loaded by a cavity that is vented “in a controlled way” (according to REL) into a smaller cavity, which then vents again into an even smaller one and, eventually, exits out the port. Even this explanation is somewhat simplified—there is yet another cavity, this one “for special control purposes.”

The Studio II is reasonably handsome (“for a subwoofer,” my wife sniffs). It’s fairly sizeable at 231/4″ by 213/4″ by 141/2″, but its black ash side panels, dark glass top, and stubby cylindrical brass legs make it look as much like furniture as a subwoofer’s going to get.

Although ARM loading is complex—not to mention difficult to construct—REL feels it offers superior performance to conventional reflex loading, since the driver is said to “see” a smaller enclosure at higher bass frequencies. REL likens this to the advantage offered by a five-speed gearbox over a three-speed.

The 300W internal amplifier is DC-coupled, using triple-paralleled MOSFET output devices. The line-level and filter stages are fully regulated to ensure isolation from the power amp. The crossover filter stages are Sallen and Key two-pole (12dB/octave) types, and the filter capacitors are 1% tolerance, nitrogen-filled polystyrene types. Quite a contrast from the cheap’n’cheerful op-amp board stuck in many subwoofers as an afterthought!

Sumiko recommends that the subwoofer be connected to the main speakers’ amplifier by way of its speaker-level inputs—this leaves your main speakers running full-range. It is fair to point out that using the REL does not therefore offer one of the main advantages of adding a subwoofer to a system: relieving the satellites of the stress of being asked to reproduce deep bass information. In addition, having three acoustic sources reproducing low bass in the room might make setup more problematic than usual. Why use this strategy, therefore?

Sumiko’s John Hunter explained: “When you derive the signal from the amplifier that drives the speakers, you tend to preserve the sonic signature of that amp—so the sound from the Studio II will better match that of the main speakers.” As I switched amplifiers in and out of the system, the sound did change, reflecting their differing characters. This was a subtle effect, certainly not day-and-night, but it went a long way toward making the system coherent. When you consider the Studio II’s staggering price tag, it will probably be used in fairly sophisticated systems—the sort where tiny nuances become more pronounced.

You can also drive the REL with a line-level signal, which I tried just to see how it worked. As you’d expect, it worked fine, but I decided to stick with the importer’s recommendations, seeing as how Sumiko has set up a lot more of these than I have. I had no complaints using the speaker-level umbilical.

But it is the bass
Setting the REL up—actually, properly setting up any topnotch subwoofer—is fairly complicated. Everybody “knows” that deep bass is nondirectional, but that doesn’t mean you can just set a woofer up anywhere in a room and get it to integrate with your primary speakers and produce deep, nonspecific bass. How come? Well, it’s the room, not the woofer, that causes all the problems. All rooms have antinodes that can cause bass to boom, and nodes or nulls that can sap the bass energy completely. This means that you must find the right place for the woofer, then you must carefully experiment with phase, gain, and the high-pass filter. This can take weeks of experimentation and listening. And the better the system, the more precisely the subwoofer must be dialed in.

Sumiko has devised a method for setting up REL woofers that is rather different from the instructions given in the owner’s manual. The manual says to stick the woofer between the primary speakers and start the tuning-in process from there. This makes for a visually balanced system, but I’ve never lived in a room where such symmetry resulted in coherent top-to-bottom response.

Sumiko finds that corner placement works in the greatest number of systems. Pressurizing the room from the corner at frequencies below 50Hz provides more linear and uniform low-frequency response, they claim. It’s possible to find good locations other than the corner, but nodal response problems tend to make this more complicated. (See Sidebar, “REL Setup Made Simple.”) Just my luck, I couldn’t use corner placement in my room, so I had to experiment extensively before settling in to a location that was adequate, if not ideal—in my room, this was along the right sidewall, about 3?’ from the kiva-style fireplace that made a corner location impossible. In extremely difficult situations, Sumiko suggests that two smaller subwoofers may work better than a single larger one.

Bass is the place
Intellectually, I realize that you can obtain deep bass from a well-designed woofer system featuring smallish drivers. However, time and again during my extended audition, I found myself saying, “All this from two 10″ drivers?” The reality of deep, deep, taut bass kept overriding my logic circuits. The Studio II really delivered the LF goods.

But man-oh-man did it take some fiddlefication to get it to do so without boominess or doubling. First off, it took two visits from Sumiko’s Stirling Trayle to find a good woofer location; then it took several weeks of minor adjustments to the Gain and Coarse and Fine bass controls to lock it in—a process that had to be repeated every time I changed speakers. Sumiko spends a lot of time training its dealers to set up its gear, so if you do buy a REL, especially one as expensive as a Studio II, you should expect your dealer to deliver, uncrate, and set it up for you—not to mention follow up after you’ve fine-tuned the system. This may not be rocket science, but it ain’t all that simple either.

My first attempt at setting up the Studio II was fun but flawed. Using EgglestonWorks Andras as the primary speakers, I put the REL along the wall behind the loudspeakers (the front wall), as close to the corner as my fireplace would let me. This also happened to be within a bass-reinforcing mode; try as I might, I never quite got a seamless blend between the Andras and the Studio II. The system boomed at about 30Hz. I did considerably extend the bass capabilities of the system and managed to rediscover just how good many of my organ-recital discs sounded. However, that boominess eventually overcame my fascination with the increased extension, and I knew it was time to have the REL take a hike to a different wall.

That made all the difference in the world. After a day spent with Stirling Trayle, as well as countless hours of obsessive-compulsive tweaking, I was amazed at what a difference the Studio II made in the system—no matter what speaker I was using. Paradoxically, I found the REL worked best with bigger, fuller-range speaker systems such as the Eggleston and the Aln Circe, rather than with smaller speakers such as the B&W John Bowers Silver Signature, ProAc Response One SC, or even really tiny ones such as the B&W DM 302 or the Polk RT5. The woofer didn’t do as good a job compensating for missing bass as it did reinforcing and extending deep bass on reasonably full-range loudspeakers.

This is not to say that it didn’t offer improvements to small monitors. Of course, it took even more fiddling to blend the Studio II’s output into the tiny ones—the higher the REL had to go, the tougher the task became. You’d expect the subwoofer to add deep bass to speakers with rolled-off LF output, and it did—the combination of the Silver Signatures and the Studio II was particularly beguiling, even though I don’t normally feel that the B&Ws sound at all anemic. What did startle me was how much more open they sounded with the subwoofer in the system—and how much better they imaged. Both of these categories rank among the Silver Siggies’ glories, so this was stop the presses!-level news.

This improvement was particularly noticeable, of course, on discs that had already impressed me with their openness and imaging. Take, for example, one of the three February 1998 “Recordings of the Month,” Sacred Steel Guitars, Vol.2—The Campbell Brothers Featuring Katie Jackson: Pass Me Not (Arhoolie CD461). It was recorded live and does a fantastic job of putting you in the middle of a very spirited celebration of faith. Adding the Studio II to the equation allowed me to hear how much presence and impact the kickdrum had—something that most stereos never get right. But the sounds were also live-er, more in the air, and I was even more conscious of the room in which the service was being celebrated.

The Romantic Organ (Epiphany EP-4) is a recital by Kent Trittle on the huge Mantler organ in the Church of St. Ignatius Loyola in New York City. If ever there was a recording designed to torture a subwoofer, this is it—73 minutes of Franck, Widor, Bruckner, Liszt, Mendelssohn, and Brahms. Some of the pedal tones literally shook the house: window frames threatened to pop out from the room pressurization, and I felt, rather than heard, the 16Hz C. Hoo-boy.

But the clarity and airiness of the oboe and trumpet stops was also tremendously increased—they seemed to float in the air just beyond the plain of the speakers. And the sense of an instrument in a huge space, the chapel itself, was far greater with the REL in the system.

Combining the Studio II with a full-range speaker such as the Andra just heightened the effect. The Andras did a superb job of re-creating the Mantler organ all by themselves, but in concert with the REL, the soundstage was bigger, more solid, and—startlingly—more delicate. More solid and more delicate simultaneously? Yes—the bottom end got solid and massive, as you’d expect, but this freed the rest of the spectrum to exist as tones lighter than air, which is, after all, what they are. As things opened up, they freed up. And that‘s something special, something I wasn’t expecting.

Baby got back
The REL Studio II has forced me to reexamine my concept of what a subwoofer does. In a world where “main speakers,” in some cases, don’t even venture below 100Hz, the term “subwoofer” has been corrupted to the point where it means “lower-midrange driver with limited bass capacity.”

This does not describe the Studio II—it truly lives up to its billing as a sub-bass system. And it seems to do so with speakers that I thought needed little or no bass reinforcement, as well as with those that benefit from an extra half (or even whole) octave of bottom-end.

But it does more than that. It also makes your primary speakers possess even more of those magical qualities you bought them for: more airiness, more sense of space, more magic.

Those qualities don’t come cheap—$8000 is as much as a Class A speaker system like the B&W Silver Signature costs. When writing a review, I always hesitate to put my wallet in the reader’s pocket; I try to describe what I heard and let the reader draw his or her own conclusions concerning value. On the one hand, the REL Studio II made a huge difference in the performance of every combination of components I added it to. On the other hand, none of the systems sounded bad without it.

But in a world where speaker cables can cost $15,000, can I really squawk about a well-designed, meticulously built product such as the Studio II—even if it is an $8000 subwoofer? It’s not a call I’d dare to make for you—you’ll need to listen to it yourself and weigh the benefits and (ouch) costs.

I’ll tell you this: If you hear the REL Studio II set up to do what it’s capable of doing, you’re going to want one bad—no matter what the cost.

Sidebar 1: Stirling Trayle on REL Setup

Since Sumiko and the REL’s manual offer different recommendations for setting up the Studio II, I asked Sumiko’s Stirling Trayle to explain his recommended setup procedure.—WP

“To begin the setup process, choose a piece of music that has a repetitive bass line that is quite low in frequency. We recommend the soundtrack to Sneakers (Columbia CK 53146) because it has a repetitive bass drum throughout, which gives you a lot of time to move the woofer around—but, more important, it was recorded in a large venue and therefore has a deep and large-scale bass signature.

“Phase Orientation: After plugging the REL in and connecting it, set the bass control’s Coarse setting to position 2 and raise the Gain control to the 12:00 position. Start your setup cut and go to the corner where the REL has been placed. Trying to ignore all other aspects of the music, listen to the bass drum and the effect the drum has on the listening room. Switch back and forth between the two phase settings (Normal and Reverse). Whichever sounds louder is correct—this means the woofer is acting in concert with the main speakers, adding bass, not canceling it.

“Room Orientation: Try orienting the woofer with the front wall (behind the main speakers) or turned 90 degrees—with the connection panel facing the side wall. The orientation that yields the most bass is, again, the correct one.

“REL Placement: Start with the REL as far into the corner as possible, then slowly move the woofer on a diagonal out from the corner, trying to keep it equidistant from the walls. Listen for the point at which the woofer exhibits increased output and the lowest bass. Somewhere between several inches and several feet from the corner, the woofer will ‘unlock’—at this point the speaker is working with the room to provide the most efficient pressurization and the lowest possible frequency response.

“Crossover settings: With the speaker properly sited and the phase set correctly, you can begin to tune the crossover. Working with both Coarse and Fine controls—and the Gain still set at 12:00—you are looking for the point at which the woofer begins to intrude on the primary speakers. Each detent on the Coarse dial is equal to four on the Fine control. (With both dials set to 1, the crossover frequency is 25Hz; with both set to 4, it’s 100Hz.) When you’ve reached the point where the woofer begins to interfere with the main speaker, you can subtly adjust both crossover setting and gain to reach a seamless integration of the two. This is the time-consuming part.

“Gain must be adjusted in conjunction with crossover changes. In general, choosing a lower crossover point necessitates more gain; selecting a higher crossover setting calls for less gain. Many audiophiles tend to set the crossover point too high and the gain too low, for fear of overwhelming the main speakers with bass—this results in a loss of bass depth and dynamics. The proper crossover point will increase overall dynamics, extend the bass frequencies, and improve soundstaging.”—Stirling Trayle

Sidebar 2: Associated Equipment

LP Playback: Linn LP12, Naim Armageddon Power Supply, Naim ARO tonearm, van den Hul Frog phono cartridge; LP12/Lingo/Cirkus/Ittok/Arkiv.
CD Playback: Audio Research CD2, Mark Levinson No.39, Meridian 508-24, Naim CD 3.5.
Phono Preamplifiers: AcousTech, Conrad-Johnson Premier Fifteen, Linn Linto, Naim Prefix.
Power Amplifiers: Accuphase M2000, Audio Research VT200, Cary CAD805C, Krell FPB 600.
Loudspeakers: B&W DM 302, B&W Silver Signature, Dynaudio Contour 3.3, EgglestonWorks Andra, Polk RT5, ProAc Response One SC, Aln Circe.
Cables: Kimber KCAG, WireWorld Gold Eclipse III interconnects; Kimber Black Pearl, WireWorld Gold Eclipse speaker cables.
Accessories: Audio Power Industries Power Wedge 112, Magro Stereo Display Stand.
Sound Treatment: ASC Tube Traps, Studio Traps, Bass Traps; RPG Abffusors; osophagistic feline.—Wes Phillips

Sidebar 2: Specifications

Description: Powered “sub-bass system” with adjustable high-pass filter, DC-coupled, 300W RMS MOSFET amplifier, and “Acoustic Resistive Matrix” (ARM) drive-unit loading. Input connections: one XLR, one speaker level, two RCA. Gain control range: 80dB. Input impedance: 100k ohms (high level), 10k ohms (XLR, RCA), 600 ohms (balanced XLR). Phase: adjustable. Drive-units: two 10″ (250mm) long-throw cast-chassis woofers. Enclosure resonant frequency: 20Hz. Enclosure volume: 72 liters. Frequency range: 14-120Hz (lowest frequency is both room- and system-dependent; upper frequency is user-adjustable). Power output: 400W peak.
Dimensions: 23.25″ (685mm) W by 21.75″ (620mm) H by 14.5″ (520mm) D. Weight: 194 lbs (88kg) net, 275 lbs (125kg) crated on pallet.
Serial number of unit reviewed: 7816.
Price: $8000. Approximate number of dealers: 48.
Manufacturer: REL Acoustics Ltd., North Road, Bridgend Industrial Estate, Bridgend, Mid-Glamorgan CF31 3TP, Wales, UK. Tel: (44) 1656-768777. Fax: (44) 1656-766093. US distributor: Sumiko, 2431 Fifth Street, Berkeley, CA 94710. Tel: (510) 843-4500. Fax: (510) 843-7120. Web: www.sumikoaudio.net.