REL Studio III subwoofer:
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Then Hager began jamming the sub into the corner and slowly pulling it out on the diagonal, equidistant from the side and front walls. At a point about 6" from room corner to enclosure corner, the drum beat from "Cosmos, Old Friend," from the Sneakers soundtrack, sounded more solid, heavy, and loud than it had before. That was where the subwoofer was left.

Hager switched the low-pass filter to the bottom of its range, 22Hz, then slowly advanced the Studio III's gain control until the bass-drum beat was solid and clear. Advancing it further made the drum sound more diffuse, with an image unrealistically large. Setting the gain lower restored the image to a more natural size. Next, the optimal crossover filter point was identified by advancing the Coarse control through its four steps. Again, the drum sounded muffled, swollen, and distorted when the Coarse control was advanced from "A" to any of the higher settings. The same procedure was then used for the Fine control. To my ears, this logical process of elimination identified 27Hz as the optimal low-pass filter setting for the Studio III in my room.

Measuring
To determine the frequency response of the expert Sumiko setup, I placed the Velodyne DD-18's room-calibration microphone on the back of my listening chair at my seated ear height of 37". I then used the Velodyne DD-18's signal generator, microphone, and onscreen spectrum analyzer to measure the response of the combination of Quad ESL-989s and REL Studio III at my listening position. (To measure the room response, I shut off the Velodyne DD-18's own woofer by setting its volume to "0." I ran an interconnect from the DD-18's Video Out jack to the Video In jack of the 13" TV set I used to display the DD-18's System Response screen. The DD-18's internal signal generator delivered a line-level sweep of the 20-200Hz range every three seconds, this fed to my preamplifier for driving my overall audio system.)

Without the sub (fig.1), the frequency response of the Quads showed a dip at 60Hz and a peak at 40Hz, with rapidly declining response below 40Hz. When the Studio III was switched in (fig.2), the frequency response was extended down to 20Hz, with a peak at 40Hz and another one at 25Hz. The response below 40Hz was elevated several dB above the response above 40Hz, probably as a compensation for the natural rolloff in sensitivity of the human ear in that range when the REL was tuned by ear.

Fig.1 Quad ESL-989, no subwoofer, in-room response (25dB vertical range).

Fig.2 Quad ESL-989 with REL Studio III, in-room response (25dB vertical range).

Listening
The REL Studio III had no difficulty covering the standard subwoofer spectrum of 25-40Hz. During my listening sessions, I was more aware of the bass than I'd expected to be—bass that had a softer, airier quality than I've heard from some other subwoofers. This may have been the result of the lack of a high-pass filter. Yet it also had all the acoustic muscle needed to produce deep, tuneful bass in my large listening room while moving lots of air. The synthesizer that provides the powerful underpinning of "Assault on Ryan's House," from the Patriot Games soundtrack (CD, RCA 66051-2), can be a torture test for most subwoofers. The REL Studio III's bass remained clean, deep, and solid, with no spurious noises to indicate that the woofer was in distress. It covered the subwoofer range without interfering with the Quad ESL-989s. There was no disparity between the speed of the Quads' midrange/upper bass and the REL's deep bass.

The Studio III delivered the punch and drive inherent in percussive bass. The concussive drum whack at the end of John Williams' Liberty Fanfare, on David Wilson's Winds of War and Peace (CD, Wilson Audiophile WCD-8823), had a snap and punch not heard from most other subwoofers. (The REL III's downward-firing drive-units probably use the wooden floor of my listening room as a soundboard. For example, the Velodyne ULD-18, which has a single downward-firing woofer, delivered the same percussive snap and floor flex on this bass-drum passage.) Michael Arnopol's introduction on double bass on "Use Me," from Patricia Barber's Companion (CD, Premonition/Blue Note 5 22963 2), had all the pace, snap, and drive anyone could want.

On the other hand, the REL Studio III did not "improve" what was on the recording. The churning electric bass, drums, and synthesizer intro of "Deeper Wells," from Emmylou Harris' Spyboy (CD, Eminent EM 25001 2), is intentionally distorted and blurred. True to the music, the REL Studio III faithfully reproduced the murky, seething muck as Harris' voice soared above, clear and unperturbed.

The Studio III's splendid pitch definition allowed me to pick out subtle shifts in bass content. "Caravan Moves Out," from Philip Glass's soundtrack for Kundun (CD, Nonesuch 79460-2), evokes the plodding, swaying, glacially slow pace of the caravan through changes in the pitches of the deep synthesizer notes, powerfully churning Tibetan horns, and double bass. The REL handled this with aplomb. In "The Carnotaur Attack," from the Dinosaur soundtrack (CD, Walt Disney 50086 06727), the Studio III reproduced the deep, thunderous, massive synthesizer notes that subtly change pitch to heighten tension and suspense. I heard the characteristic percussive pulse of Charlie Haden's standup bass in his duet with Alice Coltrane on "For Turiya," from Closeness (CD, A&M SP-710). And David Hudson's didgeridoo buzzed and throbbed powerfully in the opening minutes of "Rainforest Wonder," from Didgeridoo Spirit (CD, Indigenous Australia IA2003 D).

The REL Studio III's excellent pitch definition uncovered new information in my recordings, and revealed differences among ranks of organ pipes. There was the deep, rumbling, but solid pedal note that ends the selection from Elgar's The Dream of Gerontius on Stereophile's Test CD 2 (Stereophile STPH004); the slightly fluttering deep organ note on "Lord, Make Me an Instrument," from Rutter's Requiem (CD, Reference RR-38DD); and the mix of fluttering, airy bass notes with solid pulses from the different pedal ranks during Gnomus, from Jean Guillou's transcription for organ of Mussorgsky's Pictures at an Exhibition (CD, Dorian DOR-90117).

I heard a similar matrix of fluttering bass and solidity from organist Virgil Fox's performance of Bach's Toccata and Fugue in D Minor, on the direct-to-disc, white-vinyl recording of his The Fox Touch (LP, Crystal Clear CCS-7001). And the Studio III's low-frequency pitch definition explained why I was able to distinguish the dense, foggy, otherworldly notes of the Tibetan temple horns, synthesizer, and the deeply echoing, dreamlike chant of the Gyuto Monks in "Sand Mandala," from Glass's Kundun.

The Studio III also conveyed ambience cues, enhanced the Quads' imaging and portrayal of space, and increased the dynamic range of my entire system. The ML-2s and Quads played passages of wide dynamic range without noticeable clipping, the soundstage widened and deepened, transparency increased, and there was considerably more three-dimensionality to the sound, with clearer positioning of instruments. This effect was independent of the music's bass content. Take the hot percussion solo in "Nardis," from Patricia Barber's Café Blue (CD, Premonition/Blue Note 21810 2). Piano is on the right, double bass in the center behind the piano, snare drum at center, cymbals at extreme right; Barber's voice became more three-dimensional when the Studio III was engaged, filling out what had been a two-dimensional voice floating between the Quads.

When I closed my eyes, Mary Gauthier's voice on "Long Way to Fall," from Filth and Fire (CD, Signature Sound SIG 1273), sounded eerily like a three-dimensional person in the room with me. The soundstage widened and deepened significantly when I played Yoshihisa Taira's "Hierophonie V," from The Kroumata Percussion Ensemble (CD, BIS CD-232). Each percussion instrument—maracas, claves, woodchimes, bongos, congas, cowbells, gongs, woodblocks—could be heard unambiguously coming from a different place in the soundfield.

The deepest bass reproduced by the REL was impossible to localize. That may have been related to the Studio III's low-pass filter point of 27Hz—well below that of any other sub I've auditioned. The blips that exploded out of Morton Subotnik's Wild Bull, for synthesizer (LP, Nonesuch H-71208), and the surging, pulsing bass drum and timpani in Stravinsky's The Rite of Spring, as played by the Minnesota Orchestra under Eiji Oue (CD, Reference RR-70CD), seemed to emanate from a point midway between the Quads, not from the REL itself.

Conclusion
The REL Studio III subwoofer has the best build quality, moves more air, and has the best pitch definition of any subwoofer I've tested. And well it should have—its price of almost $9000 is twice that of the Velodyne DD-18 that I reviewed in June. In addition, the REL has all the sonic characteristics on my subwoofer wish list: the abilities to play the deepest bass notes in music and to move huge amounts of air while not interfering with the natural full-range response of the satellite speakers.

Its sub-bass reproduction is perhaps the Studio III's strongest suit. It reveals low-frequency acoustic cues that depict the venue in which the recording was made. While musically unobtrusive, the REL widened and deepened the Quad ESL-989s' soundstage. For those who own Quad ESL-989s, auditioning the Studio III is a must.

Other than its high price, did the Studio III have any limitations? Although I argue that its airier bass reproduction is how bass should sound, some may prefer more pulsatile, concussive bass. The Studio III lacks a high-pass filter, so it won't roll off the satellite speakers, which may mean a boost in the system's upper-bass response, as happened around 40Hz in my room. Finally, to get the best results it must be installed and tuned to your room by the dealer.

But the REL Studio III is one of the few subwoofers that can play the deepest bass notes and reproduce the almost subsonic ambience cues of the recording's acoustic space while remaining musical. Because of this, I highly recommend it to those who must have the very best in subwoofer performance.