REL Acoustics designs and constructs subwoofers of serious intent. It faithfully hews to the high end’s original mission statement for subs—to reproduce music’s bottom octave, the region that extends to 20Hz or lower.  The Britannia series is a threemodel collection at the heart of REL’s line. Designed for music and home cinema, its traditional elegance and reasonable size bridge the gap between REL’s imposing statement products like the Stadium III or Stentor III and the glossy Class Dpowered cubes of the new R-Series.
In the Britannia line the B3 is the smallest. It’s a forward-firing, resistive-port design with dual downward venting chambers. Buildquality is truly first rate—30mm MDF throughout. At sixty-six pounds it has the requisite mass to prevent some enormous internal forces from physically propelling the enclosure around the listening room.
In the tradition of audio-minimalism, REL subs are equipped only with low-pass filtering. They are purpose-designed to augment main speakers that already produce a good part of the low-frequency spectrum. While high-pass filtering may improve dynamics and output for bass-shy satellite speakers, the additional circuitry can also add unwanted colorations.
REL’s preferred method of connection is the Neutrik Speakon high-level cable that refers the signal from the speaker taps of the main system amplifier to the B3. This is central to the REL philosophy that the subwoofer receives the identical signal or “voice” that the main speakers are seeing–– a method REL believes more fully integrates the entire chain of the system into the final sound.  Corner placement behind the main speakers is recommended as a baseline starting point. Detailed instructions offer genuine advice rather than boilerplate for setting phase, output, and crossover. Crossover settings are adjusted by a pair of rearpanel knobs labeled Coarse and Fine, which together permit a combination of 24 incremental adjustments over a 22–96Hz range.
The personality of the B3 combines Falstaffian weight with an authority and control that is divinely unbox-like. Instead it performs like a force of nature that effortlessly creates an octave of music where there was none. It doesn’t have the lumpy rubbery signature of the small high-power cubes or the one-note bloatedness of common ported subs. Port noise and overhang are virtually non-existent. For instance, the standup bass from “One For My Baby,” from Good Night, and Good Luck [Warner], isn’t merely reproduced with greater extension but with a richer, more dimensional character across its range. Electric bass and drums become more dynamically charged and tightly focused. Similarly during Norah Jones’ cover of “Cold, Cold Heart,” heard on Come Away With Me [Blue Note], there’s no question of the acoustic bass’ position and no gap or personality shift between sub and main speakers.
The dimensions and acoustics of the soundstage are enhanced yet the resolution of individual images is maintained. When a bass drum emerges from upstage and to the right, or a bass guitar doubles a floor drum at dead centerstage, the B3 doesn’t steer either instrument in wayward directions.
Extension and speed are only parts of the battle, however. When correctly dialed in the B3 is a team player that never imposes its character on the system—even on fast, high-res speakers like the ATC SCM 20-2 or the MBL 121. Sub/sat integration is so tight that even the unremitting whumph of Stewart Copeland’s kickdrum at the beginning of the Police’s “Murder By Numbers” on Synchronicity [A&M] never veered from dead-on centerstage—the B3 was essentially invisible and colorless. Truthfully, given its modest size, it won’t trip citywide seismographs like a Bag End system. But in my smallish listening room the B3’s output and mid-20Hz resolution is all the bass a lightly constructed Los Angeles home like mine can take.
In a perfect world you should be able to add a powered subwoofer to your system and never know it’s there. That’s largely the thrill that the high end strives for—music reproduction beyond the shadow of electronics. And this is largely the sensation I achieved with the B3. Categorically a reference-quality product— when it comes to the low frequencies there’s no question that this Britannia confidently rules the waves.
 The term “subwoofer”has been largely devalued in recent years. Catering to the LFE-driven home-theater market, any dedicated bass box with 30Hz-note pretensions is promoted to subwoofer status.
 Because of the very high (100k Ohm) input impedance the amplifier is untaxed.