Speaker Asylum: REVIEW: REL Acoustics Strata III Speakers by David Spear

Introduction

I just received a REL Strata III (in walnut) direct from REL Acoustics UK earlier this week. I haven't had much of a chance to play around with it yet, but thought I'd share some initial impressions and experiences.

By way of background, I'm using a pair of Eminent Technology LFT-VIIIA's as my main speakers. All electronics are Accuphase, and all wires are Silver Audio (balanced interconnects, biwired speaker cables). My listening room is rather small (12 W x 17 L x 10-14 H or so). The ET's are placed pretty much according the the Cardas method, and go down to about 30-35 Hz in my room. I wanted to get that last half-octave of bass, but it seemed like a no-win situation. I'd tried a powered sub (Paradigm), but didn't like what the crossover (or maybe all the long interconnects) did to the sound from the mains. There was an obvious loss in transparency, imaging, textural detail, and treble smoothness. The alternative was to go with an active electronic crossover, but I'd read that they aren't completely transparent either, and the expense of a high-quality crossover with balanced I/O's, more (long!) silver interconnects, and possibly another power amplifier seemed prohibitive.

It was a thread at this site a while ago that clued me in to REL subwoofers. (Thanks guys!) I checked out their homepage, and found their design philosophy extremely appealing. Basically, REL subs are designed to be run in parallel with the main speakers, thus eliminating the high-pass crossover and avoiding any possible degradation of the sound from the mains. In REL's words, their subs should be adjusted so they "come up beneath the main speakers".

Based on the information at REL's homepage and a conversation with Stuart at REL in the UK. I decided to take a chance and ordered a Strata III, never having had the chance to listen to (or even see) one. It took about a month for REL to build my sub, and as mentioned above, it arrived last week.

Physical/Electrical Characteristics

The Strata III is quite compact and is not too heavy for one person to carry (310 W x 416 L x 518 H, 23 kg). It is a 40-liter sealed cabinet that is constructed of 30-mm-thick MDF and contains a single 250-mm down-firing driver and a built-in DC-coupled MOSFET power amp (100 W continuous, 200 W peak). The walnut finish is absolutely gorgeous, the build quality and cabinetry are first rate, and all switches, connectors, and controls appear to be of very high quality. The Strata III is supplied with screw-in floor spikes, a thick 3-pin IEC power cord (detachable), and a 10-m 3-core signal-sensing cable for connection to the speaker posts of the power amp. The cable is quite thin and can easily be cut to the desired length. Connection at the sub end is via a Neutrik Speakon connector, which was new to me. It is a twist-on locking bayonet-type connector that looks something like a high-pressure hydraulic coupler.

As mentioned above, the sub is connected directly to the speaker binding posts that drive the main speakers. The three thin wires are simply stripped and connected the left positive, right positive, and right negative posts. The impedance of this connection is 100 kohms, so the sub does not draw any appreciable power from the main amp. The wires are only used to sense the signal output from the main amp in order to drive the dedicated amp in the subwoofer.

From the above description, it is obvious that the main speakers are run full-range. The REL has a built-in adjustable low-pass filter allowing the sub to be adjusted so that it "comes up beneath" the main speakers. Coarse and fine control knobs are provided, making it possible to set the filter in very fine steps. (Okay, I'll list them all! -- 22, 23, 25, 27, 28, 30, 32, 34, 36, 38, 41, 43, 46, 49, 53, 56, 60, 64, 69, 73, 78, 83, 89, and 95 Hz.) The control panel also has a gain control with a range of 80 dB and a phase control (0 or 180 degrees). I should mention that both the high-level (Speakon) and low-level (RCA) inputs can be used simultaneously (and are provided with independent gain and mode controls), which means that the sub can be used for both music and home theater without having to reconnect any wires or mess with any control settings.

As a final point, unlike many subwoofers, the REL does not turn itself off when no signal is received for a specified period of time. Instead, it is always active, but the circuitry is designed so that it draws only 7 watts at idle. It can therefore simply be kept on all the time. I feel that this is a great feature, since it avoids the common problem of the sub turning itself off during quiet musical passages, only to turn itself on again (usually with an annoying delay and a thump) when the music gets louder or goes lower.

Setup/Integration

Electrical connection took about 15 minutes (including cutting the sensor cord and stripping the wires), but based on my previous experience with subwoofers, I was expecting endless hassles getting the Strata III positioned optimally in the room and adjusted properly for good integration with the main speakers. However, this was not the case at all. I simply placed the sub in the corner behind the right speaker, set the filter to 27 Hz, and set the gain control to its minimum position. After that, it only took about half an hour of playing 1/3-octave warble tones and low-frequency sweeps to get everything dialed in (filter at 25 Hz, gain at about 2 o'clock, FWIW). After listening to some music, the only change I ended up making was to reduce the gain by a click or two.

Sound

I think the REL Strata III is an excellent subwoofer for the "audiophile". It has good low-end extension (20 Hz), and the bass sounds tight and (for lack of a better word) fast. The Strata III doesn't generate any unmusical sounds, such as port chuffing, panel resonances, pops, buzzes, boom, or hum. In addition, since it rolls off at a very low frequency (25 Hz), it doesn't seem to excite any of the resonance modes in my small listening room (lowest room mode:38 Hz). Integration with the main speakers is perfectly seamless, and of course, the sound from the mains is completely unaffected with the REL connected to the amp. Furthermore, given the extremely low filter setting, the subwoofer literally disappears, and it is impossible to localize its position in the room by ear. (Although it is often said that frequencies below 100 Hz or or are nondirectional, I was always able to hear my previous subwoofer as a separate sound source.) With the Strata III operating, my system sounds exactly as it did before in terms of imaging, soundstaging, transparency, and textural detail. The only change is that the music now extends down to the deep bass. In fact, it doesn't sound like there is a subwoofer in the room at all. Rather, it just sounds like my main speakers have really great bass.

Summary

The REL Strata III is a truly excellent subwoofer for the music lover. It is relatively compact, well built, intelligently designed, beautifully finished, and reasonably priced. The Strata III calls absolutely no attention to itself, and meshes seamlessly with my main speakers (which are planar-magnetics, a speaker design that is notoriously difficult to integrate with subwoofers). Most importantly, connection of the Strata III does not entail any of the compromises usually associated with subwoofers, such as the need for an electronic crossover, and the attendant possibility of degrading the sound of the main speakers.

REVIEW: REL Acoustics Strata III Speakers Review by David Spear at Audio Asylum