Looks shouldn't even enter into it. This butt-ugly spud of a subwoofer is saved by its raison d'etre: size. No doubt inspired by the far costlier Sunfire cube, REL's tiniest model is small enough to hide out of sight. And hide it you will, because it looks as grimly functional as one of those miniature fan heaters they sell in the colour supplements. Maybe they should paint a REL logo or even a happy face on the driver surface, or rename it 'Medusa'. It's no surprise that its Spinal Tap black finish - ideal for, say, an industrial pizza oven or a jack-hammer - is actually called Grittex. But, no matter where you banish it, the Q200E will provide bass you probably never knew existed.

As it should. The wizards at REL have crammed a 250mm driver into a box measuring only 298mm per dimension, the long-throw unit filling one surface. REL calls the Q200E 'a revolutionary bass engine', and you'll pinch yourself the first time you hear what it can do. Remember: we're talking just under a cubic foot; hell, you could stick it in an LP rack.

REL has also wedged a substantial amplifier into this wee cabinet. Direct-driving the bass unit is a 200W, fully discrete, DC-coupled MOSFET amplifier featuring a balanced-bridge power supply, an 'audio grade' toroidal transformer, 25A bridge rectifier, 20,000 uF total smoothing capacitance and four 'ultra-rugged' output devices. Indeed, peak performance is stated at 400W, which makes you wonder why there's going to be an even wilder version of the Q200E boasting more power.

But aah, the drive unit. The company is staying hush-hush about this US-sourced unit although it's there for all to see; there's no grille available for this basic edition, though a grille will accompany the forthcoming deluxe model. What faces you, naked to the elements, is a fat doughnut of a surround and a flat dust-cap over the diaphragm which suggest exceptional durability. I'm guessing that it's some sort of polypropylene, but don't hold me to it. The woofer is fitted with a massive 7.6 kg magnet, contributing to the Q200E's total weight of 17kg, and it uses a four-layer, edge-wound voice-coil.

Given the magnet size, this baby is unshielded; there's no room to fit an opposing magnet. But - unlike that total yutz Matthew in EastEnders - we all know about keeping speakers away from tapes, TVs, etc., and the Q200E's size encourages distancing the unit away from sensitive items.

REL fits a dynamic electronic protection circuit called Set-Safe which maximises bass delivery and minimises distortion by employing its own brand of soft clipping. Even when accidentally hammering the REL during set-up using the Lexicon MC-1's internal test tones, the sub never sounded like it was going to break. And yet it was delivering signal loud and deep enough in torment mode which would have caused other speakers to, well, expire. Quite obviously, then, the active innards match the driver to perfection.

Because the smallest REL must serve in both audiophile systems as well as A/V surround installations, the back of the unit is filled with enough controls and sockets to ensure that the Q200E can connect to whatever form of connection is on offer. It was thus possible to try the unit in purist mode, in which case REL recommends a pair of Q200Es for true stereo performance, as well as in A/V mode driven by the subwoofer line output from a 5.1 channel surround processor, with plenty of scope for fine-tuning.

Because both high and low level inputs are provided, separate rotary controls are fitted to adjust level for either type of connection. Another rotary controls roll-off, while a fourth allows the user to select modes which invert polarity, again catering for both the high or low level inputs, or to bypass the company's Active Bass Control crossover circuitry when using the low level input. The crossover bears 1% Nitrogen filled polystyrene capacitors and is fitted to a double-sided glass-fibre board with plated-through holes. Connection to the Q200E is through gold-plated, panel-mounted phono connectors for the low level inputs, while a gas-tight Neutrik connector is used for the high level connection. Also found on the back panel are a heat sink, an lEC input socket and, just where you can't see it if you have the speaker facing into the room as you should, a green power-on LED. To that I can only say, 'Doh.'

Supplied with the Q200E are 8mm spikes and nylon feet, a 5m length of phono interconnect and a 10m cable terminated for the Neutrik connector. Proudly hand-built in Great Britain, the REL boasts a three-year worldwide warranty. Oh, and an owner's manual which is a model of clarity. So, please, read it first.

There is a philosophical problem here, which made this review a struggle: in either of my listening rooms, I have absolutely no doubt that I enjoy ample bass without sub-bass augmentation. Certain colleagues, specifically a closet headbanger named Simon who happens to handle Lexicon and Runco for the UK, insist that too much is never enough. So, whether used to augment Apogee LCRs (each with two 6in woofers) or Sonus Faber Guarneris in a room built like a bunker, the REL could only enhance to a slight degree. Instead, I had to turn to speakers in obvious need: LS3/5As, Genexxa LX Pro 5s, Tannoy R1s and the like. All of which were, uh, transformed.

Please believe me: I haven't suddenly 'gotten in touch with my macho side'. I still think that bass, like government, is something which should be applied judiciously and in small doses. But the Q200E accomplishes something so rare amongst even the more pedigreed subwoofers that it deserves extra attention in the Land of the Small Two-Way. Quite clearly, the Q200E is so neutral and so clean that it inflicts little influence on the sonic character of the primary speaker...beyond adding bass. Those of you who prefer small speakers but who want more bass without reverting to a larger model have always been aware of the anticipated discontinuities between main and sub, especially when mixing brands. The REL blends seamlessly with so many speaker types that it's almost uncanny.

But, no, it's not a universal speaker add-on. The LS3/5As and the Genexxas appear to have cut-off points too high to merge perfectly with the Q200Es, however much they quite audibly benefited from lower octave reinforcement. But the next stage up - wow! Bursts with the old Quad ESLs, the Quad 77-10Ls, Sonus Faber Concertinos and the Apogee hybrids in my A/V set-up found near-instant synergy. With the exception of the old Quads, which were limited by absolute maximum output levels, it quickly emerged that a successful mating had less to do with tonal character or (as in the case of the tinier speakers) usable cut-off points than it did with speed. The REL is one fast little sucker, a trait better revealed in A/V mode than with pure music to the right of hip-hop. In every case, the speakers it worked best with were those with intrinsically snappy bass - whatever their lowest usable frequencies.

But then we get into the problem of role-playing, more than ever an issue when components such as the Q200E have to wear two hats: audio and video. REL supplied a brace of Q200Es for the review, because they argue quite rightly that you need two for convincing stereo bass. But it begs a question: who in his or her right mind would spend £1200 on subwoofers, when that amount added to the sort of speakers which justify augmentation by a lone subwoofer costing £600 must cost at least £1000? You don't add a £600 sub to a pair of £300 speakers; you buy a £900 full-range pair at the outset. Hence, I would rather have a £2200 pair of speakers than a £1000 pair plus two sub-woofers.

Which leads me to the Q200E's real purpose - indeed, the true rationale behind all subwoofers: home theatre. I found greater worth in the REL's presence when playing DVD films than when listening to two-channel, pure music program material. OK, so this may be a personal quirk, and everyone has the right to switch on their subs whether they're listening to cinematic events or straight music; I just happened to prefer the audio-only sessions without the subs, while I kept them thumping away during DVD video playback.

Naturally, the first thing I tried was the sandworm summoner in , which took on more weight, greater impact and - certainly - tighter transient control with the REL in place. As for the volcanic rumblings in (the DTS version), they seemed deeper and more thunderous. But the moment which sold me on the REL for A/V use was the buffalo stampede in : a room-filling wash of bass signal that crawled across the floor and rattled everything in its wake. Switching off the REL mid-stampede proved a point Simon has been beating me over the head with for a decade: you don't know how much a subwoofer contributes until you switch it off.

This teensy cube is a minor miracle. I'll be the first to say that one should, if buying fresh, add the £600 to the primary speaker, because a good biggun' always hammers a small one. But if you have an existing system, or you're creating a 5.1 channel installation and you wouldn't mind saving some space, the Q200E is a no-brainer. You just buy one or two or even five. It's that easy.

But try not to look at it.