REL T/7i Subwoofer and Arrow Wireless Module Review

The T/7i is described as a revision to the original T/7 but the nature and scope of these changes is sufficiently great that nobody would have batted an eyelid at it being described as a new model. The basic premise of the T/7i is the same as the T/7 in that it is a sealed cabinet design which uses an active driver mated to a passive radiator. The most significant revision between old and new is that the position of these drivers has been reversed. The 8 inch active driver now faces forwards while the 10 inch radiator moves to the underside.

In principle this makes a fair degree of sense. While a forward firing driver places some restrictions in placement terms over a downward firing one, it alleviates many of the issues of using such a device on a suspended floor – the energy from the passive radiator being somewhat lower than the driver – and, in many parts of the world, this is rather more useful than any slight loss of positioning flexibility.

The material that the drivers have been made from have also been changed. They are still in essence made from paper but REL has delved into the business of paper composition and worked to create a driver that has less mass to it. This feeds into REL’s ongoing concern with the ‘speed’ with which the driver operates. Reducing the mass of the driver, reduces the amount of force required to start and in turn stop it. The driver can be moved more precisely and under a greater degree of control than would be the case if it was heavier and more inert. To give the driver a rigidity greater than that of a soggy paper plate, REL has then fitted a very large aluminium centre cap to the active driver. This acts as a stiffening component which doesn’t add much in the way of mass to the product.

The cabinet these drivers are placed in has been thickened and strengthened. It is now made from inch thick sections of MDF and feels extremely solid to the touch. The feet are integral to the cabinet and are capped with a plastic screw fitting that seems to avoid them marking surfaces that they are placed on. Compared to some of the burlier American designs we have looked at in recent months, the T/7i feels less monolithic – it can be lifted without the nagging feeling that a hernia is only seconds away – but it still manages to come across as solid and inert.

It is the amplification and inputs of the T/7i where some of REL’s distinct design philosophies come into play. First up, on the amp plate you will encounter a heat sink which is a clear indicator that the amp used in the T/7i is a class A/B design rather than the more frequently encountered Class D. This generates 200 watts and is a gently evolved version of an amp used in many of the models dating all the way back to the very beginning of the company’s existence. The bald numbers don’t seem terribly exciting but in terms of current delivery and damping factor, there is much to be said for this approach.

This amp will work with both a dedicated LFE input and a high level connection that is the REL trademark. This is intended to take the feed from an amplifier's speaker terminals and – crucially – because there is no high pass filter on this connection, it will impart some of the character of your amp to your sub bass. REL states in the manual that even if the LFE connection is in use, the high level connection should still be connected for optimal performance. While this is a contentious area, even if I did go about doing this I would have to switch my front speakers to large, which isn’t how my equipment is set up. It does – even if we leave subjectivity to one side for a minute – allow for the connection of the REL to a stereo amp with no preout. REL supplies a cable for this purpose and a conversation with REL HQ suggests that specialist ones are also available.

The T/7i can also be supplied – as seen here – with the Arrow wireless module. This is a proprietary system developed by/for REL that consists of a USB powered sending unit and a self-powered receiver that attaches straight to an RS-232 connection on the rear panel of the T7i. REL says the system is lossless and has a maximum range of 13.7 meters. Pairing it is simple enough and once done, provided the T/7i has power running to it, it can be placed anywhere. Interestingly the receiver module has both LFE and high level connectors in a mirror of the input board. REL states that the benefits of the high level connection as laid out by them will still be experienced via wireless.

As is the now traditional incantation when discussing the aesthetics of subwoofers, there are limits to exactly what you can do with a solid box containing one or more hefty drivers. This being said, the T/7i feels like a special piece of equipment. The gloss black lacquer on the cabinet is applied to a very high standard and the REL badge on the top looks equally smart (and according to REL functions as part of the resonance control of the cabinet itself). While subwoofers don’t generally get put out on display, you could just about find justification for doing so with the T/7i. The level of overall build and finish is also extremely good and everything feels solid and carefully thought out.

There’s a ‘but’ coming though. At £850, the REL feels fairly pricey for the specification on offer. Ignoring the amplifier power for a moment as this is a slightly different area, some aspects of the REL feel a little lightweight. There is an ongoing argument about what equipment is required with subs and what is pure window dressing but I would have liked to see a continuously variable phase control – arguing you can place the T/7i wherever you like doesn’t really stand up when you have to take into account keeping it in phase with the supporting speakers. I’d also potentially like at least the option of remote control.

With the T/7i running at the front of the room on axis with the front speakers and running a 90Hz crossover, there are some immediate signs that the T/7i has some impressive qualities. Most notably, the integration that the REL offers between it and the Elipsons, even without the high level input in use, is seamless to the point of imperceptible. It is frequently impossible to work out what the T/7i is contributing until you switch it out of the circuit. If you have smaller speakers and will be dependent on a subwoofer to fill in all the time – and that means gently picking out the orchestral score for Victoria as much as it does delivering the thrills of movie night – the REL is a superb partner.

Of course, when it is movie night, the performance of the T/7i is good with some small caveats. Firstly, if you absolutely must feel the full brunt of any impact and explosion in your lower intestine, this is probably not the device for you. REL quotes a lower figure of 30Hz and this can be comfortably exceeded in room but this isn’t a truly seismic device. There are some rather better bits of news though. The detail retrieval of the REL is extremely good. The various effects that make up the movement of tanks in Fury is delivered with real texture and an appreciable sense of the engine, tracks etc. This is bass as a fully developed aspect of the soundtrack and not a simple noise engine.

The truly outstanding quality of the REL comes to the fore when you put on something like the final live performance in Whiplash. This isn’t seismic bass, it can be handled almost in its entirety by a large floorstander, but with a 90Hz crossover a huge amount of the drumming is given over to the REL and it excels. In terms of sheer transient speed, the REL is able to match the Eclipse TD520SW – which is still the most accomplished subwoofer I have ever tested. REL’s obsession with driver weight and effective mass might seem curious but it really does pay dividends.

So what happens if you add a second one? Doubling the radiating area and keeping them both on axis allows for the same SPL numbers to be achieved with both subs running at lower levels. Performance below 30Hz is definitely enhanced. There is also the potential to even out the response in room by positioning them (lack of phase correction not withstanding). The same speed and detail is retained though and this makes for a seriously impressive sub bass system. It is a fairly expensive one though. Even though the individual cabinets are fairly compact, collectively, they take up more room than a single large one (and need two mains leads, two sub outputs etc). This is an answer to a specific set of design challenges, not a one size fits all solution.

The Arrow wireless system is genuinely impressive though. Using one T/7i via a standard wired connection and one via Arrow shows no performance difference or latency issues. It has proved completely bulletproof in the time it has been installed and this has included interrupting the power and other issues. £200 for the system isn’t cheap (and it needs power of its own) but it does work exactly as specified making the T/7i an impressive bit of kit.

When I reviewed the original T/7, I grudgingly conceded that, even as someone that isn’t a fan of using subs for music it was extremely good. The T/7i effectively builds on this. With a 55Hz crossover set on the sub to partner the AE1 Classics, the performance has the same seamless detailed and musical presentation that there was before but with an added dose of agility. The complex percussion line of The Comet is Coming’s Channel the Spirits are handled with enough speed and lack of overhang to be convincing and believable. There is a slight but perceptible sense of the character of the amp that helps bind the speakers and sub together that also helps.

Inserting the Arrow system into the chain and continuing to use the high level connection does seem to continue to convey the basic character of the amp in the signal and – as with multichannel use – has no effect on latency. Adding the second sub and giving each T/7i its own specific channel further improves the separation and detail and gives well recorded material an additiona boost. Once again, it’s expensive (although not as expensive as a single Eclipse TD520) but it does deliver aspects of performance that a single hefty sub simply can’t do.