REL’s Serie T/x subwoofers, side by side. Here is the T/7x alongside the smaller T/5x and the flagship T/9x, showing what your money buys at each step.

The T/7x is the middle model of Serie T/x and the first REL rated for a medium-sized room. It moves from the sealed, down-firing layout of the T/5x to a front-firing 8-inch driver working with a larger 10-inch passive radiator in the base, and nearly doubles the amplifier power. The result is a subwoofer that still fits beside a sideboard but plays deeper and with far more authority than its size suggests. It is designed for two-channel music first, with enough in reserve for a living-room television, and it is the model in the range where depth, speed and output are most evenly balanced.

Brief product overview
The T/7x uses a front-firing 200mm (8-inch) long-throw FibreAlloy driver, a paper and aluminium composite cone with an inverted alloy centre cap on a steel chassis. It works with a down-firing 250mm (10-inch) passive radiator made from the same material. The passive radiator is an unpowered cone driven by air pressure inside the cabinet: it extends the bass the way a port would, but without port noise, and lets a compact box reach lower. Power comes from a 200-watt MOSFET Class A/B amplifier with a large toroidal power supply, and bass extends to 30Hz at −6dB in-room. Inputs are REL’s high-level Neutrik Speakon connection from the amplifier’s speaker terminals, a low-level RCA input and a dedicated .1/LFE input with its own level control. There is a phase switch, a standby switch on UK units, and optional Arrow wireless. The cabinet is finished in five coats of piano black or gloss white lacquer, measures 356mm wide, 320mm high and 363mm deep, and weighs 17.5kg.

How it sounds
Against the T/5x, the T/7x adds depth and weight without giving up speed. The passive radiator carries the lowest notes with real physical presence, while the lightweight active driver keeps bass lines quick and well timed, so it follows fast music as closely as slow orchestral swells. Fed through the high-level connection, it takes on the tonal balance of the main speakers and disappears into the soundstage once set up. What you notice is a larger, more stable image, more ambience around instruments, and standmounts that sound as though they have grown into floorstanders. It has enough output to give films real weight in a living room, though the lowest effects in a large room are better left to the T/9x or a Serie HT model.

What we’d partner it with
The Revival Audio Atalante 3 is a natural partner. It is a two-way standmount with a 180mm basalt-sandwich woofer and a 28mm soft dome tweeter with Revival’s ARID anti-reflection design, quoted to 44Hz and rated by Revival for rooms of 15 to 35 square metres, which matches the room the T/7x is designed for. Its 87dB sensitivity and 6-ohm load are easy to drive, and the T/7x takes over below the Atalante 3’s range to carry the system into the low 30s. The Fyne F1-5 (87dB, 8 ohms) is a more compact alternative with Fyne’s IsoFlare point-source driver. The Wharfedale Linton, a three-way heritage standmount with an 8-inch woofer, is a larger one that already goes deep and gains mostly in scale and control.

For amplification, the Hegel H120 is a 75-watt-per-channel Class AB integrated with Hegel’s SoundEngine 2 feed-forward circuit, a damping factor above 2000 that gives it firm control of the bass driver, its own DAC, and streaming via AirPlay, Roon Ready, Spotify Connect and UPnP. It has balanced and unbalanced analogue inputs, coaxial, optical and USB digital inputs, and a headphone output. It has no phono stage, so a turntable needs one such as the Rega Fono MM. The Hegel H95 is a lower-powered alternative in the same style. The Arcam SA45 costs more but adds 180 watts, MM and MC phono inputs and Dirac Live room correction. The T/7x is supplied with a 10m Speakon lead for the high-level run. For the main speakers, use a well-made cable of appropriate gauge; AudioQuest and Chord are the cable brands we stock.

Who shouldn’t buy it
If your room is small and your speakers are compact, the T/5x gives much of the same integration for less and takes up less floor space. If your room is large or open-plan, your main speakers are substantial floorstanders, or film is as important as music, the T/9x adds a 10-inch active driver, 300 watts and extension to 27Hz. For a system built mainly around film, the HT/1205 MkII puts 500 watts behind a 12-inch driver for the lowest effects. And if one T/7x cannot fill the room evenly, a stereo pair, one near each speaker, is REL’s own suggestion before moving up the range.

Start with the T/7x in a corner behind one of the main speakers, the active driver facing into the room and the feet in place, since the passive radiator fires down and needs the gap beneath the cabinet. Move it in small steps along the wall until the bass sounds even and the sub is hard to locate. Connect the Speakon lead to the amplifier: red to the left positive terminal, yellow to the right positive, and black to a negative terminal. That is REL’s standard wiring for a conventional Class AB amplifier such as the H120. Leave the main speakers running full range. Set the crossover close to where they roll off, then raise the high-level volume until the bass is felt rather than heard. Try both phase positions and keep the one that sounds fuller at the listening seat. A television’s subwoofer signal can go to the .1/LFE input, which has its own level control and leaves the music settings untouched. On UK units, the standby switch sets whether the T/7x sleeps when idle. The optional Arrow wireless system replaces the cable if the run is impractical.