Floorstanding loudspeakers — KEF Q550

The Q550 is the smallest floorstanding speaker of KEF's 2017 Q Series, the eighth generation of the company's entry-level hi-fi range, priced at USD 550 per speaker at launch. It is a slim 2.5-way design that uses the Uni-Q coaxial driver found across the Q line and sits below the larger Q750 and Q950 towers of the same generation, while the Q150 and Q350 were the stand-mount models of that release.

Key specs that matter

The Q550 carries a Uni-Q unit with a 25 mm vented aluminium dome tweeter inside a 130 mm aluminium cone, a separate 130 mm aluminium bass driver and two 130 mm auxiliary bass radiators. The crossover point is 2.5 kHz. Frequency response is 58 Hz to 28 kHz at ±3 dB, reaching 45 Hz at -6 dB. Sensitivity is 87 dB, impedance is 8 ohms nominal with a 3.5 ohm minimum, and KEF recommends amplifiers of 15 to 130 W. Maximum output is 110 dB. The cabinet measures 873 x 180 x 278 mm without its plinth and 926 x 299 x 310 mm with it, and weighs 14.5 kg. Two finishes were offered, black and white, both with a satin surface.

Engineering and use context

In a 2.5-way layout, both cones reproduce bass, but only the Uni-Q cone continues up into the midrange before handing over to the tweeter, so the lower driver adds bass output without affecting the midrange. KEF lists the Q550 as bass reflex, yet the low-frequency loading comes from the two auxiliary bass radiators, passive diaphragms driven by air pressure inside the cabinet, instead of a port. For the 2017 range KEF gave the ABRs a new surround and rear suspension to control them at high levels. The midrange section of the Uni-Q driver sits in its own closed enclosure, which keeps pressure from the bass cabinet off the cone. A damped loading tube behind the tweeter targets the lower treble, and the crossover uses a low-distortion inductor. The 180 mm wide front baffle keeps the cabinet unobtrusive.

Pairing

Its moderate sensitivity and impedance let the Q550 run from modest integrateds or surround receivers. The auxiliary bass radiators radiate from the cabinet itself rather than from a rear port, which makes placement near a rear wall straightforward. The Q550 can also form the front pair of a home cinema system with other Q Series models of the same generation.

Alternatives

The KEF Q7 Meta is a later Q Series floorstander, with a Uni-Q driver using MAT and two 165 mm bass drivers.