Floorstanding loudspeakers — Graham Audio LS5/1

The LS5/1 is a floorstanding monitor from Graham Audio, the British maker of BBC-derived loudspeakers, and it recreates a BBC design of the 1960s built around a single 15 inch bass and midrange driver and two tweeters. The original used commercially available units from Plessey and GEC. Derek Hughes designed the Graham version, and the first prototype cabinets reached the company in March 2020, with the launch planned for after the pandemic. The 2022 European price was EUR 22,050 per pair.

Key specs that matter

A 380 mm slot-loaded bass and midrange driver works with twin 25 mm soft-dome tweeters, joined by a 22-element crossover at 1.6 kHz. The reflex enclosure has its port on the front. Response is 37 Hz to 18 kHz within 3 dB, sensitivity is 89 dB SPL for 2.83 V at 1 m and impedance is 8 ohm. Maximum output is more than 110 dB for a pair at 2 m. Each cabinet measures 43 cm wide, 103 cm high and 48 cm deep and weighs 42 kg. Standard veneers are cherry, oak, walnut, rosewood and ebony, with teak and sprayed finishes available by request.

Engineering and use context

The BBC needed two tweeters in the LS5/1 to reach the required power handling. In this model the upper tweeter rolls off at higher frequencies, which avoids the lobing that occurs when two sources produce the same output at a spacing comparable to the wavelength. The smaller outside broadcast variant, the LS3/1, used a sealed box and placed the tweeters in front of the woofer instead. A woofer of 15 inches is very rare in home loudspeakers today, and Graham states that its modern unit has much higher power handling and wider bandwidth than the Plessey original. Such a large cone becomes directional near the top of its range, so the BBC slot-loaded it, a method Graham also applies in its LS5/5. The slot makes the driver behave like a smaller one, so its dispersion stays wider up to a higher frequency and the off-axis response is more even, which makes a big driver usable in a typical domestic listening room. The damped MDF cabinet uses mass-loaded thin panels to keep resonance low, in line with the BBC approach.

Pairing

Graham recommends 50 to 250 W of unclipped programme power. Its efficiency and even impedance mean moderate valve amplifiers can drive it, while high-powered solid-state designs make use of its output capability. Given its weight, the speaker stands directly on the floor.

Alternatives

The Graham LS4/4 is a slimmer three-way floorstander in the same range, using a 270 mm bass unit and a separate 200 mm midrange.