Loudspeakers

Another day in lockdown, and another Zoom call, this time with Editor PM 'meeting' KEF's Head of Acoustics, Jack Oclee-Brown. Metamaterial is the buzzword, but it doesn't define the latest LS50 – that honour still goes to the Uni-Q coincident driver array with its distinctive 'Tangerine' waveguide. For example, the central tweeter is composed of aluminium alloy, not beryllium or 'diamond', and yet its breakup mode is deferred to a high 40kHz (~30kHz is typical).

'This all stems from our work on the Muon project', reveals Jack, 'a spherical dome is required to optimally load the Tangerine waveguide, but an elliptical cross-section yields greater stiffness. We combined both in the Uni-Q tweeter, and a very stiff triangular section is formed where the two parts join.

'We've evolved the Uni-Q driver and motor over its long lifetime, but one big change in the Meta is our new crossover design. The transfer function/slopes are 4th-order electrical/acoustic (combined) and yield much improved on- and off-axis smoothness.' [See Lab Report, p63.]

Will we see metamaterials in other KEF speakers? 'The timescale is uncertain but, yes, "mets" will undoubtedly move out to our other speakers', says Jack. 'More importantly, the new streaming platform used in the LS50 Wireless II will be a big part of our product story in the coming year. We are also very keen to do more than simply make a passive speaker active, and our little KC62 subwoofer gives a glimpse of what is possible.' PM