Полочная акустика — KEF LS50 Meta

The LS50 Meta is a KEF passive two-way standmount, announced in September 2020 as the first speaker to use Metamaterial Absorption Technology (MAT). The technology came out of a two-year research and development collaboration between KEF and Acoustic Metamaterials Group. The speaker is sold in four colours with a silky matte surface - Carbon Black, Mineral White, Moss Green and Sand Shell - at a US price of USD 1,599.99 per pair.

Key specs that matter

The 12th generation Uni-Q array places a vented 25 mm aluminium dome tweeter backed by MAT in the middle of a 130 mm aluminium cone that handles bass and midrange, and the crossover sits at 2.1 kHz. KEF quotes a frequency response of 79 Hz to 28 kHz within plus or minus 3 dB, a frequency range of 47 Hz to 45 kHz and an in-room bass response of 26 Hz at -6 dB. Sensitivity is 85 dB for 2.83 V at 1 m. Nominal impedance is 8 ohm with a minimum of 3.5 ohm, and maximum output is 106 dB at 1 m. Distortion is below 0.4 percent from 175 Hz to 20 kHz and below 0.1 percent from 300 Hz to 10 kHz at 90 dB and 1 m. Each cabinet measures 302 x 200 x 280.5 mm (height, width, depth), weighing 7.8 kg.

Engineering and use context

MAT is a circular plastic structure placed behind the tweeter dome. Maze-like channels run through it, each of a different size and shape, so that every channel is tuned to absorb a different band of the rearward output. KEF states that it absorbs 99 percent of the unwanted energy from the rear of the driver, against around 60 percent for other approaches. The front baffle is injection-moulded from Dough Moulding Compound (DMC) and curved to lower diffraction, while the rear panel is recessed. Inside, cross-bracing is combined with Constrained Layer Damping. The bass reflex port is a patented offset flexible design shaped with the help of CFD flow simulation software. Rubber feet and port bungs are packed alongside a user manual and warranty information, and KEF offers S2 Floor Stands colour matched to the four finishes.

Pairing

KEF lists a recommended amplifier power of 40 to 100 W. The modest efficiency and the dip well below the nominal impedance favour a solid-state amplifier that stays stable into lower loads over a small low-power valve unit.

Alternatives

The KEF R3 Meta is a larger three-way bookshelf model from the R Series that also uses a Uni-Q driver with MAT.