KEF Blade One Meta Loudspeaker Lab Report

Lab Report

While attention is inevitably focused on the efficacy of KEF's Meta disc in dissipating the Uni-Q driver's rear-radiation [see LS50 Meta, HFN Jun '21], the Blade One Meta's driver ensemble delivers a remarkably flat axial response [see Graph 1]. With response errors of just ±1.2dB and ±1.3dB, respectively, coupled with a precise 0.45dB pair matching (all re. 200Hz-20kHz), the Blade One Meta faces competition from a mere handful of active, DSP-corrected speakers [see HFN Apr '20] in the quest for 'flatness'. On the other hand, the extreme ultrasonic treble resonance at 40kHz [+16dB re. mean midband output, pink shaded area] is specific to the Uni-Q driver, this breakup mode successfully deferred by a good 10kHz or so courtesy of the dome's hybrid spherical/elliptical profile. It is clearly visible on both the forward response and CSD waterfall [Graph 2], the latter also illustrating the very 'clean' and quick decay of mid and treble – a likely benefit of its Meta technology.

The flat response also makes for an accurate and subjectively relevant sensitivity of 88.5dB (1kHz) and 88.3dB (500Hz-8kHz), figures in tune with KEF's rated 88dB. Bass extension, too, is impressive at 34Hz (–6dB re. 200Hz), the 46Hz-350Hz (–6dB) output of the quad woofers combining with the slickly judged 26Hz port tuning [green shaded area, Graph 1]. Bass distortion is also very low at ~0.1% (re. 90dB SPL), but all this performance is gained at the expense of a fairly tough load, the impedance modulus dropping to just 2.5ohm/500Hz with max. phase angles of –57°/22Hz and +52°/1kHz. The toughest ±47°/4ohm regions occur in the low bass (24Hz) and midrange (840Hz). PM


Response including nearfield summed bass drivers/ports [green], freefield corrected to 1m at 2.83V [yellow], ultrasonic [pink]. Left, black; right, red


Uni-Q tweeter’s HF resonance dominates the waterfall, but the mid is ‘scrubbed clean’ by Meta

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 88.5dB / 88.3dB / 86.2dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 2.5ohm @ 500Hz, 14.8ohm @ 19Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –57° @ 22Hz, +52° @ 1.02kHz
Pair matching/Resp. error (200Hz–20kHz) 0.45dB/ ±1.2dB/±1.3dB
LF/HF extension (–6dB ref 200Hz/10kHz) 34Hz / 27.5kHz/28.5Hz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.1% / 0.06% / 0.5%
Dimensions (HWD) / Weight (each) 1590x363x540mm / 57kg
Price £30,000-£33,000 (depending on finish)

GP Acoustics (UK) Ltd
Maidstone, Kent
Supplied by: GP Acoustics (UK) Ltd
01622 672 261