KEF R3 loudspeaker Lab Report

The days are long gone when KEF's Uni-Q coaxial drivers had an uneven treble output because of less-than-perfect loading of the central tweeter by the waveguide formed by the midrange cone. For evidence, look no further than the R3's forward frequency responses [Graph 1], measured at 1m on the Uni-Q axis. The response errors are ±2.0dB and ±2.1dB respectively – remarkably, a tad better than we measured from the DSP-active Kii Three over the same 200Hz-20kHz [HFN Aug '18], although the R3 cannot match the latter's stunning ±1.1dB below 12kHz. The R3 also just betters the Three's pair matching error at ±0.7dB over the same frequency range, albeit not its unprecedented ±0.3dB below 15kHz. In short, the R3's frequency response is amazingly flat for a passive design – flatter than that of the ELAC Adante AS-61 (±3.3dB) which it superficially resembles [HFN Feb '18].


The R3 boasts a remarkably flat and extended response for a passive loudspeaker of limited size


Cabinet, bass and Uni-Q drivers are also well controlled with v. mild modes just visible in the treble

The R3 also betters the AS-61 for sensitivity (86.1dB versus 83.4dB) and slightly for bass extension too (40Hz versus 46Hz, –6dB re. 200Hz), although the R3's LF output is shelved down by about 6dB below 100Hz until rolling off rapidly below 40Hz. Low impedance is exploited to achieve this: the R3's 3.1ohm minimum modulus making it a true 4ohm design, while its phase angles drive the EPDR (equivalent peak dissipation resistance) down to a low of 1.5ohm at 39Hz, with another dip to 2.2ohm at 226Hz. So the R3 is demanding of its amplifier! Another indication of how skilfully KEF has contrived the cone flare and surround design to prevent treble reflections without paying the price of compromised bending stiffness is the CSD plot [Graph 2], which evinces only low-level treble resonances. KH

Sensitivity (SPL/1m/2.83Vrms – Mean/IEC/Music): 86.1dB / 86.1dB / 86.1dB
Impedance modulus min/max (20Hz–20kHz): 3.1ohm @ 44Hz / 13.1ohm @ 2.4kHz
Impedance phase min/max (20Hz–20kHz): -42° @ 37Hz / 32° @ 1.3kHz
Pair matching/Response Error (200Hz–20kHz): ±0.7dB / ±2.0dB / ±2.1dB
LF/HF extension (–6dB ref 200Hz/10kHz): 40Hz / >40kHz / >40kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m): 0.5% / 0.2% / 0.1%
Dimensions (HWD) / Weight (Each): 421x200x312mm / 14kg
Price: £1300

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