B&W 603 loudspeaker Lab Report

It's a notable feature of modern B&Ws that they don't have particularly flat frequency responses – even the 800 D3 series. So it is no surprise to find that the 603's forward frequency response [Graph 1, measured at 1m on the tweeter axis] is on the uneven side, although it is unexpected to see the deep if narrow notch just below 6kHz. This has the effect of increasing the response errors to a high ±6.1dB and ±6.0dB respectively, well outside B&W's claimed ±3dB. Despite this, pair matching is excellent at ±0.6dB over the same 300Hz-20kHz frequency range. Diffraction-corrected near-field measurement showed the bass response to reach 52Hz (–6dB re. 200Hz) – typical for a floorstander of this size although shy of B&W's 29Hz spec.


Forward response is not especially flat, and the deep notch at 6kHz certainly unexpected


Cabinet modes are well suppressed as are any resonances associated with the Continuum mid driver

B&W's claim of 88.5dB sensitivity we couldn't quite match either, our measured 88.1dB on pink noise and 87.6dB with a 'music-shaped' noise spectrum suggesting that 88dB is perhaps more realistic. Low impedance is used to help achieve this, the measured 2.7ohm minimum modulus belying both the 8ohm nominal rating and B&W's quoted 3ohm minimum. Large impedance phase angles at low frequency drop the EPDR (equivalent peak dissipation resistance) to a very low minimum of 1.1ohm at 92Hz, with further dips to 1.6ohm at 736Hz and 2.0ohm at 10.5kHz completing the picture of a loudspeaker that is notably challenging to drive, particularly at this price point.

As usual with B&W, total harmonic distortion is low at 100Hz, 1kHz and 10kHz – certainly lower than many competitors. The cumulative spectral decay waterfall [Graph 2] is pretty clean, the Continuum driver displaying only a few well-damped treble resonances. KH

Sensitivity (SPL/1m/2.83V – Mean/IEC/Music): 88.8dB / 88.1dB / 87.6dB
Impedance modulus: minimum & maximum (20Hz–20kHz): 2.7ohm @ 129Hz / 29.3ohm @ 53Hz
Impedance phase: minimum & maximum (20Hz–20kHz): –75° @ 64Hz / 51° @ 1.3kHz
Pair matching/Resp. error (300Hz–20kHz): ±0.6dB / ±6.1dB / ±6.0dB
LF/HF extension (–6dB ref 200Hz/10kHz): 52Hz / >40kHz / >40kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m): 0.4% / 0.1% / <0.1%
Dimensions (HWD) / Weight (each): 985x190x340mm / 24kg
Price:: £1249

B&W Group Ltd
West Sussex
0800 232 1513