Loudspeakers

Look at the responses we’ve measured from B&W’s latest 800 series models [HFN Dec ’15, Mar ’16, Oct ’16 and Sept ’17] and you’ll see that not only are they quite uneven, but they also differ quite markedly from model to model. It’s no surprise, then, to find that the flagship of the new 700 Series has a distinctly uneven response too [Graph 1 below; at 1m on the tweeter axis]. Output between 1kHz and 10kHz is sufficiently uneven to lead to response errors of ±4.4dB and ±4.8dB respectively – rather high for a speaker of this pedigree. Unusually for B&W, the pair matching error is also quite high at ±2.1dB, although this is due to large tweeter disparities in the top audible octave; below 10kHz it drops to a commendable ±0.8dB.

Another established characteristic of loftier B&Ws is that they typically present a challenging load to the amplifier, and that is the case with the 702 S2 too. Its specified nominal impedance of 8ohm is incompatible with the quoted minimum of 3.1ohm, and we measured an even lower dip to 2.8ohm at 118ohm. Combined with very high phase angles at low frequencies, this results in the EPDR (equivalent peak dissipation resistance) falling to a low of 1.2ohm at 88Hz, and this is compounded by further dips to 1.6ohm at 850Hz and 2.0ohm at 10.3kHz, making the 702 S2 tough on amplifiers. The upside of this low impedance is that the 702 S2 recorded a pink noise sensitivity of 89.6dB, within a whisker of B&W’s 90dB specification. Diffraction-corrected nearfield measurements showed the bass extension to be 51Hz (–6dB re. 200Hz). A series of treble resonances is visible in the CSD waterfall [Graph 2] which are probably caused by breakup in the cone of the Continuum midrange driver. KH

Sensitivity (SPL/1m/2.83Vrms – Mean/IEC/Music): 89.8dB / 89.6dB / 89.5dB
Impedance modulus min/max (20Hz–20kHz): 2.8ohm @ 118Hz / 25.7ohm @ 58Hz
Impedance phase min/max (20Hz–20kHz): –70° @ 70 / 48° @ 1.4kHz
Pair matching/Response Error (300Hz–20kHz): ±2.1dB / ±4.4dB / ±4.8dB
LF/HF extension (–6dB ref 200Hz/10kHz): 51Hz / >40kHz / >40kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m): 0.4% / 0.1% / <0.1%
Dimensions (HWD): 994x200x337mm
Price: £3,299