Headphones

We tested the PX exclusively via its analogue input with noise cancelling off. As its gain controls operate only with digital signals, it necessarily has a fixed sensitivity: we measured 117.5dB for 1V input at 1kHz, averaged for the two capsules, so with an analogue source it acts like a conventional headphone with slightly above-average sensitivity. The difference is that the PX has higher input impedance – around 850ohm – so draws much less drive current. A surprise was discovering that the PX is polarity inverting. You can argue all you like about whether this is audible or not, but the plain fact is it shouldn’t be the case. Previous B&Ws that we’ve measured [P3; P7, HFN Aug ’14; P9 Signature, HFN Mar ’17] have all been characterised by tonal balances which strongly favour lower-midrange and bass, and the PX is a chip off the same block.

The uncorrected frequency responses [Graph 1] are rather different at low frequencies for the two capsules, suggesting a sealing issue with the right side. No matter how carefully it was placed on the artificial ear, it never matched the LF output of the left capsule – which presumably demonstrates the intended response. The hump in output below 900Hz is obvious, as is a lower, narrower peak at 2-3kHz than conventionally considered necessary to achieve neutral tonal balance.

Because of this LF disparity, the third-octave corrected responses [Graph 2], which are based on the average of the two capsule responses, are if anything less fulsome in the bass than they should be but still demonstrate an obvious lower-mid/bass excess. The perceived frequency response above 1kHz is much flatter but for the expected dip around 3kHz. Not indicated in any of the measurements is that the PX – again in line with previous B&Ws – has headband vibrational issues at LF, although it lacks the higher frequency ping previously caused by thin wire capsule hangers. KH

Sensitivity (SPL at 1kHz for 1Vrms input): 117.5dB
Impedance modulus min/max (20Hz-20kHz): 846ohm @ 20kHz / 904ohm @ 20Hz
Capsule matching (40Hz-10kHz): ±10.4dB
LF extension (–6dB ref. 200Hz): 22Hz
Distortion 100Hz/1kHz (for 90dB SPL): 0.1% / 0.4%
Weight (inc cable): 350g
Price: £329