Headphones

In most of the best noise cancelling (NC) headphones it is arranged that their frequency response remains largely unaltered whether NC is engaged or disabled, to ensure consistency of sound quality. But in the PX this is not the case. When the Environment Filter is set to ‘Office’ (the mildest of the three NC regimes) the PX’s frequency response does indeed remain the same as when the Filter is disabled. But on the two more effective NC settings – ‘City’ and ‘Flight’ – the frequency response, and hence the perceived tonal balance, changes markedly. Subtracting the responses results in a complex difference but, essentially, with ‘City’ or ‘Flight’ the PX’s output increases a little below 45Hz (+1.3dB at 20Hz) and a lot at two frequencies in the presence band: +2.5dB at 2.2kHz and +5.8dB at 3.4kHz. Elsewhere output is reduced, by an average of about 2.5dB from 100Hz to 1.6kHz and 3.5dB above 4.5kHz. Whichever tonal balance you prefer, the PX will not deliver it in all modes. KH