Headphone Reviews

Measurements Wired Active

Measurements Wired Active Noise Canceling On

Above I am only showing the wired responses. Measurements were taken in wireless modes but are much the same as the wired response. Measurements sheets are available here for Wireless Active and Wireless Noise Canceling modes.

Looking at the raw responses of the PSB M4U 8 in all modes you can see there is very little effect on response with movement on the head. But I do need to say I had to work fairly hard to ensure a seal at each measurement. I think this was more due to the materials and size of the measurement head than the headphones. I found no problem getting a good fit and seal on my head in listening.

You can see in the raw response in passive mode that the bass emphasis doesn't return to baseling until about 500Hz. This bass boost bleeding into the mids was quite audible. In both active and NC modes the bass boost is limited to around 150Hz by the RoomFeel EQ in DSP.

Bass quality as seen in the 30Hz square wave waveform top and low THD+noise seems quite good. In Active and NC modes the 30Hz square wave is more tilted due to the drop off below 20Hz, but has fairly good shape (little sway back). THD+noise rises in the active modes due to the added noise of the electronics, but the curve remains flat in the low frequencies apart from a minor increase in bass distortion at 100dB in NC mode.

Raw frequency response in passive mode above 600Hz has very good shape, and were it not for the bass boost bleeding into the midrange overshadowing the perceived character of these cans this would easily be the best sounding mode of operation due to it's excellent response above 600Hz.

In Wired Active mode, raw response starts rising at about 600Hz towards the peak at 3.3kHz. The shape of this curve is good, but the overall amount of emphasis is about 5dB too high, which can be seen in the bump between 1kHz and 4kHz on the compensated response plot. It can also be seen as excessive ringing on the leading edge of the 300Hz square wave. Some clean ringing at 3kHz at the leading edge can be virtually inaudible (as with the Sennheiser HD 650) but the M4U 8 is a bit excessive. Point is, while this is not ideal, it's also not as bad as it looks in listening.

Response drops off rapidly above 4kHz and is probably a few dB low between 4kHz and 8kHz. Fortunately, this is an area where you're better off having too little rather than too much energy as these frequencies can be quite annoying if over-done.

Raw response in Noise Canceling mode is largely the same as active mode but for a significant feature between 1kHz and 2kHz. This change was clearly audible when switching modes as an increased high frequency hootiness...sounding something like a person who has a little whistle with their "S" sounds.

Distortion is fairly low in passive mode, and increases in distortion in active and NC mode will largely be due to increases in noise of the active electronics circuits.

Passive isolation in passive and active modes is fairly good for a headphone of this type. Increases in low frequency isolation is pretty dramatic, but some loss of isolation in mid and high frequencies also occurs. Still this is a good result, though not quite as good as the Bose QC35.

Needing only 13mVrms, 20mVrms, and 43mVrms to achieve 90dBspl at the ear in NC, Active, and Passive modes respectively, this headphone will play quite loud out of a portable device.