Tuesday, September 26, 2017

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I measured the Bowers & Wilkins P5 Series 2s using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-Can headphone amplifier. I moved the headphones around to several different locations on the ear/cheek simulator to find the spot that gave the most bass and the most characteristic response. As I usually do with on-ear headphones, I used the ear/cheek simulator’s clamping mechanism to ensure a good seal. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

Frequency response

This chart shows the P5 Series 2s’ frequency response. Its obvious distinguishing characteristic is the big dip in the midrange, centered at 500Hz. That peak, centered at 2.3kHz, is broad and high in amplitude, leading me to speculate that many listeners will find the P5s to sound a little bright. You may notice the disparity in bass response between the left (blue) and right (red) channels. That’s the best bass output I could get from the left channel after repeated repositionings of the earpiece, but keep in mind that the acoustical mating of the ear/cheek simulator to on-ear models is too fussy and unpredictable for me to take off points here.

Frequency response

Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp has little effect on the P5 Series 2s other than a boost in the bass of about 1dB below 80Hz.

Frequency response

This chart compares the P5 Series 2 with a well-regarded on-ear model, Beyerdynamic’s T51p (red trace), as well as my reference headphones for the $300 price point: NAD’s Viso HP50s (green trace). These are normalized to 94dB at 500Hz, per my standard practice for headphone frequency-response measurements and as mandated by the IEC’s 60268-7 standard, which makes it look as if the P5 Series 2s have a lot more bass and treble output than the other headphones -- but it’s more accurate to think of them as having a huge midrange dip around 500Hz.

Waterfall

The P5 Series 2s’ waterfall plot looks very clean, with no noteworthy resonances.

THD

The total harmonic distortion (THD) of the P5 Series 2s is typical for on-ear ’phones. At the loud listening level of 90dBA (measured with pink noise), the THD rises to 2% at 20Hz, which you’re very unlikely to notice (unless you often listen to Saint-Saëns’s “Organ Symphony”). At the very loud listening level of 100dBA, the THD runs about 4.5% below 40Hz.

Isolation

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. With very little reduction of level in sounds below 1kHz, and none in the “jet engine band” of about 50-100Hz, this is typical performance for passive on-ear headphones.

Impedance

The impedance of the P5 Series 2s is mostly flat, staying between 24 and 30 ohms through the entire audioband.

The sensitivity of the P5 Series 2s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 22 ohms impedance, is 101.2dB. This is typical for on-ear headphones.

. . . Brent Butterworth
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