NAD Viso HP-50 Measurements

01
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NAD Viso HP-50 Frequency Response

NAD HP-50 frequency response
Brent Butterworth

Here's how I measured the performance of the Viso HP-50. I used a G.R.A.S. 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  calibrated the measurements for ear reference point (ERP), roughly the point in space where your palm intersects with the axis of your ear canal when you press your hand against your ear -- and about where the face of the HP-50's driver baffle would sit when you wear it. I moved the earpads around slightly on the ear/cheek simulator to find the position that gave the best bass response and the most characteristic result overall.

The chart above shows the frequency response of the HP-50 in the left (blue) and right (red) channels. This measurement was taken at a test level referenced to 94 dB @ 500 Hz, as recommended in the IEC 60268-7 headphone measurement standard. There is little agreement about  what constitutes a "good" frequency response in headphones, but this chart does let you get an objective impression of how the HP-50 is tuned.

The HP-50's response looks relatively flat when compared with most headphones I've measured, with a mild and very broad boost in the treble between 2 kHz and 8 kHz. The difference in bass response of the two channels is probably due to differences in fit on the ear/cheek simulator; both represent the best bass response I was able to get from each channel.

Sensitivity of the HP-50, measured with a 1 mW signal calculated for the rated 32 ohms impedance and averaged from 300 Hz to 3 kHz, is 106.3 dB.

02
of 07

NAD Viso HP-50 vs. PSB M4U 1

Frequency response NAD VP-50 versus PSB M4U 1
Brent Butterworth

The chart here shows the frequency response of the HP-50 (blue trace) compared with the PSB M4U 1 (green trace), which was also voiced by Paul Barton. As you can see, the measurements are very similar, with the HP-50 having slightly less energy around 1 kHz and slightly more energy around 2 kHz.

03
of 07

NAD Viso HP-50 Response, 5 vs. 75 Ohms

NAD Viso HP-50 5 versus 75 ohms source
Brent Butterworth

Frequency response of the HP-50, right channel, when fed by an amp (Musical Fidelity V-Can) with 5 ohms output impedance (red trace), and with 75 ohms output impedance (green trace). Ideally, the lines should overlap perfectly -- as they do here -- which shows that the HP-50's tonal character won't change if you connect it to a low-quality source amplifier, like the ones in most laptops and cheap smartphones.

04
of 07

NAD Viso HP-50 Spectral Decay

NAD Viso HP-50 cumulative spectral decay
Brent Butterworth

Spectral decay (waterfall) plot of HP-50, right channel. Long blue streaks indicate resonances, which are generally undesirable. This headphone shows very narrow (and probably only slightly if at all audible) resonances at 1.8 kHz and 3.5 kHz.

05
of 07

NAD Viso HP-50 Distortion

NAD HP-50 THD
Brent Butterworth
Total harmonic distortion (THD) of the HP-50, right channel, measured at a test level set by playing pink noise at an average level 100 dBA. The lower this line is on the chart, the better. Ideally it would overlap the bottom border of the chart. Distortion of the HP-50 is extremely low, among the best I've measured.
06
of 07

NAD Viso HP-50 Impedance

NAD Viso HP-50 impedance
Brent Butterworth
Impedance of the HP-50, right channel. Generally, impedance that is consistent (i.e., flat) at all frequencies is better. The HP-50's impedance is relatively flat, averaging 37 ohms.
07
of 07

NAD Viso HP-50 Isolation

NAD Viso HP-50 Isolation
Brent Butterworth

Isolation of the Viso HP-50, right channel. Levels below 75 dB indicate attenuation of outside noise -- i.e., 65 dB on the chart means a -10 dB reduction in outside sounds at that sound frequency. The lower the line is on the chart, the better. The HP-50's isolation is outstanding for a passive over-ear headphone, reducing outside sounds by -15 dB at 1 kHz and by as much as -40 dB at 8 kHz. Note that there's no significant reduction at frequencies below 200 Hz, so the HP-50 won't do much to cut out jet engine noise.