Headphones

Audio-Technica quotes the ATH-ADX5000’s sensitivity as 100dB SPL for 1mW, equivalent to 103.8dB for 1V across the specified nominal impedance of 420ohm. This is the better part of 2dB less than the 105.7dB we measured at 1kHz, averaged for the two capsules, but the ADX5000 still rates as a low-sensitivity headphone in today’s market context, about 10dB shy of what we typically measure from medium-impedance models. With a pukka headphone amplifier, though, this will not preclude the achievement of short-term peak levels of 120dB on high dynamic range programme provided that the maximum output capability is at least 5.2V.

Impedance more than doubles from a minimum of 397ohm to a maximum of 817ohm (20Hz-20kHz), but this high load ensures that any frequency response errors caused by the finite source impedance of the headphone amplifier are small: 0.11dB driven via a 10ohm source or 0.32dB from a 30ohm source. But the impedance vs. frequency measurement showed a strange effect I haven’t experienced from a headphone before. Here the trace was rough below about 800Hz and wasn’t smoothed by long averaging, suggesting that the structure of the ADX5000 is unusually resonant. Ripples higher up the frequency range suggest other resonances at about 2.2kHz, 3.5kHz, 4.9kHz and 7.4kHz, all verified by a CSD waterfall test (not shown).

Uncorrected frequency responses for both capsules [Graph 1] are saddle-shaped below 1kHz with peaks at 3.5kHz, a little higher in frequency than expected. Corrected frequency responses [Graph 2] show that this saddle helps flatten the Harman-corrected response [red trace] down to about 150Hz, below which output drops off. Above 1kHz the Harman and diffuse-field corrections show an initial dip in the lower treble followed by stronger output thereafter, which may leave the upper treble sounding rather exposed. KH

Sensitivity (SPL at 1kHz for 1Vrms input): 105.7dB
Impedance modulus min/max (20Hz-20kHz): 397ohm @ 2.4kHz / 817ohm @ 92Hz
Capsule matching (40Hz-10kHz): ±5.0dB
LF extension (–6dB ref. 200Hz): 17Hz
Distortion 100Hz/1kHz (for 90dB SPL): 0.2% / <0.1%
Weight (inc cable and 0.25in connector): 358g
Price: £1990