Headphones

AKG’s K3003i [HFN Apr ’12], predecessor to the N5005, was notable for having very high sensitivity – we measured 126.4dB SPL at 1kHz for 1 volt input – and a low, highly variable impedance which made it unusually susceptible to frequency response changes caused by headphone amps with anything other than a sub-1ohm source impedance. With the new N5005, AKG has to some extent learnt the lessons. Sensitivity is specified to be about 10dB lower at 116dB SPL for 1V at 1kHz, which is close to the 115.5dB we measured, averaged for the two channels. This is typical of modern over-ear headphones, so volume settings for the N5005 will be about the same. Nominal impedance is now 18ohm, our measurements recording a range of 13.7-24.7ohm (20Hz-20kHz). While this is an improvement over the 7.2-14.7ohm we measured for the K3003i, it is still sufficiently variable to result in a 1.84dB change in frequency response when driven from an amp with a 10ohm source impedance, rising to 3.15dB with a 30ohm source impedance.

To hear the N5005’s intended tonal balance it is essential to use a source component with a very low output impedance. Uncorrected frequency responses for the two channels, both with the Reference Sound filter, show a prominent shelving up of its bass [Graph 1]. This would mean a very bass-heavy sound in an over-ear headphone but accords with the target response for in-ear headphones identified by Harman’s research. The four acoustic filters shelve the response above 1kHz up or down, to the tune of –2.4dB/3kHz for the Bass Boost filter, +2.7dB for the Mid High Boost filter and +5.0dB for the High Boost filter. The diffuse-field corrected response [green trace, Graph 2] suggests the perceived tonal balance will be hopelessly bass heavy while correcting the response to the Harman in-ear target [red] suggests a flat perceived response to within +2.6dB/–4.8dB, (20Hz-8kHz). KH

Sensitivity (SPL at 1kHz for 1Vrms input): 115.5dB
Impedance modulus min/max (20Hz-20kHz): 13.7ohm @ 13kHz / 24.7ohm @ 1.4kHz
Capsule matching (40Hz-10kHz): ±1.8dB
LF extension (–6dB ref. 200Hz): <20Hz
Distortion 100Hz/1kHz (for 90dB SPL): 0.5% / 0.4%
Weight (inc cable and 0.25in connector): 31g
Price: £800