Headphones

After a succession of planar magnetic designs, many of which have had relatively low voltage sensitivity (or worse), the K371 serves as a reminder of how this is rarely an issue with medium impedance moving-coil headphones. In fact the K371's 120.6dB SPL for 1V at 1kHz, averaged for the two capsules, makes it the most sensitive headphone we've tested this year. And despite the K371 being a moving-coil rather than a planar magnetic design, AKG has managed to contain its impedance variation within quite tight limits of 35.0-40.0ohm (20Hz-20kHz).

As a result, modification of the final frequency response due to the finite source resistance of the driving headphone amplifier is modest, amounting to 0.24dB with a 10ohm source and 0.51dB with a 30ohm source. Uncorrected frequency responses for the two capsules [see Graph 1, below] are more than usually disparate. The right capsule (red trace) shows the expected shelving up at LF to follow the Harman target response, and has quite a strong peak at 2.5kHz to deliver a neutral perceived tonal balance through the presence band. But with the left capsule both features are less prominent.

The outcome for the corrected responses [see Graph 2, below] is that all three (diffuse field, free field and Harman) show the K371 to have shelved-down treble above 1.5-3kHz. All also show a bass lift, which may seem surprising in the case of the Harman correction, but this is using the 2013 Harman target, not the latest 2017 target which shows the K317's perceived frequency response to be flat below 2kHz within +3/-2dB. Although, at the time of writing, I have yet to perform leakage measurements, response variability at LF suggests that the K371 will probably suffer bass loss if the earpad seal is compromised. Again in contrast to many planar magnetic designs, the moving-coil K371 delivered substantially clean CSD waterfalls, indicating few resonances, from both capsules. KH