The AKG K400 is a vintage mid-range open-back AKG headphone destined for enjoyment and home use. It sits between the K300 and the K500.
Like most AKG, it’s super light on the head. Pads are made of some fabric/cloth material, they can be a bit stiffer than (p)leather or soft velour.
The K400 is a close brother to the K500 (higher-end model) and sounds similar to the K401 and K501.
○ Release : 1991
○ Current status : Discontinued
○ Type : Over-ear / Open-back
○ Measured weight : 261g
○ Impedance : 120 Ohms
○ Sensitivity : ~90 dB/mW
○ Average used price : $70-100
The K400 is definitely a mid-centric headphone, with severe bass roll-off but it exhibits an interesting and pleasant experience despite major sonic flaws.
The bass is surprising, it’s not extremely bass-light, and below 80hz I can hear anything. Despite being light, I hear some major distorsion and “bloom” on very bassy tracks. Midrange is forward with an emphasis in the presence region similar to the Sennheiser HD600, but even stronger. Vocals are extremely lively. Sometimes the upper-midrange (especially around 1.5-2.5khz) can sound shouty. For long listening sessions, I need to EQ down this region by 3-4 dB.
Treble is overall smooth but still manage to have some annoyance and harshness around 5-8 khz. Measurements show strong peak and ringing in that region, especially at 8Khz. It also lacks a bit of sparkle above 10khz.
Technicalities are just good, but below current mid-fi headphones (HD600/6XX, DT880, etc). The best feature of this headphone is definitely its soundstage ; it’s wide and tall, and easily beats most open-back cans I had the occasion to hear. The K400 sounds very open despite the lack of air. However, dynamics and decay are rather average. It’s somehow slow and soft sounding.
This AKG is part of the vintage K300s/K400s/K500s family from the 90s. The K400 can be bought used for around $90 (and cheaper in Europe, around 60-70€) but I am having hard times recommending it. Despite a natural and very strong midrange, it lacks bass impact, and would sound too thin and edgy for a lot of people. The K612 is a better buy, with more balanced sound and much better bass – but still quite bright.
On top of that, it requires capable amplification. Alternative ear pads, like K601 or K701 pads, apparently help the tonal balance by adding a bit more body in the bass and lower-mids.
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