The K401 was the little brother of the famous K501. Differences are minimal though ; the only premium thing the K501 has over the K401 is a genuine leather headband. Other than that, exactly the same. Same pads, housing, specs. Driver baffles are a bit different.
○ Release : 1996
○ Current status : Discontinued
○ Type : Over-ear / Open-back
○ Measured weight : 260g
○ Impedance : 120 Ohms
○ Sensitivity : ~89-90 dB/mW
○ Average used price : $50-100
The K401 has a similar tonality to the K400/K501 : very open sounding, mid-centric, with rolled-off bass and somewhat peaky treble.
Bass is very thin and terribly lacks extension below 100hz, but there’s at least 2 dB more bass and lower-mids compared to the K501, improving the balance.
Midrange is very nice – forward but in a good natural way. Although a lot of pop or metal might sound too shouty because of the excessive energy around 1-3khz.
Treble is way less peaky than the K501 or K701. Not as smooth as an HD600. Still some low-treble peak. It lacks a bit of extension past 10khz, on that point the K501 is slightly more performing, giving better sense of detail retrieval. The K401 is also a bit slow sounding.
The K401 still has a wide, open sound with decent balance despite the light bass and 1-6khz energy. Not easy to find but usually quite cheap, as most people want to obtain the K501, K240DF/Sextett or the K1000.
I would only enjoy the K401 on classical or vocal music, but no so much with other genres.