The K501 was AKG’s flagship in the late 90s, and was the last high-end model developed by the Austrian company before Harman bought it (in 94).
The K501 sounds close to the K401 and K400 (and probably K500) : this K4xx/K5xx line is very different compared to modern K6xx/K7xx models.
The K501 is certainly one of the best looking headphones I have put on my head – very classy style with a 90s look . It requires good amplification.
○ Release : 1996
○ Current status : Discontinued
○ Type : Over-ear / Open-back
○ Measured weight : 260g
○ Impedance : 120 Ohms
○ Sensitivity : ~89dB/mW
○ Average used price : $100-150
The K501 is a bright headphone, no doubt. Definitely lean sounding, with peaky treble.
Bass is too thin, sub-bass impossible to hear. Midrange is where the K501 and its brothers shine. Though absolutely forward and too shouty for most people, it renders most instruments quite well, same for vocals.
Unfortunately, treble is an issue ; there is a nasty lower-treble peak (around 6-7 khz) I don’t like. The overall low and mid-treble is forward, with average sparkle and “air” above 10 khz.
The K501 has a very wide soundstage ; in my opinion, very close to the K701 but more coherent. The K701 suffers from lack of central imaging ; the K501 does not have that issue.
It’s a very open sounding headphone, more than most modern midfi headphones (except the AKGs). The HD600 sounds narrow next to the K501 (and super-warm, almost bass-heavy).
I like the K501 for carefully selected songs, and for classical, but not so much for other genres. The tonal balance is a bit too thin and edgy. I prefer the K400/K401 : they sounds a bit “slower” and less detailed but have more body and less aggressive treble. K601/K701 pads are also apparently recommended for these vintage AKGs.
Measurements & Resources
Bass rolls off like a cliff below 100hz. Midrange is boosted between 800 and ~3khz. The treble is simply too elevated from 6 to 10khz.