"A solid pair in its category"3.5 starson by Yavrey
Pros: Meticulously built, light, excellent midrange
Cons: Seem a little fragile, lack of sound liveliness with some material
Summary: Auditioned AKG's K601 together with beyerdynamic's DT880 in an audio shop, searching for a replacement to my old, disintegrating Koss phones. Played 3 CDs of mine: Tom Waits' Blood Money, Einstuerzende Neubauten's Strategies Against Architecture II, and Queen's Day in Races; phones were plugged directly to the shop's demo Maranz CD player.
The general impression is that of a high quality product. Noteworthy is the impeccable craftsmanship of the phones. On the other hand, K601 feel a little fragile when compared to a more rugged DT 880. Also, unlike the flagship K701, K601 come in a standard, cheap plastic packaging, which, sadly, detracts from the fine build quality.
The reproduction quality was overall good with all three CDs, best with the Day in Races and worst on the Strategies Against Architecture. The phones have an impressive midrange, making May's lush guitar sound majestically full. Yet, I noticed that the phones somewhat lacked life with all the rumbling, clashing, and screeching of Einstuerzende Neubauten. These were reproduced in a slightly dull, lifeless fashion, as if the sound was coming through a veil. The effect may be attributable to me not using an amp, though --- 120 Ohms can be hard to drive.
Summing up: K601 are solid quality full size phones; I think these phones are especially well suited for listening to 'non-aggressive' material, like light rock, acoustic guitar, and some classical recordings. At the same time, I hold some reservation as to their potential performance when used with home theater systems, especially if your favorite are action, SFX-packed movies.