Koss sound is warm, round and turned very low frequencies, which suits me well for music Rock, Pop or Jazz-Soft, but not necessarily please everyone.
The idea that one has of a sound is very subjective, so it is better to try before purchase. The brother of a friend works at Sennheiser in Germany and lent me a PXC 250 (the high end of nomad helmets with ambient noise reduction) to test: I found the dry sound, even aggressive in comparison PortaPro . The overall balance is certainly better but the rest PortaPro more enjoyable listening. The essential difference is the isolation room: The PXC excels with the "Noise Reduction", the PortaPro do nothing and isolated acts of small enclosure at high volume.
In terms of construction, is a hoop PortaPro helmet. It is very light to carry, more than the PXC 250, but not padded foam earpieces are quite harsh. The arch does not tear my hair and adapts very well to the head. The cable is a standard length, gold-plated plug. After two years of use, the cables tend to stiffen, which for now does not affect its use.
Overall I am very satisfied with this product and recommend it.
Edit July 2014: The cables are permanently stiffened and contacts snapped. My helmet is no longer usable in the state. AKG K450 replaced with a detachable cable. Too bad my Koss sounds better ....
