The quality of cable is quite different on the two 'phones. The Sennheiser's cable is thin and leads to two very flimsy looking mini-jack connections, lacking in any supportive protective moulding. As these joints are usually the first to break it's disappointing that more care hasn't been applied to strengthening them. The Icemat's on the other hand have a reassuringly thick cable thatâ€™s less likely to become entangled with itself and is well protected at all joints. Unfortunately, we're back in piano wire territory with the microphone cable. The entanglement possibilities that a single cable presents can be infuriating, but put two together and a whole new set of physics emerges with cable confusion running into several higher dimensions.
The PC 155's feel light to wear over extended periods and the large ear cushion, make them the more comfortable option, particularly for pixie-eared people like myself. The Icemat's are noticeably bulkier and whilst they neatly adapt to your head size, the large size of the speakers and smaller sponge outer ring made them less of a pleasure for wearing.
During my research, I've read only positive reviews about the sound reproduction quality of both sets of cans. For the money they do give decent results, but are by no means exceptional. The difference between them isn't substantial but it is definitely noticeable.
Describing sound quality is inherently a personal thing but I can say that the Sennheiser's have a balanced and intimate tone that focuses on the mid range. The higher frequencies are not well represented but a bit of EQ using the sound card's mixer can help with this. Bass is reasonably produced without sounding booming: it's not a sound to get excited about but the job gets done.
The Icemat's have noticeably more treble with a roomy and spacious sound. There is a hint of boxiness to them though and despite the ears being closer to the speakers, the sound appears a little more distant.