Out of the box the MM 50s are an unremarkable looking set of headphones, as most in-ear 'phones tend to be. They feature an asymmetrical cable design with 1m and 1.3m length cabling, in-ear headphones with rubber tips and a small receive-call button and microphone located at the position where the cable separates for each ear, sitting on your shoulder just below your chin.
Sennheiser bundles three sizes of rubber ear-buds with the MM 50; small, medium and large. As with most in-ear headphones the MM 50s take a bit of wearing to get used to, and we don't feel the headphones are comfortable enough to wear for more than a few hours. They are very lightweight though, making them perfect for wearing to the gym, if you don't mind the small microphone bobbing about as you jog or cycle.
With the assistance of the rubber ear tip, the MM 50s offer what Sennheiser describes as "noise blocking". While this isn't complete noise cancellation it does make things sufficiently quiet to block out the jabbering of the various "friendly" strangers you tend to encounter on public transport, or dare we say, at the office.
Sennheiser knows its business, especially if you intend to entice people to spend extra money on headphones to replace the ones that were bundled with a phone or music player at no extra cost. The MM 50 is substantially better; expressing a quality of sound far superior to the comparatively shoddy ear buds that come in the box with Apple's iPhone and iPod range, and headphones that come bundled with all music playing hardware for that matter.
The most significant difference is the MM 50's extraordinary bass reproduction. Unplug the iPhone headphones and plug in the MM 50s and you'll hear it immediately. The tone is warm and rich, though it leans towards the low end frequencies, delivering deep bass and hard-hitting mids while sacrificing the treble slightly. Most people won't mind this sacrifice, especially people who tend towards bass-thumping dance tracks or ear-bleeding metal, and we found this attention to the low end helped make the audio during calls clearer.
We also discovered that the MM 50 isn't compatible with all the major mobile phone brands, specifically Nokia handsets featuring 3.5mm headphone jacks. During our tests we connected the MM 50 to the Nokia N95 8GB and N82 and both produced a loud buzz and wouldn't playback any audio. We successfully tested the 'phones with the Sony Ericsson W380, via an adapter, and the iPhone 3G. Both produced an excellent sound whether we listened to music or during calls. In fairness Sennheiser is only promising compatibility with the iPhone, though this does seem remarkably short-sighted.
For the RRP of $99.95, the Sennheiser MM 50 headphones make an excellent and affordable replacement for the underwhelming Apple bundled ear buds. If you plan to use the MM 50 with another brand of phone, be sure to take your phone into the store with you when you buy them, or keep the receipt in a safe place in case you have any difficulties.