But enough about design--let's get on to the sound test and that alleged musician-grade reference-quality sound that Altec says comes courtesy of a "balanced-armature" speaker. (The specs say they have a frequency response of 20Hz-20KHz, which is the standard.) Alas, the Pros just don't quite deliver on Altec's promise, but they do sound decent. They provide more clarity than the Titanium 326s and have tighter bass, but they are pretty aggressive earphones. As some might say, they're in your face--they come right at you (in other words, they're the opposite of warm and balanced). That's going to be appealing to some users, but this reviewer did experience some listening fatigue after wearing them for about 25 minutes on the subway ride in to work.
As for achieving reference-quality status, we put them up against the Etymotic Hf5s and the and the Pros were not in the same league. Granted, those other earphones cost close to $150, but that's the price point where you just start to get into musician-grade reference-quality sound.
The long and short of it is that Altec probably over-promised a bit with the Pros. However, they still offer decent bang for the buck and fit in nicely with the rest of the BackBeat line. At around $80, they're no homerun, but are a solid double.