The headphone remote doubles as a microphone for hands-free calling on a compatible smartphone, and similar to most headphone remotes, you can also double-click the middle button to advance a track on your music player--we should also note that the two volume buttons won't work on any iPhone released before the 3GS, a symptom of Apple's hardware, not Sennheiser. We also had off-and-on success using it with an Android-powered smartphone, so your mileage may vary with non-iOS devices. If you don't own an Apple iPhone, however, you can save $20 buying the remoteless version instead, called the PX 100-II.
Having tested and owned the PX-100 headphones, we're thankful Sennheiser didn't stray too far from the original's sound quality. The sub-$100 price point seems to be the limit for what most consumers are willing to spend on aftermarket headphones, and the PX-100IIi's won't disappoint.
The headphones employ dynamic drivers and neodymium magnets to actuate the audio current and create a warm sound profile that sways heavily toward the low end. Light jazz and classical listeners may want to consider an alternative over-ear headphone, perhaps the Koss Porta Pros. The majority of listeners, but especially rock, R&B, and hip-hop fans, will find the extra bass push a welcome addition to the sonic profile, adding a sprinkling of richness to the already detailed definition.
We compared the PX 100-IIis with the Koss Porta Pros, an even cheaper over-ear headphone that began production in 1984 and have since become a favorite among audiophiles for their range and depth. We used Michael Jackson's seminal "Off the Wall" album produced by Quincy Jones as a litmus test, and the Koss PortaPro represents a more natural, brighter sound with a longer frequency range from 15,000-25,000 Hz for clearer instrument separation than that of the PX 100-IIis.