We listened to the HD 201s with a Toshiba Qosmio X505-Q880 laptop (includes Dolby Home Theater technology), an Onkyo TX-L5 receiver, and the Apple iPod Classic, Creative Zen: Vision M, and Zune HD MP3 players. With a 24-ohm impedance level, it takes little power to drive these headphones, so they're easy on the batteries in portable devices but require a lot of current (i.e. a strong headphone jack or an amp) to sound best, especially when it comes to the bass.
In our audio test, we compared the HD 201 with a favorite in our budget category, the Koss. In contrast, the bass is clean and even with the rest of the soundstage but still lacks the power and oomph of the PortaPros, though good amplification helps a bit in that regard. If you're partial to Sennheiser and want to stay under a $100, the provide better bass, but they'll cost you three to four times as much as the HD 201s and less than twice as much as the PortaPros.
The midrange avoids any serious resonance and sounds natural, though there are a few mild peaks to the sound that do little to offend the ears, but the guitars tend to sound either too bright or get lost completely in the mix. Vocals are also on an uneven scale; some notes are slightly overstated on some songs, yet understated in others.
The highs put a slight emphasis on sibilance, or words that include an s sound with a harsh hiss that can be annoying at times, but isn't a major problem. Extension and detail are pretty decent, and the soundstage is typical of closed-back headphones, although slightly better than what one would expect for the price.
For a closed headphone, the HD 201s don't shield against ambient noise very well. They're adequate for blocking out sounds in the home, but disappointing for most portable use. The HD 201s also exhibit very low sensitivity, so it takes cranking up the volume to the max to bring them to satisfactory or normal loudness levels. This may not present a problem for home theater listeners, but MP3 players with volume limits can be frustrating to use if you enjoy listening to music at a very high volume level. Noise leakage is nonexistent on MP3 players and at a minimum on AV receivers, allowing you to remain a closet Beiber fan.
The Sennheiser HD 201 headphones aren't the most revolutionary cans ever created, but their price and tonal balance make them a boon for the casual listener. They may sound underwhelming compared with boomier headphones with multiple drivers, but they still deserve high marks for achieving a cleaner overall sound at such a low price, not to mention their comfortable fit for extended listening sessions. We recommend these headphones if you have an amp or like to listen at home. Otherwise, you may want look into something that is more commuter-friendly.