We used the HD 205 II headphones in conjunction with a Toshiba Qosmio X505-Q880 laptop (with 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 32-ohm impedance level, it takes little power to drive these headphones, so they're easy on the batteries in portable devices.
As far as sound goes, the bottom ends aren't as detailed as those of the 7-year-old HD 212 Pro, but the HD 205 II is accentuated, and is much better than the Shure SRH440 Professional Studio Headphones, which had insufficient bass. The high frequencies are dialed back a bit on the HD 205 II, but the tops and bottoms are more in balance than the 212's. The bass is rock solid, tight, and surprisingly deep without being too aggressive--more than enough to keep the head bouncing.
The mids are noticeably recessed in the overall mix. The uppermost treble range remains reasonably well-controlled, managing to avoid the deadly sin of edgy harshness. This is important when using portable digital audio sources that may tend toward a brittle sound in the higher frequencies.
The highs on Major Lazer's "Guns Don't Kill People...Lazers Do" album sounded crisp and clean, while the lows were subtle yet smooth on Marvin Gaye's "Midnight Love" album. The overall soundstage for a variety of genres ranged from great to just OK. Most electronic music and instrumentals failed to achieve the transcendent significance intended by the DJ or artist, while big band struggled to create that toe-tapping feel. Dub-step and hard rock sounded somewhat muddled and not as powerful on the downbeats.
The HD 205 II's bass levels came across dynamic and powerful when we tried watching "Inception"--one explosion after the next had noticeable impact and shattered glass was loud and clear. Still, precision and clarity seemed to weave in and out--the sound of a gun being cocked or Cobb's totem spinning was crisp, but crowd murmurs and some background noise, such as traffic, were a bit lackluster.
Adjusting the equalizer settings on your device or adding a headphone amplifier increases the performance and overall clarity, but don't expect miracles, as the Sennheiser HD 205 II DJ Headphones are budget cans, after all. To expect professional-grade sound would be asking too much, but they do perform well for everyday casual listening and for DJs in training.