Switching back and forth between the two while listening to CDs of Brooklyn soul group Sharon Jones and the Dap-Kings, we found the Image One and the P5 have a similar tonal balance. The P5's bass has better definition and the soundstage is more open, but the Image One sounds more dynamic and rocks harder with more treble detail, so cymbals and brass instruments appear more lifelike.
The Image One also does a better job of blocking external noise than the P5. Considering the Image One sells for about half the P5's price, we give the nod to the Image One.
Sennheiser's HD 555 ($170) sounds even more open than the P5 and is also the most comfortable of the models we've mentioned here. Comparing the Image One with the HD 555 while watching the "Lost: Season 2" TV series DVDs, we noted the Image One put the sounds of the island--the surf and jungle--more inside the head, while the HD 555 placed the sounds farther away, which sounded more natural. Sennheiser's new HD 598 is even better in that regard.
The Image One's big bass outperforms headphones that sell for double its MSRP, but the bass may feel like too much of a good thing to some buyers. Then again, some may love the abundant power. It's not just the bass, however--the Image One's richer tonal balance also covers the midrange, so voices and many instruments have a bigger and warmer sound than they do on other headphones.