Pros: Tons of tight bass, responds well to EQ, comfortable pads, easy to drive.
Cons: Iffy build quality, still veiled after EQ, lacks detail.
When I first put on the XB500s, I have to say, I was rather impressed by how they felt. The giant pillow pads gave a unique feeling that was far different than typical pleather pads in this price range. My main issue came when I began to actually listen to them. I did notice that the overall build quality felt a little spotty and I worried that I would break them with a relatively minor mistake. The volume was high coming even out of a portable source, so amps are unnecessary.
In their field of expertise, bass-heavy music, I felt like they did an acceptable job. The bass was incredibly overpowering, but it felt fitting. I had never had a pair of headphones produce that kind of rumble before, the sub-bass was excellent and the bass was all around very tight and well done. My main problem was that they sounded mediocre at best in genres out of their comfort zone. For much more lighter acoustic music or classical the bass shows up all over the place in areas it shouldn't and simply distorts the sound to no longer being fun to listen to. For an idea of how much bass and rumble these things bring, I can EQ down the bass 10dB and they still slam harder than some of my headphones. The mids and highs on these headphones really are not there.
That said, they do respond well to equalization. I feel like the reason they respond so well to equalization isn't some innate characteristic of the headphone driver being very adaptable as much as the headphones are already so imbalanced that balancing them out improves them all-around. The sound really clears up if the 100hz range is brought down compared to the mids and highs. Even after this improvement, however, the mids and highs still felt like they were veiled.
I feel like the XB500s could be a competitive headphone in the $30-40 range, fighting against cans like the JVC HARX700 and HTF600, but they are a bit outclassed in the $50 range for most general usage. For someone who is a total basshead and wants bass at the sacrifice of all else, I suggest the XB500s. Otherwise, I feel like many other less headphones in the price range offer a greater amount of clarity, sound quality, and build quality.