I really wanted to like these monitors; They have a lot going for them. The price per monitor is amazing, they look beautiful, and the sound quality and imaging are phenomenal. They have a very balanced frequency response, though they're definitely not for bassheads.
Unfortunately, a common issue reported by lots of owners of these monitors, and one which is allegedly acknowledged by Tannoy themselves, is the fact that these monitors emit a constant, irreparable hissing sound when switched on. It's worth mentioning at this point that the hissing does not get louder or quieter based on what volume you have your monitors set at.
How noticeable it is and whether it could be a dealbreaker for you depends on your application. I was using them for DJing in my bedroom, so the monitors were fairly close (< 4 feet) to my ears. I kept the volume fairly low in order to spare my hearing, and the hissing was always noticeable and became slightly distracting/annoying over time. If you are going to be a fair bit farther away from your monitors, or if you are certain you'll only be playing music loudly on these then the hissing will be much less noticeable to the point where I would definitely go for the purchase.
Sadly, because of this issue, the 502s weren't really doing it for me, so I've sent them back
