This is probably the first audiophile-level speaker we have owned, and the experience for us was astonishing. Music that we had enjoyed greatly on less worthy speakers became music with mind-blowing depth and detail. That itself resulted in a range of feelings, such as the sense of being 'in' the sound, close to the person singing, or being able to mentally focus on an instrument and 'see' how it was being played as though the musician was right there. If there is anyone out there considering moving from basic consumer electronics up to something audiophile-level quality, then while these speakers may seem expensive, the pricing is really audiophile entry-level and honestly there aren't words or superlatives to express how different, how overwhelming it actually is.
However, despite all the electronics (Yamaha A-S501, Marantz CD player) being within spec and correctly wired up, and without any signs of clipping or distortion, and at around 50% of the amp's volume setting, within a few hours one speaker suddenly failed, and catastrophically. There are already a few example of this on the internet (such as this one https://www.reddit.com/r/audiophile/comments/1emxmr/ive_never_had_a_speaker_fail_like_this_now_what/)
Unfortunately, neither KEF UK nor the local distributor recognize this issue. Their conclusion was that it was externally damaged. I wish I had a video of how we all sat there watching the speakers and listening to music (granted, pretty loud), and then BOOM one speaker just gave up the ghost. I can tell you, after that outlay (which is a lot where I live) and after that ecstatic musical experience, we were really, really disappointed. It was literally shock and dismay.
Thankfully, the local distributor (and especially thanks to www.l-e.cz, whose customer service is top class and really helped us out with this) decided that they would fix the thing anyway and send it back.
If it's any use, the failure happened playing electronic music with intense sub-bass. If I had to guess, there is a rare and unusual constellation of circumstances (positioning, type of music, using subwoofer, I don't know) that result in this speaker failing in a bizarre way. I wish KEF would take this issue seriously and either revisit the design or put some kind of additional guidance in their manuals to avoid it.
Other than that rare but real problem, these speakers are phenomenal.
KEF Q350 User Review
Amazing sound but rare and unusual failure occurred within a few of hours of usageReview of KEF Q350 Hi-Fi Speaker by FrankSlater, Nov 16, 2017.This item was purchased for ~GBP 488 from www.l-e.cz in 2017. The reviewer still owns this product.
Ease of Use10
Value for Money10