There is a "trick" to know about the K240 current models (not super sextet vintage). It wasn't designed for sonic-accuracy, but has more to do with ear-protection and desensitization as a general purpose monitor (not final mixer or anything like that).
Aside from frequency response characteristics, there is a weird timing (group delay difference possibly - dunno) purposely added to "chop off the leading edge of high-energy spikes", and also etch or dither the high end to enable long term monitoring. That is, so you don't end up in the desensitize and turn up the volume loop over and over.
So, things like gunshots, and especially metallic strikes are toned down and dithered. Or somebody plugging in a hot guitar into the board slowly and your cans are on. Stuff like that.
For rock music, you'll notice if you listen carefully, the initial "strike" of a cymbal is muted or gone. All you hear is the cymbal "ring". And that ring is dithered so all cymbals sound the same. Strikes on the drums themselves are also muted. Funny to watch and listen. Everybody seems like a jazz musician using brushes.
Classical - you'll never hear the initial strike of the triangle. Only a weak muted ring being struck by a child's energy. Again, most cymbals all sound the same dithered.
Test track: Try listening to Procul-Harem's "Whiskey Train" at a rocking (but not dangerous) level, where they are striking what seems to be cowbells and glass bottles. If you aren't listening with K240's, chances are you won't make it to the end, or if you do, be unable to hold a conversation afterwards.
So I believe this timing trick to mute the leading edge of strikes, along with dithering, is what allows the unit to be worn for seriously long periods of time. But that doesn't make for good advertising - we're protecting your ears.
So not my daily drivers, but I do use them occasionally for an entertainment factor, to hunt down little things I might miss with more accurate cans!