AKG K240 MKII by Jomox
I've been using one of the latest versions of the K240 Studio MKII for a little while now (55 ohm version with gold highlights) I find them to be good for reference checking and they do a pretty good job of putting mixes together also.
Overall I find their sound to be quite flat and neutral, there's no hype anywhere in the spectrum everything is just nicely balanced. Their sound is a little dull due to how flat they sound, some people very much like this, others not. But due to their laid back sort of sound with quite flat response I can use them for hours on end at quite high output levels and get no fatigue at all.
They are quite detailed overall, I can hear most flaw's in mixes, but I find it a bit hard to detect all clicking with these, these clicks are often not heard very well or at all on these, which you can clearly hear on a decent set of monitors or more detailed headphones. The sound stage and stereo imaging is excellent though.
I'd say the mid range lacks a bit detail and it's hard to use these to check for harsh mid range frequencies, this being the case across the spectrum, they are quite detail as said above but they don't present everything perfectly such as more detailed headphones do.
The build quality is overall good, they can seem a little flimsy but they are solid and they are extremely comfy to wear, you can wear them for hours, you don't get any sweat from these after long use.
After getting use to how they present things I've actually done a couple of good mixes with them, to find I only need to do minor tweaks on the monitors to fix some things.
I am only powering them by the EMU 1820m headphone amp, which is not high end, it lacks a bit of low end and overall output, though it is quite clean, but a higher end headphone amp can give a different view on these headphones.
If you want bass, mid or top heavy headphones with an aggressive sound and extreme detail these are not for you, but if you're after a set of headphones with a quite flat response, laid back sound that are very comfy and give no fatigue at all then you may well get on with the K240S MKII.
Quick edit in response to the 3rd view. It's quite confusing with the models but the qold plated version I have is a MK II Studio version. The box clearly says MKII Studio and with the gold highlighted version on the box. These are the ones made in Austria, I believe the others are made in China and are suppose to be of lesser quality. If you get the ones made in Austria you get much better build quality and I think sound also which would explain why peoples experiences with these differ as we are using different versions of them. (These have been around for years so there have been a few different updates)