Pros: Practical for mobile use and for "lower quality" mix comparison. Replacable cable is a clear plus.
Cons: Bass and low mids too obvious, some smear, a certain tendency to mask the higher end of the freq. spectrum
Useful for fast in-between work.
Initially bought for mobile and night use with a Yamaha P120 digital stage piano.
Could have better impulse and high-end spread for the money, but the overall sound appears musical enough for extended use (in hours).
Still good enough to listen to mobile phone / mobile player audio or in-game audio for more than an hour in a row.
My personal result:
No fair comparison possible regarding any high-res earphones like K-6xx / K7xx / K8xx, or any other serious product for regular studio use by any other leading company.
Nowadays, I mostly use the beyerdynamic DT 770 Pro (250 Ohms) for all the subtle work during mixing and pre-mastering live recordings.
The K450 proves to be useful for the necessary "upper mid fidelity" comparison of pro mixes achieved by using higher quality earphones and high quality studio monitors (ADAM).
Light build, good wearability, solid craftmanship, as one might want to expect it from AKG.