Get the hifimans, they are better than the 650's in nearly all circumstances. Wider sound stage, deeper bass, less treble roll off and overall more detailed. The 650's are better if you want a more relaxed listening session with a tube amp.
Just because the 650 has a higher price and higher model number doesn't mean it's any better. Both use the same drivers, the HD650's are a slightly tweaked HD600. It depends on what you prefer as to which is the better of the 2. The HD600 is more neutral and the 650 is a darker version of the 600.
Actually you are wrong:
HD600 Driver part No. 091570
HD650 Driver part No. 092855
Key word there is "older"... Not pertinent to the 400is. They're also not designed as portables so their size shouldnt be held as a con...
so if someone is looking for a smartphone and someone suggests a Note 4 size shouldn't be mentioned?
I doubt I'd be able to put a Note 4 into some pockets meaning that size does indeed matter, it effects how easily you can move about with them on, how comfortable they are, etc, etc.
i never listen to music sitting perfectly still for hours at a time, i will do other things whilst listening. so size is a con if you plan on moving at all whilst using them.
They're also in a different league to the HD650s/X2s.
Now we're entering "night and day" - exaggeration territory![]()
When you post an upgrade to K550 you will unleash hell
Personally speaking I love my AKG K550s, I researched so much to find better Closed headphones then those, but found not many there are some models like the hifiman and HP 100/150s etc but they are all very similar to the AKG K550s.
Open headphones are going to be better but also leak noise quite badly, if you are the kind of person that needs to respect privacy and quiet or you watch tv and films at 3am it may not be ideal.
Ill be enjoying my K550s for a long time yet, so far can't find anything that beats it in noise isolation and performance yet and at 99 quid hard to beat, look forward to AKGs next upgrade if they ever come out![]()