a) Which two are you referring to when you say difference is big? K7XX and K712?
b) Going from HD600 to HD650 should be significant. They have different treble characteristics.
c) This makes no sense. K701 the most balanced? What. I had the K701 from 2010.
I thought K701 was quite boring with not much bass, and elevated in the treble region.
I was just wondering if there is something with bass and sounds balanced across the spectrum (without being bright). LOL.
d) How's the K812 in comparison to the K7 series family?
a) There's a big difference between the opposite extremes of the K7-family.
That's K701 vs K7XX.
b) I've owned both HD600 and HD650. Still have the HD650 around. Although they don't sound the same, they are both tuned similarly.
HD600 is more vocal oriented, slightly drier and more midcentric overall, while HD650 gets you pretty much the same sound on slightly roomier and more laid back fashion.
But all in all both share a very similar character, which is expected as they do have a very similar design.
c) I've said
K712 is likely to be considered the most balanced of the family.
d) K812 is a perfected K701, which means fuller sound (approx +3dB for everything below 1kHz region) preserving K701's treble linearity, unlike warmer K7-variants.
It's also different in terms of presentation as it's slightly clearer and faster, leading to superior instrument separation/tracking.
Keep in mind that despite being slightly warmer, the K812 preserves the incissive, tool-like sound of K701 that can get sibilant or even strident if the recording leans towards that side.
In other words, K812 is not an easy going and relaxing headphone like the K712 can be.
High grade AKGs are known for being bright, they are all relatively bright...
K7XX is the one with more bass and likely the one that you'll find less bright. Not necessarily the most balanced, as all parts of the spectrum come into play when it comes to balance.
As I've said before, K7XX might fall into the slightly v-shaped camp, with raised bass, recessed upper mids/lowest treble (3-4kHz region) and relatively highlighted 6-8kHz region.
*Everytime I refer to K701, I refer to the current version (bumpless headband, made in china, with display box) which is likely to have updated drivers relative to early K701.
According to some sources AKG has updated the K7-family drivers more than once in its long life in the market. So your 2010 K701 might be slightly different than current 2017-2018 K701.
Same applies to K702
Can we all just agree K712 is the best? K7XX was a mistake, should have been K712.
I don't think so, because personal preferences, recordings and equippment involved play important roles here.
K7XX is more of a consumer oriented version, nicer for gaming, movies, EDM, mainstream music.
K712 is an all rounder reference headphone. Like an AKG version of HD600 and HD650 balance.
K701 and K702 are more along the lines of HD800/HD800S in terms of tuning, so they are less warm, more expansive sounding and much more picky with recordings and equippment.