Treble sparkle is usually a lack of control. So, basically you're asking AKG to give it ****tier treble?
 
The K712 is AKG's attempt at listening to their consumers more, they were asked for more bass than the K701 so they gave it more bass. That's all they did. The drivers are the same, they just altered the enclosure a bit. Bump up the bass and you'll have more recessed everything else, that's how frequency response works.

Actually, you are exactly wrong.
The drivers are not the same.
But dont worry about that, just keep talking.
And regarding "frequency" response, i wont bore you with facts, i'll just let you believe that you know what you think.