I took a shot at a small modification of the BT's... As I had seen on some pictures on the internet, they have a bass port (a small hole) on the back of the driver. So I opened up the earcups and put a small piece of electrical tape over the hole and... Voila! Now I got a clear reduction of lower bass frequencies!
Now, compared to my AKG K240's which I've been A/B testing against the BT's still have their distinct sound of their own. They still sound meatier and have slightly scooped mids, but most importantly, I got rid of that thickness in the lower bass frequencies that had been annoying me and to my ears they sound much more pleasent now!
I know that everyone have their own idea of whata balanced sound is. My ears have been accustomed to my Yamaha HS50M studio monitors and K240 headphones which are rather focused on mids and highs so in comparison the BT's represent a different world.
Do you have pictures of this bass port hole? If you want to see bass heavy, take out the rubber aspiration limiter (don't think it really has a name) in the AKG K172, which is likely in the 272's as well.