Petro - I've enjoyed watching your progress on your speaker system. Do you have any means for measuring the frequency response of the speakers as they now stand? I'm by no means the expert here, and I'll look forward to seeing what others have to say on this idea, but I'll bet you are encountering the typically accentuated frequency response of an un-equalized compression driver in the upper midranges when you refer to the higher-volume "harshness."

Have you followed BillWojo's post about using the Altec 30904 EQ/attenuator? (30904 attenuator works!) This little crossover addition brings those frequencies down (about 6dB, if memory serves) and smooths that harshness you are referring to. It's a cheap and easy addition to your crossover and certainly worth the try.

I intend to use the 30904 on my upcoming build (A7 components). If that sends me in the right direction, I'll be using some of the on line calculators to add more/less attenuation to smooth that horn response in the normally-hot upper midrange frequencies.

GeeDeeEmm