If it isn't designed into the drivers/horns you can adjust other ways. An equalizer could take care of a 6 db spike quite nicely. They've got nice little 30 band models now that should let you play with "spots" to your hearts content. Just make sure the bands you want to adjust are covered by the equalizer before buying.

It sounds like you're not completely sold on the "zip cord" (whatever that is). High resolution and extended HF is a good thing.

It sounds like you've put a lot of work into your speakers. I hope they're great other than the little bit of tweaking they need.

Grant.