I have a pair of vintage Hartsfields with 150-4C Bass driver and 375 driver with H-5039 exponential horn and Koustical Lens and N-500H dividing network. This is in a early large folded horn enclosure, not the classic Hartsfield. To improve the top end I would like to install a pair of tweeter's. Any idea's which would be best? 075's? 077's? 2405's or ?? What cross over would be best and at what point?