The New Folded Corner Bass Horns and the New Straight Midrange Horns now have a pair of Eminence APT-150 Super Tweeters. This is a bi-amped system with line-level RC low-pass filters for the bass and RC high-pass filters for the midrange/tweeter. The midrange and tweeter horns are powered by a Lepai LP-2020A+ amplifier and the folded corner bass horns by a Pioneer SX1280 receiver. Here are Chester and Lester playing "It's Been A Long Long Time". The preamplifier is an NAD 3020 Integrated Amplifier with "Y" RCA connectors in the pre-amp outputs.
The audio recording was made using the Tape App running on an iPad Air controlling an iTrack Dock with the high quality Focusrite preamps built in and a matched pair of Behringer C-2 condenser microphones.
Watching the FFT of this system's response to a white noise track, I find that the smoothness of response vs frequency between 300Hz and 400Hz is improved without the line level low pass filters. It appears as if the bass horn and woofer together function as a low pass filter. The high pass filters provide some protection for the midrange and tweeter combination from low frequency energy and do not appear to have a significant effect on the smoothness of response around crossover.