The JBL model that uses a woofer above and below the midrange horn is the K2, not the Everest. Information about it is available at:

http://www.audioheritage.org/html/profiles/jbl/k2.htm

It was built prior to D'appolito naming this configuration and describing its benefits.

The D'appolito configuration uses a woofer above and below the midrange/tweeter. It uses geometry to partly solve crossover, efficiency, and maximum output issues. Mr. D'appolito has published his designs in the Audio Amateur (now AudioXpress) and theory papers in the Journal of the Audio Engineering Society.

Brian