Putting a JBL 2226 or an Eminence Kilomax 15 or Omega 15 in a Theater Series four π cabinet results in an EBS alignment having a -10dB shelf. It produces an interesting response curve with high 90Hz f3 but low 20Hz f10. Basically everything below 100Hz is shelved down -10dB, but then you get output all the way down to 20Hz.

It's an interesting response curve and potentially useful. But when used as the midwoofer in a two-way speaker, I prefer the JBL 2226, Kilomax 15 and Omega 15 speakers to have a different alignment.

There's another hybrid option that works well though. Move the Helmholtz frequency up to 35Hz or 40Hz. This moves cutoff up from 20Hz to 35Hz, but it also brings the bass shelf way up to the -3dB line. If you take a Theater four π cabinet and cut the port out, enlarge the hole to 5" diameter and remove the duct, you've formed this kind of system. Response is down -3dB at 100Hz, but it remains flat from there down to 35Hz. To me, this is an attractive modification of Theater four π cabinets when used with JBL 2226, Kilomax 15 or Omega 15 woofers.