Using bass reflex ports primarily for cooling for very high excursion/power drivers could be considered an improvement over the Bertha or OP's designs, but that concept has been around since that time.
TH don't have the enclosed chamber heat problems.
Pretty much.
FLH need to be larger to have as low Fc/Fb as a TH, but once you go "Huge", probably better off with a FLH design.
Rather than the classic FLH, I'd probably opt for the flexibility of DSL's "BC" type designs if inclined for huge FLH:
https://www.diyaudio.com/community/threads/danley-bc-subs-reverse-engineered.263812/page-13
Art
Old thread, but Richard Long used a custom Eminence driver in the Bertha. I did a club with him that had 4 Berthas with very rare 10 foot wide mouths - they were double stacked on top of each other - went real low………….. likely the same driver EAW used in the 882. I tried Celestion 18s and JBLs in the Levans, but they didn’t last 6 hours with Crest 8001s driving them.
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Do the coils burn? Or the cone shred to pieces?
If I'm not mistaken , FLH do not push the driver with extreme compression forces like BP6 designs, also they have a sealed chamber right? So overheating I guess, I think the custom drivers were ordered with heavy venting and split coil design to aid in the motor cooling.
Ohh so stronger motor was those custom made drivers , so I guess the
B&C 18ds115 will not break a sweat inside a Bertha, but at the time there was none close to the 18ds115