Quote Originally Posted by gibber View Post
That two-port 28Hz tuning you like less is very similar to the 30Hz i have here. Instead of changes on the ports my cabs have, i just tried using a beefy transistor amp and gave it a 10ohm resistor in series to my (early version) K145's ca 9ohm coil dc resistance. New Qes' equals (Rg + Re) / Re * Qes, so Qes goes up to 0.52 or so and hence new Qts is around .49 (see Qms in tables earlier in this thread).
Result is a more "normal" bass sound, the mid is similar as before, and subjective speed is slightly less, imho not too much so to offset advantages in the deeper register. Mid output subjectively is down by 2dB (should be 3 dB but the higher Qts with series-R maybe reinstates some of the premature-but-gradual rolloff that a driver of Qts=0.23 w/o series-R has).
Possibly another work around is to explore DB Keele 6th order paper on his web page and run the numbers.

My estimate is that depending on the QTS' (between 0.26/0.29 with some Rx from crossover L) an F3 in the high 30's is possible. Add a modest room gain and you are in business.

I consider adding significant Rx un suitable as you trade un warranted losses in driver efficiencies for extension when electrical boost of 6 db and Q equal 2 with Keeles formulae can offer extension in a WaF friendly box.