A simple long L34 section series tuned high order QW BP. I call it LL34TP118. Quite ROAR-like, but optimized for indoor use with a much deeper response. Same mid bass peak centered around 80 Hz to accentuate drums and the "drive" in most modern music. It is easy to EQ to whatever level that suits your needs and preferences.
With two simple points of EQ and a steep 48 dB/octave low pass filter most of the roller-coaster-ride like spl response flattens out to much less then a typical room does to the spl respnse.
I am listening to Groundation (Reggae), some classic 80ies music (Sting, Bryan Ferry, Tina Turner etc) through a 12 inch version of this design as I type, and the bass is very effortless, clean, immediate and present in the room. Great reproduction of all the small quirky modulations and details that tells me that this is very far from the droning one note high Q response of a bass reflex, and that greatly increases the sense of drive, the tactile character of instruments and of the recording environment.
https://www.diyaudio.com/community/threads/tp12ll34-duality-and-positive-feedback.344958/
Original thread of my BC 12PS100 based build, with lots of measurements and comments.
Add 500 ms of much worse stuff from a typical indoor listing area, and the near field measurement response of the speaker becomes a much smaller part of the actual sound you listen to. There is a lot of secondary effects that tend to be overlooked when focusing on simple near field measurements.
In my opinion, missing the forest for the trees. One period of 20 hz is 50 msec, how many cycles does it take for the ear / brain to recognize low frequencies? As far as the 18DS115 being 'no good' for reflex enclosures, I think B&C would disagree.
You may like your 18PZB100 in 55L, but it's 50% BL point is 8mm+/- I see no point in trying to heavily EQ and put a huge power amp on it unless you are in a small room. According to Klippel, 10% distortion will appear when Bl drops to 82%, and 20% distortion at 70% Bl.
😍cant argue that until you need something MORE for any reason(goofing off or exploiting things because).... then the snowballs all drop from the top of mount everest in 8 different directions. The 'goofing off' concept still has a serious hierarchy that can represent a baseline reference that can be "compromised" from, in reverse, instead of ignoring the point of reference adn just settle for a WAF or 'size matters' or IM TOO LAZY(busy with life to be fair) to get retarded/ imature, LOL?!
But, apples to apples(apple sauce, pie, fritter, juice, cider...), no 'room', no excuses(WAF), no dsp/EQ until AFTER the diy fun/science/math/art of wood/sawdust/simulation of non garbage in/garbage out scenarios are done... there is a 'BEST' for each driver if shooting for widest BW/ greatest output within that and least hazardous junk above thats a ghost of odd harmonic issues and leaked HF standing wave material and imperfections if ignored. sealed is a HUGE compromise in one area thats important...bass extension, and youre not always MR hifi/ mr KINKY, ive seen the basshead sneak out, he likes to mess around with infrasonic designs and ?? 😀