It's been a very long time since I've worked with or listened to small closed-box speakers, a design approach pioneered by "East Coast Sound" proponents of the '60's - AR, Advent, KLH, etc.. Building DIY Minis recently led me to trying that approach with JBL drivers, with good result.
A little research in Dickason's Loudspeaker Design Cookbook serves as a refresher on the essentials:
1) A good starting DIY project - easy to build and easy to succeed; the alignments are not critical.
2) Excellent extended bass, as the rolloff is just 12 dB/octave.
3) Driver parameters:EBP = Fs/Qes < 504) Box size - for true air suspension, < 1/3 Vas.
Qts > .3
5) Easy to measure (test) and understand.
There's not many JBL drivers that qualify, but BB6P EBP meter identifies these potential candidates:
116A, H, H-1
Another group, more intermediate between closed and vented designs includes:
[Lists subject to change without notice.... ]
I have been using a $15 yard sale pair of AR4x as test boxes (18.45 l, 0.652 cuft gross internal volume,) but recently discovered that the OASR "Dr. Seuss" horn would just fit. Ut-oh:
3" hole saw and small Sawzall make the "clover-leaf" cutout for the OASR horn with 2407H neodymium tweeter.
708G-1 8" woofer fits perfectly. I'm trying others, too.
Control 128W crossover (2.5 kHz) plus notch filter on the woofer and L-pad + compensation cap on the tweeter gives immediately satisfying results, bottom.
Off to critical listening tests, soon....