Don't want to go down the road of choked port design, so optimised cab volume and port for the best compromise I could RE bass response to volume whilst trying to keep bass nicely balanced.
After various cab designs were tried, I settled on the one shown on the prototype photos below. Sloped front baffle is for time alignment purposes, although how much difference this makes in practice is questionable as relative phase is usually where I try and optimise crossovers. In this case, I've used 12dB/Octave slopes in my usual approach of flattening impedance on the woofer, partly to try and compensate for quite a lift in acoustic response between 1 and 2KHz and partly so I know more precisely where I am with impedance!
It's a far cry from a "cook-book" design requiring roll-off of the woofer a little earlier (that rising impedance) and playing around with values until the deepest notch was found before reversing tweeter polarity for a nice flat acoustic response. (LR2)
This tweeter has a relatively high power handling and a commendably low Fs, so a low crossover point was possible helping with off axis performance and to limit any mid woofer beaming. Bass response is really quite astonishing for a cabinet and driver of this size. Port tuning has been kept low enough to limit driver excursion above resonance.
Resultant sound is very clean and balanced. It sounds more like a floor stander of three times the size! Overall quite happy with the end result.
I'll add more photos once I've completed the veneering and grille covers (magnetically attached). I'll be building another pair in a nice Curly maple finish as a demo pair.
Crossover values for the tweeters were altered to raise impedance, as with traditional L-pad values, impedance was too low for most amps to cope, so I've raised it to a flat-ish nominal 6 Ohm load across the board.
The Illuminator is really quite a good tweeter. I had toyed with the idea of the SB Acoustics Satori tweeter too and may still try that one at some stage as it has a very nice smooth response. Probably not up to the standard of the Illuminator tweeter though.
With drivers in place (mocked up)
Prototype crossovers (made up of what I have in the parts bin. Final versions require a lower DCR LF inductor and some tidying up):
. These are speakers I've designed and built and they will feature in my RFC line up, as in "made to order."