I owned and them. Great mid range and imaging that a single driver can give but that's about it. The 166's with the whizzer cones hurt my ears. I had better results with the 165 drivers in near field. I couldn't get any lower than 50 Hz out of them and it was way down dB. I wasn't running tweeters with them and they rolled pretty heavily after 9 or 10k Hz (memory slipping). Replaced them with Altec Model 19's and haven't looked back. As a note, the cabs are not as easy to glue together as they may seems. If you don't have plenty of extra clamps, you may want to consider having a carpenter glue them up for you.
The experience with them has inspired me to try a higher quailty single driver full range or even a two way OB set up with active crossovers, someday.... Good luck and enjoy!
Back when a Foreplay 2 was $149 and Paramours had just come out the Fostex 104E was enthusiastically endorsed here and elsewhere as a great value in the Fostex recommended enclosure. I built it and thought, like Johnson, that the mid-range was superb, the imaging other-worldly but the treble made it overall sound like an AM radio.
I know that newer 6" and 8" Fostex drivers sound quite a bit better and have heard Bob Brine's speakers, with BSC crossovers, sound very good. In addition, the Fostex cabinets are far easier to build than they look, even to a Tyro. I came up with a construction method that others have found easy to use for their labyrinth horn projects.
First, forget about how many pieces there are to cut; they're all the exact same width. One rip fence setting does them all. In fact, you MUST cut them all in one session or somehow not let the fence move in between cuttings so that they're all exactly the same width. Once you rip all your plywood a chop saw with a stop makes quick work of each set of the various sizes.
After I cut all the pieces to size I placed them on one cabinet side piece and traced the positions with a soft lead pencil. Then I shot beads of construction adhesive from a tube, Liquid Nails, PL400, whatever, inside the lines , took a piece of plywood larger than the actual side piece, laid it on top and weighted it with 2 -25 lb. bags of lead shot. After an hour, with the glue sufficiently set up so the pieces wouldn't move, I shot beads of glue on the tops of the baffle pieces, laid the remaining side on top and weighted that. Finally, I nailed #4 finish nails, just a few, around the perimeter, countersunk them, then flipped the cabinet over and nailed that side. This last probably wasn't necessary but made me feel better ;-} I also glued on thin strips of Mahogany to cover the exposed plys.
This will of course work equally well with the Madisound Flat Packs. Also, before there were Home Depots and Lowes every neighborhood had a lumber yard and many still do. Provide one with a cut list from the Fostex plans and for a fee, they'll cut your plywood to size and sell you the glue and nails. Then it's off to the Hunting Supply for Lead Shot.