Thanks for the info and links. Enjoyed the Altec enclosure brochure. I used to have one on nice textured heavy white paper, last seen with rusty staples. It's a nice piece of history with some classic enclosure designs. It reminded me a lot of information in a book: loudspeaker enclosure Design by Alexis Badmeif (sp?)whom I think was with Altec. The design advice for BR's was to maximize the radiation resistance of the driver - enclosure combination by choosing the box volume resulting in a vent area that was the same as the drivers piston when tuned to the drivers Fs.

I found some info on the Lansing Heritage site:

A 1971 Home audio brochure describes the 406 as a 10-inch, cast frame, 3-inch VC, 50 w program, 9 lb 7 oz alnico magnet structure (same as the 414), 28 Hz Fs, 8 ohms and bandwidth of 25 - 4500 Hz. The same brochure shows the 406 was used in the Bolero, a 2 cf passive radiator system, and in the Madera, a 1.9 cf sealed box. These models were replaced by 1974, and the 406 was dropped/discontinued. It was produced for about 6 years. It was only used in the mid-priced home speakers (a lot were sold so many 406's are around). They were not a part of the classic Altec theater speaker product line and seem to be poorly known. The 406B was listed in the 1970 Allied catalog for $56, the 414B for $58, and the 416A for $62.

I am still screening candidate drivers , so I have none to measure for T/S or sensitivity. My post on the High Efficiency Speaker Asylum did net a reply stating that the sensitivity was about 93 db/w/m. Strangely, the post was there this morning but had vanished by mid afternoon when I checked again. If the sensitivity estimate (93db/w/m) is correct, the 406 is a little lower than I want to go. I may try the 414.

Are any of the Eminence 10 or 12 inch drivers worth considering? I sure don't need multi-hundred watt power handling for use in my home with a 45 SET. Just need good efficiency, decent response to a few kHz, and favorable T/S parameters.

Regards,

Bob