history: all original 1966 416A (16 Ohm), 802D (16 Ohm), 511B, N500-E component sets have been installed in my 828 MDF cabinets after repairing 500Hz XOs that had failed caps. Installed Russian MBGO PIO surplus caps for shunt and HF positions- other XO parts original in tar (see picture). I also improved and recessed the flimsy XO/binding post panel area (see picture). Running with 8 watt monoblock amps with Psvane 300B tubes. I'm very impressed by the sound of the horns (bug screens removed)- I think the Russian caps are opening my eyes to capacitor upgrade possibilities. The 416As are weak and one has a scuffing voice coil. I removed the gobs of surround glue at bottom per forum advice (thanks!) Accidently made small holes while removing. The HF attenuators are turned almost all the way down and woofs still lagging. Obviously something has to be done here.

Woofer options:
1) send 416As to GPA for stock rebuild and regauss
2) send to GPA for install of 8 Ohm cone/voice coil assy rebuild and regauss. And convert 802D to 8 Ohms diaphram myself to make an 8 Ohm set if this is not expensive. My initial thought is that there is more info, parts, and knowledge about 8 Ohm setups because they are the majority- and this might be an advantage. Downside: will no longer be "original".
3) replace a cone/voice coil assy myself and have Alnico regaussed locally- unfortunately, shipping is a pain and major cost for all of us. The magnet (see picture) is pretty small- and even looks like it could be taken apart to be gaussed (?).

Magnet question:
I took the back cover off the 416A woofs and when I placed a screw on the side of the magnet (see picture), it barely could hang on- and when touched, it would fall off. Very little magnetic force on back of magnets also. I seem to remember that the Ferrirte magnets on my 604-8Ks could pull the fillings out of my teeth if they had iron in them. I then placed the same screw on the side of my just reconed and regaussed Altec 604-8Hs (work by GPA), and to my suprise, there was also very little magnetic force on the side of the magnet. Do Alnico and ferrites exihibit different characteristics like this? I don't know what's going on here.

My impressions:
1) I think it's true that using these in a small room (see picture) is NOT a problem at all from sound quality point of view.
2) As mentioned above, horns sound great- some of the best treble I've heard ever I think. Chet Baker's "Almost Like Falling in Love": wow!
3) Despite reasons given for superiority of MDF, my gut says plywood is better. The previous owner had put a rough piece of 3/4" ply panel on the ports to get a 3 1/2" port opening. I decided to "clean things up" and make a more original look with a 5/8" MDF panel with T-nut mounting. When thumping on the panel with my fist, the MDF cab was buzzy- when thumping with the 3/4" ply panel in place, the resonant frequency of the cabinet structure itself went up (tighter), and the buzzing was way less. This removable port panel can contribute to the overall rigity of the cab significantly I think- and I will be making new better looking panels of different sizes out of 3/4" ply.
4) I am excited about moving foreward and hearing these guys with proper woofers and different crossovers. Consensus is that I should go to 800 Hz XOs, and I have diagrams from Bill for stock Altec 800 Hz XOs. Or, at some point, I will probably build XOs based on design advice I get in these forums. I'm gonna stay at 500 Hz for now (I think) so I can hear what these sound like at 500 Hz with properly running woofers before I move foreward. Needs bracing- If/when I get ambitious, I will make a a front-to-rear brace attaching top of front panel and bottom of motor board to rear cabinet panel, 3/4" plywood. Really difficult to go around drilling holes in these original boxes though- have to figure out least invasive way.

Links to Dropbox pictures:

Dropbox - repaired XO 2988-Edit.jpg
Dropbox - modified XO mounting 2990.jpg
Dropbox - weak Alnico magnet 3010.jpg
Dropbox - A7s in my home 3016.jpg