Did you try the attenuators? LOL! I don't think most people would share this view, BTW. Most people seem to echo the OP ... slowish bass (and not deep enough), maybe due to 2 x 12" woofers per side? I suspect the Carmels might be better with one 12" per side and the 1" CD padded down (even more)? IDK ... then you'd have an "Avalon." Would be easy to try at any rate.
To the OP: I haven't "tweaked" mine in the typical sense (i.e., maintaining and improving what's there) ... rather, I've treated them as a platform on which to experiment (different drivers), expand (additional drivers), different crossovers altogether, pulling horns out, etc. Loads of DIY Altec systems for your viewing pleasure around the 'net using 414 or 416, 802 or 804 or 806, and 3000 or similar. This one is quite typical (probably because it is much copied):
http://members.myactv.net/~je2a3/speakers2.htm I guess what I'm trying to say (instead of answering your direct question -- sorry) is that I wasn't as interested in improving my Carmels per se as I was in building a great speaker system. There have been times when my Carmels were very far from stock ... although they're pretty close to being back there now ... and about to change again(!)
You can find some (but admittedly not tons) of info on the Carmel by googling 838 and/or 9844 (the upside-down monitor version of the Carmel) ... and don't forget google images! You may get better results.
If it took you ages to figure out that your speakers are Carmels, then I have to assume the "Carmel" sticker is missing from the back panel.
That leads me to believe that your cabinets may not be original? Whatever the case, original cabinets should be roughly 31"W x 24"H x 16"D -- on ~5" legs, obviously.
On pricing, I figure that if a pair of 804s or 806s go for ~$400, a pair of 414s go for ~$250, and a pair of N800s go for ~$200, then you've got an ~$1100 pair of speakers(???) That's what I'd value them at, but I have definitely seen them go for +50% recently. You may well be paying a premium based on your location.
Good luck with these!