Really have to agree with your post! Those assessments meet with all the experience over the years of handling these things. The simulation noted above more-or-less agrees with the times we listened to these systems. They often came in from Studios or as Cinema side fill.I own a pair of the 414-8C. They are as I believe you described: they have a one-piece cast return pot that has a stepped shape. This pot is painted a textured black along with the rest of the frame. The frame is the square edge cast frame. Magnets are alnico. The 414-8B only mounts from the front.
When compared side by side with a 414A, the cone appears to be slightly more coarsely textured and perhaps slightly heavier. Altec rated them 3dB less than the 414A. I’ve seen factory response curves for both drivers. The 414A has a classic rising response and more smoothly extended top end. The midrange response is a a bit greater than the mid bass. The 414-8B response is flatter but does not roll off as smoothly nor as high. It appears the later driver response is knocked down in the midrange a bit to better match the mid bass.
In another thread, a user simulated the Altec 614 and 9498 enclosure response. He noted the 614, with its 2” x 7” x 3/4” simple port showed a “pleasant” bass hump around 55hz that seemed to work well with the response of the 414A. The later 9849 cabinet of the same dimensions had two tuned ports of 3” x 6”. These ports were of the same area of the 614 port, but 6” deep rather than 3/4” deep. The resulting response was much flatter than the 614, with extended but not exaggerated bass. This response would seem to work well with the 414-8B, extending bass response without the mid bass emphasis. The response looks a lot more like a sealed box than a vented enclosure. I think the response was tailored for near-boundary location in smaller control rooms.
The early 414's (A and Z types) are more valuable, as they are sought after both for the midrange response, which can add detail -- that and the better efficiency for our favorite -- low power SE amp crowd.
Altec was definitely making tweaks for flatter response and for extended bass (the heavier paper and broader accordian edges)- which in sealed or heavily ported arrangements, after all was said and done (ie non optimal crossovers, thick spandex grille fabric etc) -- let to overall lower detail, sensitivity and somewhat muddier sound. Many of these things were simply beyond their control, and the designs were really in sync with the desired sound of the era, and the use of brite and harsh silicon solid state amps...
None of this means you can't do a very nice system around the later Alnico (step backs) or even pancake ceramics... quite the contrary - I would say -- you just have to be cognizant of the lower sensitivity --- which is really no problem still for most tube amps in normally sized rooms... Given the right T/S workups / considerations -- these flubby movers can even be pressed into service in Open or Pseudo open baffle... I have been seeing 15" and 18" sizes, similar to the open baffle woofer a customer was looking into over there at aesspeakers.com
They make a "loosy goosey" woofer designed for open baffle. While the Altec's were not designed for it -- I have seen it done and have heard feedback of positive results -- sometimes you just have to try it! (With woofers, of course allot depends on the amp).
Given the cost of the over-sought-after 414Z's I do encourage customers to experiment, especially with Jensens and other heavy paper classics... Of the early Altec 12"s the 414Z is one of my lesser fav's as the reddish cambric treated edges tend to (sometimes, just the unlucky) get hard, and accentuate the midrange favoring properties above (in this case they are both less efficient and a bit thin)...