The American Speaker Project, now and then...

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.
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.

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)...
 
One of the future experiments on my bucket list will be to power up some high voltage field coil Jensen 12's, with a low power DC at around 30 V – – I expect to get quite good sound from them so they will be underdamped…

As I've just picked up some field coil Jensen 12's (marked C12 on the frame) that were pulled from a Capehart console (not by me), I'm curious about this experiment. What would you expect the sonic results would be if running them at a lower voltage?
 
As I've just picked up some field coil Jensen 12's (marked C12 on the frame) that were pulled from a Capehart console (not by me), I'm curious about this experiment. What would you expect the sonic results would be if running them at a lower voltage?
Great question! My 2 cents?
Well, in general the effects of a weaker magnet (ie the lower voltage experiment) are pretty well known ... lots to read on that topic for sure... it's been assumed that the magnet should always be as strong as possible -- but that's not the whole story, especially if you are talking woofers.
Lower voltage on a FC, expected results would be less sensitivity (lower volume per milliwatt), and also -- more importantly a large shift on the speaker's magnetic dampening -- this in turn drastically changes to the mechanical performance -- what's now used these days and since the 60s or70s... T/S parameters can define this.
Now, most audiophiles would drop off here .. thinking a weaker magnet would have to be automatically worse ... not always so -- the T/S parameters need to be matched up (as well as possible, I am a frequent offender especially when experimenting)...to the type of enclosure or baffle you are using.... the rest of the T/S is based all around the suspension and the paper cone , and this is where it gets interesting...

On these old Rola's and Jensen's ... the paper was pretty rigid, and the suspension almost too stiff, the efficiency really high, and lots of lower midrange -- thanks to the often phenolic wafer (or thin paper) "spyder" that holds the voice coil in center... for a woofer that can be too stiff, which equals too "fast".... so weaking the magnet will relax the mechanical spring portion of the speakers action (possibly) giving more excursion and "tubbier" bass. Later woofers went to a cambric fabric, more friendly to excursion.

A loose cone with more excursion was what Altec was after, when they changed the cone of the 803, 515, 414 and 416 series woofers... It depends on the baffle, type of music, the overall sound of the speaker (just because a FC woofer is old, does not make it automatically good), VC suspension type, and voltage level.

Your 100-180volt Jensen speakers will actually energize with a tiny amount juice, even from say, a 9 volt battery! The volume level will increase sort of logarithmically to about 40 volts, and will increase only slightly in apparent loudness from there (if memory serves) -- the rest is just beefing up the magnet's ability to control the cone -- which is a big deal, but not the be-all-end-all of SQ.
 
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Audionut

Next Round Is On Me
I have a question @hifitown ; I have a set of 416-16Z’s (black variety re-coned and recharged by GPA) that I’ll be using for a set of replica iconics, but I also stumbled upon a set of green 16ohm 803B’s recently (the original owner noted they were re-coned by Altec before they went under). In your opinion is one better than the other for the iconic project?
Pictures of the 803B’s below, the 416’s look brand new (less doping on the web) so no pics posted. Thanks in advance!
 

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