I might be buying a pair of home made Altec VoTT and Peavey

[bowtie427ss]

Does anybody know the difference between the 418-8H II, 421-8H II and a 416-xx and why the 418/421 have a free air resonance of 35hz while the same looking 416's Fs is 24hz?

It'd be a much smaller list to list what's the same between them.

418 is a sealed motor(unvented) which probably renders it's continuous power handling a bit less than claimed. 421 is similar to the 418, and early 421's probably shared many moving parts with late 418's. In contrast to the 416, they're musical instrument/sound reinforcement drivers. They're ruggedized, heavier cones, aluminum voice coil formers, heavier damper.................... these are the general qualities. There are nit picky little variations between specific models, not really worth mentioning unless you're hard pressed to discuss gap depth, voice coil winding length, Xmax, etc etc, there are much better versed fellas here to explain all that if you need to know.

The 416 is the only one of the three mentioned that is a true "woofer" with usable extension into the lowest octave(in an appropriate enclosure, not a VOT mid bass horn). It has a lighter moving assembly and more compliant suspension than the MI/PA drivers. This comes at the cost of power handling, and abides by audio law #1 "everything is a compromise".

I am forcing these things to play low although I am only sitting three feet away at the moment and I don?t have them cranked up since the little woman is in bed.

FWIW, when the little woman is away and you want to crank things up a bit, you're quickly going to reach the excursion and/or input power limits of those 418's, and while you can probably overheat them until your house smells and the room begins to fill with smoke a few times, you'll only bottom the coil former in the gap, or extend it beyond the pole piece once.

Of course in my own warped mind i'd consider their demise a good thing as those have the stepped alnico motor of the most coveted of 416's the "8B" version, and i'd promptly have them re-coned as such, heck i'd even paint the frames the correct color for the 416 as well.

Just my .02 of course.........................

[VolvoHeretic]

Thanks BowTie. I turn down the bass at louder volumes. I will enjoy these as is for the time being, and after I get the A7s running again, work on these. I need to get some deoxit and clean up the potentiometers on the crossovers, one isn't doing anything except making scratching noises.

[bowtie427ss]

I need to get some deoxit and clean up the potentiometers on the crossovers, one isn't doing anything except making scratching noises.

You're on the right path, it should actually be an L-pad in the N501 though, most of the time they will clean up pretty good. But, every once in a while you'll find that the resistive winding and/or the wiper has become pitted and unreliable.

To expand on something i mentioned early in the thread, the N501's are really mis-applied here with the 32B horns. 500 hz is too low an XO for them IMO. Altec only ran them as low as 800 in the A8 system, 1500hz in their studio monitor(9849) application, and 1700hz in their hifi(model 15) application.

I agree with OG that the drivers are likely symbiotik loaded, i don't think aluminum phragms would still be working.

I'd wager that raising the XO point and installing aluminum phragms would probably render them a very different speaker, in a good way for hifi apps.

Again, just my .02...........................

[VolvoHeretic]

Thanks again Bowtie, I will admit that at first listen, I was disappointed, but after several hours of tweeking on the EQ and learning what these things want, I am warming up to them nicely, even with their flaws. I am trying to clean up my living room and make room for them in the corners, Wifey is chomping at the bit to get her Christmas decorating going.

[Old Guy]

That small horn likes 1200 better than 800 IMHO for xover.

Pretty much all that has been said on the differences, higher Fs drives generally have lighter voice coils assemblies. The paper dome trick will cover the overtones from the dome and drop the Fs. I have never tried removing the aluminum and venting VIA the 416 dome, would like to do it under controlled conditions, but as surviving 418's with original cones get less common seems hardly worth it. I just look for blown ones and recone as 416.

[VolvoHeretic]

Ok, I have been alone with these things for a couple of hours placed in the corners of my 14'x36' room, and have been listening to my favorites; Weather Report, Return to Forever, and Mahavishu Orchistra at maybe 40 watts, have them dialed in and loving it. I have the EQ set flat except 25Hz and 40Hz are at +12 db and no tone from the amp. I can feel the bass inside me which doesn't sound muddy in the least. Maybe they just needed to warm up? Best $400 I have spent in a long time.

[bowtie427ss]

Corner placement can do wonders for low end reinforcement. When you mentioned that you were going to push them back into the corners i knew there was no point in mentioning this because you were going to find out first hand soon enough.

Something that OG's post reminded me of, and i would emphasize is that exact 418/421 cones and other rebuild parts are NLA. Yours look to be in quite excellent shape, beauties in fact and to parrot OG, the quantity surviving in that condition is limited and shrinking slowly. Take care of em, maybe rotate em 90-180 degrees once a year or so to prevent any sagging of cone or suspension. Sometimes i forget that those shiny Altec aluminum dust domes that were once very common will someday be pretty much extinct.

Just for clarification, when i mentioned reconing them in a previous post i was only referring to in the event they were damaged from over excursion or over powering. I don't want you fellas thinking i'd tear perfectly good working and looking cones out for the sake of replacing them with something else.