??? If by needing recharging, I assume you're talking about draining, re-magnetizing an AlNiCo magnet, which is indicated by an increased Qes, so driver #1 is a little 'weaker' and both are a bit 'weak' relative to any OEM 416 AlNiCo I've either measured or seen measurements of, though at least recent re-cones can be much higher, a problem that Pano and others have had.
If yours have Ferrite ['mud'] motors, then they should never need re-magnetizing unless cracked or large chunks missing, but then the frame is usually damaged also, in which case it makes a nice woodworking dead weight clamp.
GM
If yours have Ferrite ['mud'] motors, then they should never need re-magnetizing unless cracked or large chunks missing, but then the frame is usually damaged also, in which case it makes a nice woodworking dead weight clamp.
GM
Other than a measurement error, I've no clue. I mean I know that a shorting ring is the common way, but Altec only used them on the original 288 AFAIK and later diaphragm replacements require modding the driver to accept them, so can no longer be 'original', a good thing to know if ever contemplating buying some ridiculously overpriced 288s.
GM
GM
Maybe you are saying i should have bought new, dunno. These were a fairly good deal for their condition. Maybe not. Much less than new. Here is a pic of the cone. Is original based on all info that I have access to for the Orginal Altec 416's. Perhaps box measurement will reveal more.
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I would have said so, if that was the case, though I have periodically posted that all things considered, buying new is a good plan if AlNiCo as there's no guarantee that they can be restored to like new.
FWIW, I've [re]zapped literally thousands of small electric motor AlNiCo, ferrite and cobalt mags and it's a real crap-shoot getting a good and especially, consistent, charge, so much time is spent redoing the worst and matching pairs, then batches, to determine their marketing value.
Note too that I only recently learned that GPA re-cones will have somewhat higher Qes/Qts by design since really low Qts motors were no longer required once very low output impedance amps became the norm, so only becomes an issue if using a SET or matching impedance amp.
Not that GPA cant't make/re-cone a low Qts motor, it can as proven by measured specs of their ferrite 515GHP series, but for 416 AlNiCo it seems to not be the norm, so I'm guessing it would have to be a [$$$] special order.
Regardless, your's Qts fall in line with Altec's later 416B published specs so good for all but matching impedance amps, so appears that you got a good deal overall if you saved some bucks.
GM
FWIW, I've [re]zapped literally thousands of small electric motor AlNiCo, ferrite and cobalt mags and it's a real crap-shoot getting a good and especially, consistent, charge, so much time is spent redoing the worst and matching pairs, then batches, to determine their marketing value.
Note too that I only recently learned that GPA re-cones will have somewhat higher Qes/Qts by design since really low Qts motors were no longer required once very low output impedance amps became the norm, so only becomes an issue if using a SET or matching impedance amp.
Not that GPA cant't make/re-cone a low Qts motor, it can as proven by measured specs of their ferrite 515GHP series, but for 416 AlNiCo it seems to not be the norm, so I'm guessing it would have to be a [$$$] special order.
Regardless, your's Qts fall in line with Altec's later 416B published specs so good for all but matching impedance amps, so appears that you got a good deal overall if you saved some bucks.
GM
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THanks GM. Everything I have read seems to agree with your statement abour remag. Guys on audioheritage described what they called a crap shoot involving Orange county remag. Said only way to do it right was without cone. Measure, magnetize and recheck. They will be driven with a SS amp, although the F1j had crossed my mind. More likely candidate is NElson's F4. Dunno. Amps wont be a problem. THanks for the time. Forgot a jigsaw, so no box measurement tonight.
Side question. THese are rear mounting woofers. I am used to front mounting style. LYnn suggested that in 800Hz and below range it is not important for them to be flush mounted. Would you agee? One thing I notice is that the cone profile of the ALtecs are much deeper, resembling a waveguide in comparison to shallow JBL2226 profile.
Side question. THese are rear mounting woofers. I am used to front mounting style. LYnn suggested that in 800Hz and below range it is not important for them to be flush mounted. Would you agee? One thing I notice is that the cone profile of the ALtecs are much deeper, resembling a waveguide in comparison to shallow JBL2226 profile.
You're welcome!
They must not do a good job draining them, or worse, don't drain them at all, which means they will never take a deep charge.
FWIW, drivers are assembled with dead magnets and magnetized right before going to the testing area, so can be drained/recharged assembled, but it's how well it's drained that matters most.
A 15" driver's cutout has a ~280-290 Hz eigenmode with a 'piston' radiation polar response around 900-1 kHz/160 deg. and a ~1265-1270 Hz pipe resonance, so tapering is strictly cosmetic below a ~760 Hz/2nd order XO point unless a very deep baffle is used.
Deeper = stiffer. Altec primarily relies on 'fast' material wave speed and doping to achieve its sonic signature whereas JBL relies more on flexure and why it has all those annular rings that each are in effect a mechanical XO.
GM
They must not do a good job draining them, or worse, don't drain them at all, which means they will never take a deep charge.
FWIW, drivers are assembled with dead magnets and magnetized right before going to the testing area, so can be drained/recharged assembled, but it's how well it's drained that matters most.
A 15" driver's cutout has a ~280-290 Hz eigenmode with a 'piston' radiation polar response around 900-1 kHz/160 deg. and a ~1265-1270 Hz pipe resonance, so tapering is strictly cosmetic below a ~760 Hz/2nd order XO point unless a very deep baffle is used.
Deeper = stiffer. Altec primarily relies on 'fast' material wave speed and doping to achieve its sonic signature whereas JBL relies more on flexure and why it has all those annular rings that each are in effect a mechanical XO.
GM
Fs/Qts is well matched, but Vas is way off if accurate, so depending on room conditions and how big a cab used the bass may sound a little lean on the lower Vas one.
FWIW, the Le value should be at 1 kHz, hence the very low values I questioned.
GM
Yeah, just as the sealed cab needs to raise the driver's Fs at least 1.56x, so too must the added mass method lower Fs by 1.56x [0.641 x Fs], so a few quarters or steel washers isn't going to be enough. Near the end of my active building 'career', I got so lazy that I just clamped the driver to my 2.25" thick solid wood workbench since my cab alignments were typically large enough that Vas wasn't a major factor in how it performed.
GM
GM
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So i plugged the numbers into MJK's confirmation sheet and something is clearly wrong. Using presceibed Vas from driver 1, his sheet show a much lower BL ans Mms. Odd thing is, measured numbers aren't off far from the Altec listed numbers. Tried doing it the opposite way and entering BL trying to find VAS, things are closer, but Vas is way down