The Re-coned 416-8C's

[RonSSS]

Well,
I must have made a real *** out of myself.
Ron

[Mike Gibson]

Not really Ron. It takes a real person to admit making a mistake and even more of a man to post it where everyone can see it. Unlike a newspaper that when they print a retraction do so in the most insignificant way possible. A old bubblehead passed this little mantra on to me and I try and live by it "It is what it is." Simplistic for sure but when you think about it life can be a whole lot easier for me if I accept what is and move on. Looking at the positive side of this I'll wager you never make that mistake again Usually the magnitude of my mistakes are only limited by the number of people there to witness my blunders

[amh]

You're not allowed to play in any more of our reindeer games Ron

Just kidding, you fessed up to your math error. It doesn't change any of the other issues we were discussing.

Bet your happy your drivers match a little closer!

[RonSSS]

Thanks Mike and AMH,

Yeah, pretty embarrasing. Oh well.
I have been listening 2 these woofs in the 19's, and they sound quite good.
I still plan on investigating assembling my own when I decide to re-cone the 416-8B's.
I suppose I could at least take one of the old cones out and play with the new parts. I'd really like to try and understand why the cones get assembled sunk.
If I could find some time to use one of the lathes at work, I might even attempt a fixture for aligning the VC and Spider.
Ron

[Art J.]

Hello Ron, We have been in Paris for a while visiting a daughter and
it seems we couldn't trust leaving you home alone.

Well really, making and catching mistakes sounds like just a 'normal day at the shop' to me.
Your in great shape as long as you can catch them. I sure wish I had support
groups like this years ago when I used to bang my head against the wall.

Anyway, reviewing your posts, it seems to me that the 'surround' is the
dominating force that will determine how the cone will sit in the frame.
The distance between the surround and the spider will determine how the spider sits.
And then of coarse, the critical voice coil from there.

But assembling it is in reverse order though, so I can see problems if the 3 alignments
are not perfect based on the surround resting position. A carefully made assembly
jig based on the 3 critical points would seem to solve the problem.

Speaking of jigs, I made one last year just to replace the surround on my 411 woofer.
I wasn't going to take any chances on screwing it up.
I used clamps, L brackets, and 2 sided carpet tape to lock the cone in the
resting position "before" removing the old surround. It was a piece of cake
after that as shown in the pictures. You can call it over kill if you want but
I am very happy with the results.

http://img2.uploadimages.net/032029411sur1.jpg

http://img2.uploadimages.net/398689411sur2.JPG

[bfish]

Beautiful job on the 411s Art! Are those kitchen sink/countertop clamps?

After re-reading the Altec instruction sheet for reconing, I thought of another possibility for the 'sunken' syndrome. Altec recommends gluing on the front gasket(s) right after doing the cone surround, then inverting the speaker, to let its' own weight keep pressure on the gasket while curing. If the gasket isn't installed immediately, and in this manner, the weight of the cone assy could "pull" on the still wet cone/frame glue joint, and settle a little, as the spider won't hold all the weight in place by itself. If following the instructions, one must be very careful when inverting and setting down the speaker, so that nothing shifts in the process. Just another reason to leave the shims in place until everythings done and dry but the dustcap.

Since the gap in most Altec speakers is only a few thousanths larger than the coil (don't have one open, or I'd measure it), trying to recone one with the same procedures as more common speakers with sloppy tolerances just doesn't work, and their use of underhung voice coils further complicates things for the DIYer. For me, the speaker itself is the best jig to use, which is why I take the time to carefully get the coil in precisely the right spot, then uniformly add shim until the coil is actually locked in that position, especially with coils with paper or alum formers, which can deform soooo easily. Doing it this way means a new dustcap (or taking the time to remove the old one intact) for every job, even a refoam only. I do everything but the cap, then let it sit overnite. When you remove the shims the next day, you can check for and correct any problems you may find before the cap is glued on. I think this is especially important on a MI driver with an aluminum cap, since the cap actually fits over the end of the former, and could deform it if installed while the spider or cone joints are still wet. I find the hardest part of all to be getting a thin, pretty bead of glue around the cap, as it takes a very steady hand.

[Todd W. White]

Regarding the "sunken cone" problem -

One of Bill's OEM cone suppliers apparently did glue a batch of the cones together incorrectly, which made the cone look "sunken".

As far as Bill has been able to tell, though, the acoustic performance was not altered, at least noticeably.

As soon as this problem was found, it was corrected.

ALL recone kits and recone work done by GPA have been purged of the OEM-caused improper assembly. There have not been any sunken cones for some time now, nor will there be again.

[RonSSS]

Oh----kay.
Care to elaborate?
There is only one thing glued to the cone...the surround.
On stock stuff the surround appeared to be glued to the top edge of the cone. On what I got from GPA, the surround was glued to the bottom edge of the cone.
Is ths what you are talking about?
Dome details please.
Thanks,
Ron

[Todd W. White]

As I understand it, the OEM cone people glued the surround to the bottom of the cone, rather than the top.

[Todd W. White]

From what I understand (mind you - I haven't seen the problem you guys are talking about), the location of those particular parts when they are glued together makes a noticeable difference, visually.