The Re-coned 416-8C's

[RonSSS]

I **** at typing......

So I have 2 cones that I have not yet installed.
Will Bill replace these for me?

Ron

[Todd W. White]

I didn't ask that question - contact him and see...

[RonSSS]

Thanks for the info Todd. I'll try and give Bill a call in the next day or so.

Art. I looked carefully at the cone from GPA and I believe that the surround is installed correctly, just on the wrong side of the cone. There are 4 outward pleats showing, and that matches with a stock driver.
So I agree this isn't the whole story, but it's a step in the right direction.
I still tend to think the cones are shorter, but as I said, it's a difficult measurement to make on a disassembled cone. If I had a New Old Stock cone, it would be easy.

Maybe Bill will share with me the procedure for doing a re-cone......and I might buy the glues from him as well.

Ron

[bfish]

Here's the procedure (text only) copied straight from the Altec instruction sheet. The sheet was new enough, I wouldn't be surprised if Bill wrote it. As I mentioned earlier, almost all Altec 15s are listed on it except 416s and 411s.


Step 1. Remove speaker from enclosure or
mounting baffle and take it to the work
area.
Step 2. Unsolder tinsel leads from inner side of
terminal posts, or unplug from terminal.
Step 3. Remove gasket ring (or gasket-ring
segments), cone, spider and voice-coil
assembly.
Step 4. Cover voice-coil gap with masking tape
to prevent debris from entering gap.
Step 5. Remove old cement from mounting
surfaces of spider and cone. Use a single
edge razor blade in a holder to lift cement
from mounting surface. If necessary,
scrape residue and/or clean surfaces with
suitable solvent such as methyl ethel
ketone (MEK) or cyano- debonder.
Step 6. Remove masking tape from voice-coil
gap.
Step 7. Clean foreign material from voice-coil gap
with a short strip of 1-inch-wide masking
tape. Fold tape back to form a strip with
adhesive exposed on both sides. Insert
edges of folded tape into voice-coil gap to
full depth, and wipe clean completely
around the circular perimeter. Repeat
cleaning procedure several times with
fresh tape until tape remains clean when
withdrawn.
Step 8. Apply proper cement to surfaces of
speaker frame where spider and cone rest
(see Table of Cement Applicability and
speaker illustration).
Step 9. Place new cone assembly loosely in
position and insert centering shims
between pole piece and voice-coil as
shown in the illustration detail. Carefully
center voice-coil.
Step 10. Fasten spider by pressing it down against
cemented surface of speaker frame,
completely around perimeter of spider.
Step 11. Fasten outer edge of cone by pressing it
down against cemented surface of speaker
frame, completely around perimeter of
cone.
Step 12. Cement gasket (or gasket segments) in
place. Allow at least 4 hours for cement to
set.
Step 13. Remove centering shims and verify that
no foreign material is in voice-coil gap.
NOTE
A clicking sound may be heard if leads are
short-circuited, and cone/voice-coil assembly is
depressed in gap.
Step 14. Solder leads of voice coil to terminal posts,
allowing enough slack for full cone
excursion, but not so much that leads can
touch one another or the speaker frame.
Plug in tinsel to terminal on these models
with terminal stake.
Step 15. Place dust dome in position and apply a
bead of cement completely around outer
edge of dome.
Step 16. Apply two or three coats of solvent based
surround dope in area shown by
illustration. Apply one coat of water based
dope in area shown by illustration. See
Note 1 of Cement Applicability Table.
NOTE
Use an acid brush or suitable bristled brush.
Step 17. Allow 24 hours to dry before reinstalling
speaker.

[Art J.]

Wow
I didn't know that would make a difference.
-------------

Boy Ron, this story keeps getting better. That little distance
between the inner and outer edge can't be all of the problem.
Is their a slight pitch (in) on the inside edge of the surround?
Sight unseen.
Since it was glued from the bottom, the whole surround could
be inside out, pushing in, instead of holding out. Oh No....

[RonSSS]

Thanks Bfish,
This procedure assumes that the Cone and V/C is an assembly. Which it isn't in the case of the GPA parts. You have to glue the V/C assembly to the cone.
Ron

[bfish]

10-4, I've come across the variance on the spider/cone joints, with some having up to an eigth gap, and others touching, both on ones I took apart, and completed jobs, yet I never ran out of former, nor had to trim it.

Then there's the chance that a 416's an entirely different beast since not listed, though I can't imagine why, unless its the doping procedure. The oversize, vented dustcap is the only major component difference, assembly-wise, but all the 515s were listed, which use the same cap. I can see the 411 being on another sheet, with the foam compliance.

Anyway, best-of-luck to you in finding a satisfying answer (and some peace!).

[RonSSS]

I believe I have it all figured out, I just need to see if GPA will sell me the glues, and then decide if I want to have a go at it myself.

Would you recommend a series of shims? I was thinking of making a tubular shim from either brass shim stock or maybe some sort of stiff plastic sheet stock. Looks like .012" ought to do well. I'll have to go see what we have in the model shop....they used to be able to build most anything there. (Tektronix)
Ron

[amh]

Ron,

Do you still have the old stock cone you disassembled? I think you said you even removed the VC from it? If so, just lay it on a table top, surround end down, then stick a scale (ruler) through the small end to the table top. Measure the height from the table top to the edge of the small end (where the VC would glue in). Repeat with the GPA cone. Compare the height.

Cone mass you can get at your local post office or drug store. Anywhere that has an accurate scale.

Not trying to be pushy, but the suspense is killing me!

[RonSSS]

Hey guys.

AMH.....I went back and measured the cones.
The old cone...as best as I can tell, measures 3.60" from the small end to the table. The GPA cone measures 3.4".
Again, it's real hard to remove the VC w/o messing up the cone, but I did 2 of them, and I believe the 3.6" measurement to be correct.
So a difference of .200". The GPA cone is shorter.

The GPA cone is also .004" thinner than the orig cone. So no doubt, lighter as well.
And....to my eyes the shape is different as well. The original cone has more of a trumpet shape, the GPA cone is more like a funnel.

I really think this explains the sunken cone syndrome. But, one can eliminate this by making sure the cone doesn't sit all the way down on the spider when doing the gluing. And there is plenty of former left to glue to. I carefully shimmed and set all of this together again tonight.

Not sure how the cone differences will affect the sound though.

Bfish......got it about the shims. I played around with .010 plastic shims tonight. I could get 5 in, but the 6th just wouldn't go.
Explain doping please? Almost sounds like you do the whole cone? This is confusing.

More good info folks.

Beginning to make me think it's worthwhile to search for nice original drivers. A NIB pair of 416-8B's sold recently on Ebay for $600. Could have been a bargain!

Ron