Reconing 15" bass drivers on JBL 4350A's: Need a pro shop

[grumpy]

Comments on the vendor video:

Personally, I've found that running a 30Hz tone brings out alignment issues (allowing them to be noticed and corrected) better than finger pushing, but I would expect the latter to be quicker and require less equipment (zero). If there are no alignment issues, either is probably sufficient.

I always cut out the foam surround where the screws pass through the frame (after gluing the foam, and prior to reinstalling the gasket). Last thing you want is to torque down the mounting screw to have the foam rotate and distort. If you're using clamps (vs screws through the frame), this isn't an issue.

Cleaning (and gluing to) the backside of a cone is a bit trickier than what was shown for the C-V front-side example in the video, but take your time. Presumably the written instructions with the kit will describe the process for your drivers.

[j20056]

Thanks Grumpy, you guys are really great.
I actually highlighted the problem (present on all 4 drivers) by running a 25-30Hz sine wave through the 4350's. But to be honest, I am unfamiliar with the alignment issues that you mention. Is it improper alignment of the coil in the magnet field? presumably, poor alignment would create screeching sounds or worse? The video indeed appears to simply push down on the center of the cone to make sure everything is aligned. But I am unsure if I'm supposed to do more advanced alignment testing?
Lastly, good point on holes where the screws would go but i do use clamps so not relevant here.
Thank you so much again and now, as i am waiting for the parts, I will begin the preparation process, which appears to be the most complex part of the project. I started removing one of the foam surrounds from one driver and they fraying in my hand like sand, I can't believe I didn't notice it before, as the distortion was reasonably low despite playing the speakers well above 110dB. Speaks of the quality of vintage 4350's...

[grumpy]

non-interference in the gap primarily (throughout travel range). Ideally, the voice coil is both centered concentrically in the gap as well as moving on-axis only
(not tilted). Assuming spider (corrugated suspension connecting the frame to the voice coil area on the cone) isn't worn out, the static position of the voice coil in the gap (height) should be ok. If the spider is obviously not 'flat'... inner corregation bumps are either sunk in or extended out vs the part of it near where the frame attaches... it will take professional (or at least more advanced) help to select and replace that particular part.

Noises can come from other moving parts as well, such as lead tinsels (from wire terminals to where they go through the cone to the voice coil)
needing to be adjusted so they don't hit or rub things. Finger pushing test won't excite this type of non-musical behavior.

[SEAWOLF97]

Comments on the vendor video:

Personally, I've found that running a 30Hz tone brings out alignment issues (allowing them to be noticed and corrected) better than finger pushing, but I would expect the latter to be quicker and require less equipment (zero). If there are no alignment issues, either is probably sufficient..

there's one nice (but yet to be mentioned) benefit to ordering from RCobb = a CD with the 30hz tone is included with the surrounds order.

[j20056]

I'm back with a question. I am done cleaning up the first driver, removing rubber and glue. However, my question is about the rim of the paper cone itself. As can (hopefully) be seen on the attitude photo, there is a rather rigid black rim of hardened glue+rubber at the edge of the paper cone, permeably 1/4 wide. I can remove it by softening it with alcohol and cutting carefully, but before I do that I wanted to make sure that it is not a part that needs to be kept. it is definitely harder in consistency (and harder to remove) than the easy to remove black rubber that was about 3/8" wide at the back of the cone.
So wondering if I should remove it, as if I do so, only a clean paper cone edge will be left, prior to gluing to the new rubber surrounds.

Thanks for your feedback.

PS: Although the metal frame is not 100% clean metal, the video from SimplySpeakers states that as long as it well cleaned, it doesn't need to be 100% void of residual glue and rubber.

[1audiohack]

Hello J

It’s a bit hard to tell from the picture since the immediate background is also black but I believe the felt edge of the cone should be all that is left.

Barry.

[Earl K]

When I look at this pic, I see a shiny black edge almost 1/2" wide ( close to touching the edge of the basket rim ) that needs to be removed.

NOTE: don't remove anything until you have your new foams in hand so that you can make sure you don't remove too much edge.



Google "2235 refoam" + I'm sure one will ( eventually ) see what a properly prepared edge ( of a 2231 or 2235 ) looks like.



Okay, I did it for you;

See ( click the pic for more info );



Here's a 2231 cone that shows the proper space ( gap ) between edge of paper cone and the metal frame edge ( note: that paper cone still needs some cleanup )