Wednesday, June 13, 2012

JBL 2268 recone

Hey there!   Here's a video I made about a modern  JBL 18 inch speaker for subs. Model 2268.  This is the first video so lets see if it works.

The JBL 2268 speaker has a neo magnet and the frame is aluminum which results in a very lightweight speaker.
It has two voicecoils for better damping, more power handling and less power compression which means its more accurate at higher power levels.  As you can see in the video, this speaker dried out and blew apart, creating an imbalance that eventually made the voice coil fail.

The video shows how and why the speaker failed.

I got an aftermarket recone assembly from McKenzie.

McKenzie reconekits

The recone job went well and the speaker went back into service at The County Line club in Melbourne Florida.

My other site fix-any-thing also has posts about fixing speakers.

BTW if you see something interesting on those little ads, please check it out and then come on back.

Thanks for visiting, I hope I can help with your speaker problems.


Monday, February 27, 2012

Spiders and Voice Coils

Here is an example of a spider,/voice coil, and lead wires.  This eventually became the speaker that's pictured above.  The white glue was removed and the spider as well.  The voice coil was still good so I experimented with spiders, cones and a red Cerwin-Vega surround.
 You can see how they are glued together.  The paper cone has been removed from this assembly.  Note how the flexible wires pass through the leftover piece of cone material.

This is a JBL D-130F during the recone process, before gluing.
Can you see the clear plastic shims that hold the voice coil in place?
The copper ribbons lay onto the cone after the cone is glued in place.

Here's how the wire looks coming through the cone to the speaker terminals.

Working EV coil, Weber spider and flex wire, salvaged cone.
If you're lucky, you can find a pre-assembled speaker recone kit that looks something like this one by searching for 'recone kits'.
Except I didn't glue on the surround yet in this photo, which would be included in a pre-glued kit.
The surround goes around the edge of the cone and is glued to the frame at the same time as the spider.
The white stains on the coil are from fumes given off by the super glue.
I use a slow setting, 1 to 5 minutes, rubberized cyanoacrylate by Loctite to attach the coil,cone and spider to each other.  This must be done withe parts carefully alligned in the correct position on the frame with shims holding the voice coil in place. The coil of wire must be centered in the magnetic field.
This unit was fitted to an EV 12" frame.

This is what happens to a voice coil when the magnet shifts in a Mackie horn driver.

You can see that the gap is a different size in the two photos.  Maybe not so obvious but the voice coil was pinched and the only way to fix  this is to have a very large and expensive machine to demagnetize the
magnet, re-position it and glue it, then re-magnetize. I just got a new one instead for $75.  Don't bother with shifted magnets unless you have an extremely rare and valuble speaker that can't be replaced.

The speaker cabinet must have taken a violent fall to break off this part of the horn and shift the magnet.

I was able to solder that tiny wire on this vintage hi-fi tweeter..
You can't tell by the pic but that coil is only about a half inch accross.