JBL L46 - Magnet took flight! Voice coil dangling in the wind.

[EvanF]

The woofer is a tough b***h, bonded itself to the chipboard. I tapped the magnet with a mallet to get it free so I could refoam it, and the damned thing fell off!

http://imgur.com/mmPKdT9

So how screwed am I?

 

[geiman]

Wow that's terrible! It's really hard in my experience to remount a magnet and get it aligned properly.
If I was you I would contact Gordon W on this forum for advice. If it has to do with speakers and their construction he has already done it.

 

[turboyam]

I would do like if you refoamed it, take the dust cap off, use shims in the voice coil gap. I would use a good epoxy mix on the magnet. Certanly repairable, unless the voice coil is damaged.

 

[Chris Brown]

I agree that treating it like a refoam is the way to go. The magnet is a very simple piece of the speaker. It just sits there, and isn't directly attached to anything but the speaker frame. It's the voice coil (basically an electromagnet) that is the complicated part. I would pass on using shims though, as that usually requires you to butcher the dust cap, and very likely never get it looking as good ever again. 30hz test tone method should be plenty if you go slow.

Does any part of the speaker (especially the voice coil) look like it sustained any damage as the magnet was detaching?

 

[woodj]

I'd do shims to assure accuracy. It's going to be difficult to align the voice coil with a magnet that ain't there yet using a tone.

 

[Chris Brown]

It's going to be difficult to align the voice coil with a magnet that ain't there yet using a tone.

The point of the 30hz test tone is to help make sure that there is no rubbing of the voice coil, which would occur after the voice coil is placed within the gap (by hand). The woofer will work once the voice coil is placed within the gap. The magnet could be adjusted as the glue dries if there is any rubbing. I'm not sure what you think the hold-up would be.

 

[WaynerN]

I would find a machinist somewhere to dial in the magnet structure for re-gluing.

 

[woodj]

The point of the 30hz test tone is to help make sure that there is no rubbing of the voice coil

As tricky as it is to center a "moved" magnet I would fear that without shims the voicecoil/former could be damaged.

 

[turboyam]

Re-coning or re-foaming is easy with a test tone, (and what i use is a DC power supply) but, this is lightweight stuff compared to moving a magnet assy, on the basket, with adhesive. A test tone alone won't do it IMHO.

 

[EvanF]

I agree that treating it like a refoam is the way to go. The magnet is a very simple piece of the speaker. It just sits there, and isn't directly attached to anything but the speaker frame. It's the voice coil (basically an electromagnet) that is the complicated part. I would pass on using shims though, as that usually requires you to butcher the dust cap, and very likely never get it looking as good ever again. 30hz test tone method should be plenty if you go slow.

Does any part of the speaker (especially the voice coil) look like it sustained any damage as the magnet was detaching?

Voice coil is in great condition!!! I figured there could be alignment tools for the magnet and the holes in the aluminum basket. Yeah, looks like tearing off the dustcap and using shims could be the only solution, I haven't refoamed them yet. These are not speakers I care to sell anytime soon. So, once I center the coil using shims, I should just place the magnet on the basket so that it doesn't rub? I figure I could do a very low voltage 10 Hz signal. DC might work.

 

[turboyam]

Use shims, and leave them there 24hours. Make sure the old adhesive is cleaned from basket and magnet.

 

[gtmechanic]

The woofer is a tough b***h, bonded itself to the chipboard. I tapped the magnet with a mallet to get it free so I could refoam it, and the damned thing fell off!

http://imgur.com/mmPKdT9

So how screwed am I?

I had similar problem with SAS woofer. Just send it to miller sound. My advise: do not attempt to do it yourself.

Loretta Legall
Millersound
1422 Taylor Rd
Lansdale PA 19446-1531
215-412-7700

 

[EvanF]

I had similar problem with SAS woofer. Just send it to miller sound. My advise: do not attempt to do it yourself.

Loretta Legall
Millersound
1422 Taylor Rd
Lansdale PA 19446-1531
215-412-7700

Thanks, but no thanks. I might build a jig like http://audiokarma.org/forums/index.php?threads/resetting-a-loose-magnet-with-pictures.202963/
RayW did and use his advice. Spending 150 on speakers I got for 24 dollars and refoamed using spare foams seems wrong...

 

[EvanF]

Use shims, and leave them there 24hours. Make sure the old adhesive is cleaned from basket and magnet.

What kind of adhesive do you recommend?

 

[turboyam]

24 hours epoxy. Magnet on it's back, you will see the magnetic gap, from the voice-coil hole ( no dust cap). This is very easy, you can do this, the basket is aluminum. A steel basket would be tough.

 

[gib48189]

I have been able to repair several speakers with magnets shifted, had to yank the magnet, clean up all of the old glue, etc. Was then able to make a cheap jig to re-align and glue the magnet in place. Just follow the thread referenced above. Not really too difficult, just take a little patience and time.

 

[EvanF]

I have been able to repair several speakers with magnets shifted, had to yank the magnet, clean up all of the old glue, etc. Was then able to make a cheap jig to re-align and glue the magnet in place. Just follow the thread referenced above. Not really too difficult, just take a little patience and time.

What epoxy did you use? Did the speakers sound good?

 

[petehall347]

if there are tell tale marks you could replace the magnet carefully then scribe a line before cleaning off the old glue .

 

[KingBubba]

Yeah, I tried this once on a pair of DCM CX-09s. What a flop. I did not take into the consideration that the JB Weld would flatten out and run and drizzle itself into the former. What driver is used in the 46? If it is the 117, it should not be too hard to find. The replacement of the magnet in exactly the right place is not an easy job, but you don't have much to lose.

 

[L200B]

I epoxied a similar JBL driver back together once. the magnet broke off right after I had refoamed it. I ran a tone through it and moved the magnet to get it centered. Worked out fine.