Question on redoing the foam surrounds.

gudnoyez

On my beloved JBL L15's , I will post the before and after picture to see if any of you think my prep job is sufficient before I glue the foam surrounds on here goes





I used rubbing alcohol and goo gone along with an exacto knife to remove all the old glue off the gaskets and cones. I worked an hour on just this one. I used rubbing alcohol sparingly on the back side of the cone and scrapped the residue gently with my fingernail, the back of the cone was the hardest part. I hope the prep job will do what do any of you say. I will do the next one tommorow if anyone thinks the prep job is sufficient.

gudnoyez

On the 2nd picture how should I go about getting the black spot of the front rubbing alcohol also?

teekay0007

gudnoyez wrote: »

I will do the next one tommorow if anyone thinks the prep job is sufficient.

Have at it, Stevie! Go nutts!










Actually, might want to wait for the green light from someone who actually knows what they're doing here....where's WMG?


I am only using Polk speakers, currently. They have butyl rubber surrounds that don't seem to want to rot out - some at nearly 30 years of age! Good stuff!

gudnoyez

Thanks guys, yep I'm waiting for WMG'S approval and hoping he can give me a tip on an easier way to get the residue off the back side of the cones I'm worried about using to much rubbing alcohol and didn't want to damage them. I swear JBL must of used tar instead of glue the gasket was covered in that black stuff but I got the back side of them pretty clean. Terry you know me by now the Polks out number any other brand 10 fold in this house, I do have a soft spot for Acoustic research and JBL'S though.

mhardy6647

Basket and cone look OK to me.
Not sure what 'black spots' you're worried about?

Are you planning to shim the VC or not?

What adhesive are you planning to use?

IME (and FWIW), smaller drivers are generally easier/more forgiving to re-surround than are larger ones. This driver looks pretty small, so that's (I'd opine) a good thing

The other important variable (again IME/IMO) is how big the gap is between VC and magnet/motor... some woofers (e.g., the EPI woofers) are very forgiving; some other drivers have very little play in the VC gap and need to be carefully aligned -- else the VC may drag. Some of the JBL drivers are pretty tricky, methinks. Dustcapectomy and shimming may be indicated in the present case; you may wish to arrange a consult with other specialists before beginning the operation

pitdogg2

the edges look good. In most cases you do not need to get 100% of old glue off, as long as the foam is gone you should be good. I have used the glue the new foam came with but westmassguy turned me on to this
https://www.amazon.com/Aleenes-Original-Tacky-Glue-4-Ounce/dp/B005Z463A2

you can find it everywhere including walmart.

Go slow do one edge at a time start with the cone first then 24hrs later glue to the frame. put a little on the edge of both paper and foam let set for a few then drop in place. you may need to keep running your finger around the edge until it grabs just keep close eye on it. This is the reason I do only one at a time when you have two going at the same time it can get very hectic quick. I have only found a few woofers that I needed to cut the dust cap JBL and infinity being two of them. If you feel you can do it with out well they are yours I've done about 20 woofers and unlike Mark (mhardy) I find the larger woofers MUCH EASIER because you can get your fingers in where they need to go. just go slow you should be fine.

Woofers that had the foam on the back can be tricky to see good be very careful some you can put on the front depending on the foam angle.

mhardy6647

Just to clarify -- the only (two) times I had alignment problems issues challenges were with 15 inch woofers. I've yet to have a problem with any smaller drivers. Yet. (and, in full disclosure, I've also done problem-free re-surrounds of 15 inch woofers).

westmassguy

Be very careful with those cones. The Aquaplas coating can be very brittle, and chip off. @mhardy6647 is correct, those old JBLs can be a PITA. Voice coil alignment is critical. Unlike some, the JBLs have very large diameter voice coils/formers, short in height, and tight air gaps. Cerwin Vegas of similar size, have air gaps you could drive a truck through. I would never do a JBL from that era without shimming. As for removing the goo in the back, try flipping the woofer on its face, and scrape off as much as you can from the backside, between the spokes of the basket frame. I have several cheap, narrow wood chisels, that I keep sharp, and by running them along the edge from the backside, you can remove all the old foam particles. DO NOT apply too much pressure. You'll never get all the old gooey glue off. Use Aleen's Tacky Glue for the new surrounds. For the front frames, I use a combination of mechanical (wood chisel) and 90% alcohol to get the old foam and glue off. Glue the surround to the backside of the cone first, and line it up as perfect as possible. Try dry fitting it first. Some surrounds are slightly larger or smaller than original, and rear mounting is much more difficult.

teekay0007

gudnoyez wrote: »

On my beloved JBL L15's...

How "beloved" are these JBLs, Steve? Is this a good starter project?

Just throwin' this out there: If they are of huge ("Yoooj!") value to you, you might want someone who's very experienced at this to have at it. They don't look very "shippable" in their current state, so you could drop them off with me on your next pass through (deer hunting?) the Twin Cities. I could take them to Midwest Speaker to have them refoamed. When completed, I could have them ready for you to pick up on your way back through, or have them shipped back to you from your local discounted shipping hub.

If their "value" isn't that great, then disregard the above statement, get the advice of the more knowing around here and have at it.

If/when you attack this, do post some pics along the way.

teekay0007

mhardy6647 wrote: »

Are you planning to shim the VC or not?

That's what she said...

gudnoyez

Thanks for all the info guys I got both of the baskets and gaskets spotless I can say that the back of the cones are not. I got a lot of it smooth when you run your finger along the back of the cone but it's not completely removed.

I don't want to saturate the cone with rubbing alcohol so I'm going to let them sit until tomorrow evening and give it one more go, does the old dried adhesive have to be completely removed from the backside of cone for the new surrounds to adhere properly? I need to know how the heck do you shim the voice coils? There is some information that simply speakers provided with the purchase of the surrounds but nothing is mentioned about completely removing the excess on the back of the cones or how to shim the voice coils.

lawdogg

Of the JBL woofers I've re-foamed, I've never had a problem both leaving any hard-to-remove adhesive bits and leaving the dust cap in place, not using shims, and using a 30Hz test tone while the glue dries to ensure the voice coil is centered.

A good trick is to glue the surround to the woofer first and let it dry. Then put the glue in place on the basket and let the test tone play while it dries.

westmassguy

Shimmed woofer voice coil formers:

pitdogg2

Index cards cut down is what I have used. In most instances you can buy new dust caps for the same seller you bought the foam from. You'll need to measure the cap and most times just generic.

gudnoyez

Finished I guess I won't know how I did until they are back in the cabinets which are a state away heading up there soon.I will dynamat the baskets once they are dry.