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JBL L40 10' woofer surrounds?

patfont

patfont

AK Subscriber
Subscriber
Hi guys, 1st timer here in the speaker forum. Who do you guys like to use as the defacto standard go to for foam surrounds for JBL. Need to refoam a pair from the attic going back into service. JBL L40's 10 inch woofers, Thanks!
 
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I have used Simply Speakers many times with excellent results. Some have complained not to like the glue that comes with their kits but I have had no problems. Prices are competitive and same day shipping is the norm. They also support AK with their ads. You can order by phone or over the net. I did a set of L40. They turned out nice.
 
JBL owners will always recommend Rick Cobb. You'll have to do a Google search of this site for contact info. I'm traveling and replying on my cell phone.
 
Rick Cobb AHA "Looney Tunes" on Ebay as well as MSound- great kits for beginners.
DC
 
BMWCCA said:
JBL owners will always recommend Rick Cobb. You'll have to do a Google search of this site for contact info. I'm traveling and replying on my cell phone.
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Rick is the man when it comes to JBL surrounds. Have ordered from him many times and always had a good experience.
 
ok thanks everybody I am going to contact Rick.

I like the rather large dust caps on the L40's can I leave these on, or do you have to cut them and remove them to put shims in?
 
patfont said:
ok thanks everybody I am going to contact Rick.

I like the rather large dust caps on the L40's can I leave these on, or do you have to cut them and remove them to put shims in?
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Using the Rick Cobb method of surround repair, you don't need to remove the dust caps. What I have done is having the woofer on its back face up and using gravity as your friend, clean off all the old surround from both the cone and the frame. As for the cone be careful not to shred it up. I use the roll the edge gently between thumb and forefinger to clean it up.

Bottom line, be patient. :D

Oh and pics help too.
 
ok here comes some pics:

can i try to re-use the black type felt rubber on top of the foam around the speaker frames?



 
Yes you should re use those. Get as much of the old glue off as possible from the foam strips and the frame. I use Goof Off on the frame, but you need to use it in a well vented area. The thumb/forefinger is a good method for the cone.

Edit: You can also turn the driver on it's face on a piece of plywood/mdf and gently push the cone so that it touches the wood, then you can work the edge a little more aggressively with an Xacto flat chisel blade with the handle positioned at a slight angle to the cone to scrape the rest of the foam from the edge of the cone
 
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juniorJBL said:
Yes you should re use those. Get as much of the old glue off as possible from the foam strips and the frame. I use Goof Off on the frame, but you need to use it in a well vented area. The thumb/forefinger is a good method for the cone.

Edit: You can also turn the driver on it's face on a piece of plywood/mdf and gently push the cone so that it touches the wood, then you can work the edge a little more aggressively with an Xacto flat chisel blade with the handle positioned at a slight angle to the cone to scrape the rest of the foam from the edge of the cone
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Yes you always try to save the gaskets. JuniorJBL, never thought of trying this and just a reminder why these forums rock! :D
 
All done and sounds awesome with that typical JBL punch and drive. Guys thanks for the Rick Cobb info, the 30Hz coil centering tone works perfect, and makes the job so much easier. I also added some new beauty rings/speaker gaskets so they look finished.:music:

Gonna hit the cabs with some Howards now!


 
Awesome job! Keep in mind that a few hours of use is required before those will surrounds loosen up. :D
 
Bigyank said:
Using the Rick Cobb method of surround repair, you don't need to remove the dust caps. What I have done is having the woofer on its back face up and using gravity as your friend, clean off all the old surround from both the cone and the frame. As for the cone be careful not to shred it up. I use the roll the edge gently between thumb and forefinger to clean it up.

Bottom line, be patient. :D

Oh and pics help too.
Click to expand...

I hope this is an ok place to jump in with this. I have a pair of L40s that I have been procrastinating on refoaming, and I finally pulled them out today and hooked them up to get a level set on what condition they're in. They were a curb find a couple years ago. I saw that the foams were toast, but knew that that was a straightforward repair, though I'd never done it, so I lugged them home and there they sat.

So the foam surrounds have been removed, I have not yet cleaned up the frame or the cone, but there's just the gap there between the cone and frame. They're sitting on their backs on the carpet, and I ran a tone generator through them (also some music). A couple of observations/questions:
  • Considering their current foamless status... they sound amazing. I have not been much of a JBL lover most of my life but I think with the deterioration of my high frequency hearing, they have become quite nice to me! Sort of a joke / sort of not. I'm impressed with the sound. But...
  • When does a refoam job become a recone job? How tight are the tolerances on these voice coils? I have read the techniques for refoaming, and I already have the Rick Cobb kits. But I am worried that I may actually need more than just a refoam job. It is very difficult to get the woofers to play noiselessly, i.e. without vc rub/scratchiness. There is a sort of sweet spot, if I'm very careful I can find it. Is it foolhardy to think that I'll be able to find it when I'm gluing the surrounds in? Are they more likely to go in a straight in and out direction once the surrounds are attached than they are now? Is part of the problem the fact that they're literally flopping in the breeze by virtue of being unattached at the edge?
  • Second, assuming that a couple of you feel that I should go ahead with the refoaming and see how it goes, am I being wrongheaded by thinking about gluing foams onto the tops of the cones rather than underneath, and that way not having to worry about possibly damaging the cones by trying to remove the remnants of the old surrounds on the underside? Or should I just proceed with caution, clean it up and glue under the cone?
Would look forward to any advice from those who have been there before! (And if this should be posted elsewhere, I'd like to know where cuz I couldn't really find a better place). Thanks.
 
Rick Cobb used to send a CD will about 2+ minutes of bass tone on it- if you get surrounds from him please asj and verify.

JL's and a few others have very tight tolerance vocel coil gaps- as the designer intended. This helps make, as do other things, a precision product. Using the test tone method of re+foaming centers the VC gap easy and also helps in centering the frame to the foam. You do not need to take a chance of clipping a CV lead wire or fussing around with a dust cap at all. Turn on the amp to a low power setting, apply glue to the outer frame , center the surround to the frame and let set up, for an hour or do. Apply glue to the foam and let that set up on the cobe and inner foam. There are all kind of tutorials about this. BE SURE you glue to inner foame to the top of the cone or to the under under side of the of the foam If I remember correctly you glue the inner part of the foam on top of the inner cone.

Recone job are those where the cone is badly torn, a voice coil is shorted or open typically.
You do not want to play a wooer without a proper fitting foam. Running a wooer like that can cause the delicate VC wire to scrape into the pole piece, scrapping the thin enamel coating off VC wire can cause the winding the touch one another.

You will want to carefully remove ALL the old foam debris. Paint remover works great for me. Relax, take your time and the the glue set up. If it goes where you do not want it take a couple damp paper towels ancl clean of the excess. If the paper cone get a little damp it will dry OK

Hope this helps,

DC
 
It does help, of course, and thank you very much! I will be using the tone-centering method, the "Rick Cobb" method. I think you answered the issue of the tight VC tolerances. I wasn't running it too hard without the foams, so I hope I didn't do any of the chafing damage that you described! I will forge ahead and hope for the best. It seems that you're describing gluing the surrounds on the top side of the cone, which I would love to do and then not have to remove the remnants of the previous foam. But I believe the originals in this case were glued to the underside of the cone, and I don't want to offend purists / future possible buyers. I guess I need to grab a good single malt Scotch and go to work. No, I won't use it on the speakers.
 
Sorry for the typos- I was in a hurry to reply! Hope all goes well none the less.
Double check where it is the foam properly glues to the cone- front or back as I have forgotten which way to be sure. Doing the right & proper way will keep the resale value and purist off your back!
DC
 
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