View Full Version : Foam/Rubber surrounds for 125A's?

New At This
05-14-2005, 01:20 AM
I have come into a disassembled pair of JBL Decade 36 speakers. The woofers are 125A, 10", I believe. The woofers need to have the suspensions/surrounds replaced, and I'd like to try to do the job myself. A good share of the old foam is already off, and I've found some instructions on line for what to do. I haven't figured out what surrounds to get or where to get them yet.

However, I've also seen some descriptions of other JBL speakers that have rubber surrounds, rather than foam, and those descriptions always describe the rubber as superior to the foam.

Also, there's an open tube that leads from the side of the woofer to the outside of the front of the cabinet. However, no fastener or hood of any kind that would fasten it to the woofer came with the speakers. I wonder if I'm missing some part that I need, or if there's something special I need to do when I reattach the woofers?

I also wonder:

1. Whether there's such a thing as rubber surround replacements for 125A's;

2. If so, which of the two -- foam or rubber -- would be better to install;

3. In either case, where I should buy them; and,

4. Whether there's someplace local (I live outside of San Francisco) where I can buy them? I don't turn up anything on line so far from local outlets.

Thanks for any assistance.

05-14-2005, 07:24 AM
Rubber is ONLY superior, when the speaker is DESIGNED FROM THE BEGINNING to use a rubber surround. If the speaker is designed around foam, then the foam surround will give SUPERIOR PERFORMANCE, compared to ANY other surround material. It's a matter of matching the surround to the design of the cone assembly. Replacing a foam surround with rubber, will attenuate the midrange response of the driver, reduce the woofer efficiency somewhat, and generally change the "voicing" and tonal character of the speaker. With some poorly-designed speakers, this MIGHT be an improvement... but with a speaker as carefully-designed as a JBL, it will DEGRADE the overall sound of the speaker.

Bottom line- put foam surrounds back on there. Being in the SFO area, I believe you should be close to a place called Simply Speakers... I know they carry foam surround replacement kits. Otherwise, if you can't find anything, I can get replacement foam surrounds for you... they'll run about $6 each, plus shipping. Now, what Simply Speakers offers is a whole "resurround kit"... dustcaps, shims, foam surrounds, glue, etc)... what I have, is JUST the necessary surrounds. With these, I recommend using white glue or contact cement (Elmers or Weldwood is good), and the "30Hz method" (ie, play a 30 Hz test tone through the speaker while the glue is drying, and make sure it's centered (ie, not rubbing) correctly- it'll usually want to center itself, due to the influence of the test tone) to insure that the coil is centered. This eiminates the need to cut out the dustcap, since you won't need to use shims in the voice coil... making for a MUCH CLEANER appearance after the job is done, and a LOT less work...


New At This
05-14-2005, 01:58 PM
Thanks, Gordon, for the information. It was helpful throughout. Given my complete cluelessness about this, it sounds like the kit would be the best idea.

A couple more questions:

1. The only Simply Speakers company that I could locate is in Florida -- one address in Pinellas Park, another in Clearwater, I believe -- ). Is there another one out here you're familiar with?

2. Is a "standard" 10-inch kit appropriate for JBL 125A's?

3. Do I need any kind of gaskets as well? There don't seem to be any attached to the baskets...

Again, thanks for getting me sorted out on all of this.


05-14-2005, 02:30 PM
I must have mis-remembered... but, in any case, there is definitely Orange County Speaker, down in LA. If you need stuff sent to you, that'd probably be cheaper.

And yes, a "standard" 10" foam surround will work in the 125A. If you measure the cone diameter (without the foam) and the inside of the basket rim, where the surround glues on, and give OCS or whoever else you go with those dimensions, they should be able to fix you up. I actually have a standard surround I always go with on the 125As and 127Hs; I'd assume they probably have one too, but just in case, if you have those measurements handy, you should be quite safe...

There should be thin foam gaskets on those 125As. If they're not there, then you need to aquire some sort of thin gaskets to replace them (1/8" or so thick). It can be paper, foam or whatnot... it won't affect the sound of the speaker. I actually use a "trick" method... taking a thicker cardboard (paper) gasket, and peeling it down to the right thickness to properly fit in the recess of the 125A basket... works fine. IIRC, the gaskets made for a Cerwin-Vega LE10D 10" woofer, peeled down to 1/8" thick, will fit perfectly... they have FOUR bolt hole cutouts (instead of the 8 that most speaker gaskets have), so they will fit the JBL basket (which is also just FOUR holes) better than most others...


Bill Ding
05-18-2005, 10:00 AM
Hi GordonW

Where can I get a copy of the 30Hz test tone cd to refoam a pair of JBL L-50's?


06-08-2005, 09:23 PM
Does anyone know if there should be some type of gasket between the back of the woofer and the baffle? I've read other threads about them being needed to get a good seal and that weather stripping has been used. But neither my L36s or L50s had any type of foam gasket there. There was no residue to indicate there ever was. The L50s do have a thin paper gasket. Is it unnecessary to get a seal there because they're ported?

06-08-2005, 09:26 PM
The L50 had a paper gasket to which an "acoustic resistance shell" was stapled.


06-08-2005, 09:39 PM
Yup. We used to call that insullation. Is there any reason to put a thin foam strip in there?
If ain't broke don't fix it?

06-09-2005, 02:01 PM
In the L36 there is a black paper gasket between woofer and baffle, original part nr 52089 ; Can be selfmade from black "drawing paper" it is somewhat the same material as the cone.