Question for Refoamers out there

[phillyguy]

Because of the odd size of the driver in my old Infinity sub, the dealer could not find me a perfect match for a foam surround. Consequently, I will have to cut a bigger one and overlap the foam surround. I have about a 3/4" overlap, and looks like it will glue flat nicely. Question is:

At the splice, do I just glue the flat over the cone and the flat over speaker frame, and leave the "hump" unglued? Or do I just glue the lap splice entirely?

If it helps, this is a sealed sub. I was concerned if I glued the lap entirely, I would create a stiff spot on the surround and cause the edge of the cone to get hung up. Am I worrying about nothing? Any advice would be appreciated.

Thanks!

[karl k]

I've never considered if the surround kit wouldn't fit. While I've had no experience at replacing surrounds, I have fixed my share of tears in the surround and I see no reason why this won't work. I would trim the excess 3/4" from one of the ends so as to provide a "butt" joint in the surround instead of a "lap" joint. A very straight cut is important if you are to keep the circular shape intact when joining the ends. Go ahead and begin glueing the surround to the frame/cone only with the glue provided until you've gone around the whole driver. Now after the glue has set-up for a bit take a small(very small) dab of RTV Black(common auto engine gasket adhesive) on your finger and smear on the underneath side of the surround at the splice. You may have to place another finger on the top side for support while you apply adhesive underneath. You can also use some scotch tape on the top of the splice(under the finger) to help prevent the adhesive from "bleeding" through. Let set for a couple hours and install driver. Should reach full strength after 6-8hrs. The adhesive will work on both foam and rubber and provide a very flexable joint/seal although with foam, the amount of pressure should be a little greater to "embed" the adhesive into the pores of the foam. I recommend RTV because it tends to be more flexable than caulk whether in silicone or latex. In the scheme of things, the glue rigidity you are worried about probably won't mean a thing unless you get carried away with the glue but keep in mind, the more rigid the glue on "high excursion" units, the greater the risk of de-lamination or joint fatigue.

Others with more experience in surround replacement may have other ideas.

[pelly3s]

the best option is to order the proper surround for the driver and do it the right way. if the right glue is used it will not create a stiff spot. What size is the cone? Infinity probably sells the right one

[phillyguy]

Thanks for the replies! I never had to do a lap before, so I was wondering if others had run into this.

Like I said, because of the odd size of the speaker frame (10-3/4"), and the diameter of the cone (8-1/4"), the dealer (winstonorgan.com) could not match up an exact match for the surround. I used them in the past when I fixed an old pair of Mission 707's and they were very concientious (sp?) about choosing the right surround. The surround they sent was a perfect match for the width between the frame and the edge of cone, but the diameter was off. I ended going with a 1/4" lap splice, with a thin line of glue to seal it off. Even though the surround was not a perfect match, it laid down perfectly flat, just like previous refoams I have done without a splice. Since I had cut out the center cap, and shimmed voicecoil, alignment was not a problem, and after setting overnight, the coil was aligned perfectly, with no rubbing. The driver is not high excursion, so hopefully the lap will hold up. I tested a glued lap with some left over cuts I had, and they were tough to pull apart, be still pretty flexible. I think it will hold up well, if not I will refoam amy try the butt splice route with RTV Black. I think that would perform well too.

I tested the sub briefly tonight, and it is already a big improvement over the torn surround. I will give it a little harder workout tomorrow but it looks like it should hold up and perform well. The sub will be relegated to another room, once I purchase a new set of HT speakers, likely Kef or Energy.

BTW, Infinity is totally useless for parts on their older stuff, they do not carry anything anymore. I tried to just buy a new driver, or even a recommended alternate driver, but nothing was in stock anymore. I will say they were very helpful answering all of my questions, and did try to provide me with some specs for the built in amp, but they could not tell me anymore about the driver, other than it is 2 ohms with high efficiency.

[karl k]

Good deal, glad it worked!