Did I botch a refoam job?

[doyall]

I am partially through a refoam on a LE8T-1 from my Aquarius IV's. (That Lansaloy stuff sure is hard to get off!) Anyway, when attaching the new foam to the cone I managed not to get the cone centered in the foam. (The cone diameter is a bit smaller than the inside edge of the foam roll diameter. Foams came from Rick Cobb. They say JBL LE8 on the back.) The greatest distance from roll to cone is apx. 2/32 inch. The smallest distance from roll to cone is a tad less than 1/32 inch. The attached picture may show the situation. Should I put a new foam on or is it OK as is?

[speakerdave]

Were you running the 30 Hz signal through it while positioning that seam? If you skipped that part . . . .

Even if it does not rub now, it is possible the voice coil is canted and there is some tension between the spider and the surround. The cause may be that the spider had asymetrically sagged, which could have happened if the lansaloy was completely separated for most or all of the circumference for a long period of time, since in that speaker these drivers lie on their backs. This can sometimes be perceived by eyeballing the spider.

The distances you mention combined with the geometry of the piece suggest that it might be all right, at least for awhile. Since this speaker is not reconable whatever you do next do carefully. If you refoam, after you get the new/old foam off, see if you can see whether the edge of the cone is tilted. Since the distances would be greater at the cone edge, a problem with the spider may be easier to see there. If so the spider is tilted, and you may need to resort to corrective measures for that. That would involve removing the dustcap and using spacers for the voice coil combined with propping up the cone with pieces of something (stryofoam) between the cone and the struts. You might also look for details about RobH's heat treatment for the spider. This is a dicey business by no means guaranteed of success. But, if you don't, then a second refoam could well turn out the same way.

I would try running signal through it to see if it is hitting. If not, I would use it the way it is. Although trouble could emerge later, it also might not.

[doyall]

I have not yet glued the surround to the frame so there has been no need to send a signal through. These transducers were in excellent shape before I got a hold of them. Lansaloy wasn't cracked the first bit. Just a little stiff. (Now wishing I had done the brake fluid treatment.) I doubt they were ever played much. Came from an estate. Spider doesn't appear to my untrained eye to be deformed, sagging, etc.

I guess all I can do is finish the job and see what happens.

[speakerdave]

I have not yet glued the surround to the frame so there has been no need to send a signal through. These transducers were in excellent shape before I got a hold of them. Lansaloy wasn't cracked the first bit. Just a little stiff. (Now wishing I had done the brake fluid treatment.) I doubt they were ever played much. Came from an estate. Spider doesn't appear to my untrained eye to be deformed, sagging, etc.

I guess all I can do is finish the job and see what happens.

Done for a few seconds, it might have helped wiggle everything into place.

I think you did the right thing skipping the brake fluid. I've experimented with some LE10 cones that were already wrecked. It is a tedious and time-consuming process. It is very easy to get some excess fluid on there, and it soaks into the cone edge (there is some question about glue sticking to that if you then decide to refoam). Then six months or a year later it needs to be done again. I would never try it on irreplaceable cones.

If you really think the off centeredness is only your flub, then it would probably be best to redo the foam.

[JBL 4645]

I also run a series of size wave tests when repairing one of the JBL control 5 with a rubber surround over the foam type and its still in place after 3 years.

[brutal]

My concern with an off-center surround would be the stresses placed on the cone by the surround at excursion would tend to cant the cone/VC assembly, possibly causing VC rubbing at extreme excursion. On that driver, and with that 1/32" of off-center, it may not be enough to cause a problem. I think proceeding with a careful eye and testing is the best course for you now.

[boputnam]

... when attaching the new foam to the cone I managed not to get the cone centered in the foam. I have noticed this, myself. It may or may not be a problem.

Next time, before gluing, see how things line-up "dry". If it does not align, you cannot fix it with the surround.

The biggest issue is whether the voice coil rubs. If it does not, you should be OK. As Dave suggests, if you can, sweep the transducer with a frequency generator at low voltage drive. Alternatively, if Rick's kit contained a 30Hz test tone, use that - again, at low gain. Listen for physical rubbing of the voice coil (do not be distracted by the quiet fluttering of the cone in this free-air setting). You cannot test for rubbing with your bare hands - do not do this as you can damage the voice coil.

[4343]

I just finished installing a pair of LE111's today, been breaking in the foam on my "new" L110's all afternoon.:bouncy::applaud:That's the good news, the "new" L166's got held up a while when the first 122A would not stop rubbing no matter what I did to the surround. I had to lift the foam off the still wet glue on the basket, then remove the dome to shim the coil. That's when I noticed the spider was offset by the shimming, and the new foam was folding up on one side of the basket...:blink: I had to remove the whole cone assy to center the magnet on the basket.

It may be that when you were gluing the foam to the cone you let the foam center into the basket, rather than keeping it centered on the cone. Having done this before, I always make sure the cone is my reference for the first gluing, and then the test tone is reference for the second...

Personally, I like to shim whenever possible.

Best thing to do is Like speakerdave and Bo both said: try the tone to see if it can be centered. Good Luck! Oh, and if the coil does not rub at low to medium levels, but the cone is a little canted, you may want to ignore my .sig and only use it at moderate levels...

P.S. I took another look at your photo, it does appear that there is plenty of space around the foam, more on the bottom than the top, so I think you could be OK. My LE111's both had the foam right up against the basket all around, yours appear to have a slightly smaller diameter.