Subwoofer surround question?

[mbottz]

I am refoaming a 121A woofer and need some of the forums expert help. I purchased one of Rick Cobbs new foam surrounds, and installed it using the 30 hz centering tone. I have refoamed twice and still can not get it right. I use around 10 to 20 W when centering with the test tone and think I have it, as it sounds perfect ( no rubbs). But when I reassemble into the cabinet and play music at the same level it still makes a rubbing sound. What am I missing? does it have anything to do with the mass ring? Do I need a new spider? Lets hear from the pros!! What am I missing?

Thanks in advance

MB

[duaneage]

Are you sure the mounting screws are not too tight or uneven in their tightness. Normally being good and tight is a good thing but with woofer baskets you can distort the frame and cause a rub.

[boputnam]

Are you able to run a frequency sweep through the transducer, with a low voltage drive? It may be that it doesn't rub at 30Hz, but does at something else.

Can you aurally guess what frequency that might be?
Can you be certain it is from the voicecoil?

[Robh3606]

I have had that happen with me and an Le-14A. One was a snap the other a cast iron bitch to center. On the bench it's fine as soon as you mount it, it can rub. Let gravity help. Try remounting with the rub side down. It worked for me. I have used it in my sub cabinet for 6 months now with no problems. Just lightly touch the cone to tilt in in the gap. If it's off center you should be able to see which side is the one with less clearance.

Check to make sure the tinsel leads are not hitting the cone as well.

Good Luck

Rob

[rek50]

Change the driver "Position" by rotating the cabinet. Once you find the
"No Rub" position remount the driver to suit.

[mbottz]

After many resurround attempts and much frustration I finally found why my 121A voice coil rubs after the resurround. It seems the mass ring was only glued on 1 side, Therefore when you manually moved the cone there was no rub, but when you hooked it to a music source the mass ring would start to flap and flex which distorted the voice coil to cause a rub.

Just a FYI for those of you doing resurrounds, make sure the mass ring is glued in solid.

I probally have the only driver like this, the tech which assembled the driver was probally smoking that wackey weed.


Regards

MB