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View Full Version : 2461, 2410, 2420 damping material


GRIMRIAN
12-30-2020, 10:37 AM
Folks, has anyone been experimenting with damping material in the cavity behind the diaphragm? Mine (2461, looks like some sort of plastic foam) is mostly disintegrated, and I suppose it should be replaced. But with what? And is it important? Before I begin a bunch of tests it would be good to hear what you think.

Cheers
Mr. Widget
12-30-2020, 11:14 AM
The foam in there does go bad and may get into the VC gap and cause problems. The original damping pads that JBL used in the '50s and '60s was a thick sheet of felt. It appears to last forever.

You should clean the back caps and replace the foam with new foam or you can use felt as a longer lasting alternative.


Widget
Epplerd
12-31-2020, 12:57 AM
Folks, has anyone been experimenting with damping material in the cavity behind the diaphragm? Mine (2461, looks like some sort of plastic foam) is mostly disintegrated, and I suppose it should be replaced. But with what? And is it important? Before I begin a bunch of tests it would be good to hear what you think.

Cheers
Much work has been done on phase plug design in compression drivers, but the rear cavity seems to get little mention. It's a high acoustic pressure environment and needs damping to help suppress any resonances present. Different damping materials will effect the reproduced sound in different ways. The back cover rigidity will also effect the sound. it's worth experimenting, but beware, once dismantled the diaphragm inside a compression driver is easily inadvertently damaged.
Epplerd
12-31-2020, 11:19 AM
Folks, has anyone been experimenting with damping material in the cavity behind the diaphragm? Mine (2461, looks like some sort of plastic foam) is mostly disintegrated, and I suppose it should be replaced. But with what? And is it important? Before I begin a bunch of tests it would be good to hear what you think.

Cheers
One material you might try is low density memory foam (40kg/cubic metre). I've used it in 2421A's and Tannoy HPD 315's.
macaroonie
12-31-2020, 06:58 PM
The word Tannoy can make some folks itchy around here. Be careful.

Happy new year.