JBL dampening material one wall application theory

[Wardsweb]

I would like some information on why many JBL cabinets were lined only on one parallel wall of the cabinet; i.e. the bottom, one side and the back? Why this versus many speakers that are lined on all walls.

[timc]

I guess the idea is that to have resonances in the cabinet you need two paralell surfaces. Then thick damping on one side, will provide better damping lower down in frequencies than the equeal thickness distributed on both sides. This is true if there is no room between the dampening material and the walls. If there is an airgap behind the damping material, so that the thicknes of the material and the airgap combined is equal to the total thickness of dampening material, then the difference is less.

[Mr. Widget]

It seems to me it was the fashion/theory across the board used by most manufacturers back in the '50s and '60s to apply the damping material to every other surface. It was also usually done with a much heavier cotton or wool padding... in the later '60s and into the '70s most manufacturers switched over to fiberglass and placed it on all interior surfaces except for the front baffle. Most speakers are still done this way today though some use polyester wadding or foam.

Is one way better or worse? I have no idea. I have done experiments with different materials and the material along with just how much you use does have a very real effect on the sound.


Widget