quad esl57 dustcovers losing tension

[malthuse]

I rebuilt my quads recently and the dust covers for the bass panels keeps losing tension. I can tell because the sound starts to get boomy and finally I can hear rustling and the sound of them crackling with certain frequencies. I took the grills off and reshrunk them and they are back to perfect sound again.

Is this common? Will it eventually go away after a few times as the mylar loses it's ability to shrink?

I used 12 micron mylar heat shrinked. The trebles aren't a problem, they were rebuilt by quads unlimited.

 

[chinsettawong]

Dust covers loosing tension shouldn't affect the sound though.

 

[malthuse]

I don't know about that. When I play music and watch the dist covers shaking it's hard to imagine the loose tension hasn't affected the sound. They seem to absorb sound energy.

 

[golfnut]

Actually, the dust covers should be as loose as practical. So long as they don't flop about and cause problems with extraneous noise, all will be well.

At low frequencies, where the gap between the diaphragm and dust cover is small compared to the wavelength, the diaphragm and dust cover move together. Also, any restoring force on the dust cover will be transmitted through the air gap and applied to the diaphragm. That is, the tension in the dustcovers will add to the diaphragm tension and raise the resonant frequency. This effect is minimised by ensuring the dust cover tension is as low as practical.

 

[WrineX]

12 micron 🙂 that's funny , 12 micron is not exactly acoustical transparent🙂

i wonder if you heat the dust cover or one of the panels.

 

[malthuse]

it's hilarious, especially when you consider the originals were 12 micron, although it was Saran not Mylar.