Cloth Speaker Surround Rejuvenation?

[douglas234]

I have some JBL E120s on which the cloth surrounds seem to be getting stiff – at least compared to my K120, which feels as flexible as foam (the E120 surrounds are so stiff they may as well be paper). I'm looking for something I could safely apply to rejuvenate or "moisturize" them. Thinking of trying a car convertible top protectant such as 303 Aerospace or Armor All, and wondered if anyone had experience with this.

Thanks for any advice!

[BMWCCA]

Never had an E120 but I've had plenty of D130s and those "surrounds" are the same material as—and in fact are—part of the cone. Maybe the rolls in the E120 are too?? In that case they'll be whatever they will be and maybe they don't need to be softer.

[douglas234]

From what I gather here, neither speaker should have a cloth surround, but they both do, so were probably recones.

I'm also gathering that a stiffer surround enables the speaker to handle more power, but I'm using these with a 25 W tube amp, so this isn't a consideration.

If no one's tried this, perhaps I'll be the guinea pig…

[1audiohack]

Hi Douglas;

The pleated cloth surrounds on the E series cones are pretty stiff when they are new. I have some K120's on the shelf at work that I can compare them to if you are interested but that would be Tuesday before I get back. It's been a while but I am sure the K120's are not as soft as foam. Maybe yours are well worn from hard use.

E120's are great for what they were intended for. What are you using these for? What frequency range are they trying to reproduce?

Barry.

[douglas234]

Hi Douglas;

The pleated cloth surrounds on the E series cones are pretty stiff when they are new. I have some K120's on the shelf at work that I can compare them to if you are interested but that would be Tuesday before I get back. It's been a while but I am sure the K120's are not as soft as foam. Maybe yours are well worn from hard use.

E120's are great for what they were intended for. What are you using these for? What frequency range are they trying to reproduce?

Barry.

I have no idea what a "new" e120 would be like, but assume they used a cloth surround because they wanted it to be more pliable than paper. So I'm suspecting it's dried out over the years. I assume this hurts the low frequency response some, which isn't the end of the world for me, since I'm only using it for electric guitar. But if someone said, Yeah, this is how you fix that, I'd definitely try it, to get a little more low end...

Thanks,
Doug

[freddyi]

if measured resonance is way off spec - like a half octave too high, then you might try a coat of Permatex gasket goop either thinned from the first place with lacquer thinner, or brush the thinner on after a coat of Permatex - I don't know the long term safety effects of the thinner upon the adhesives but think the technique could be used to soften some doped cloth (and maybe some doped paper) surrounds. The Permatex produce I have is very red - perhaps there's an equivalent in black (?) I'm tying it right now on an LE5-2 whose fs is close to 350 and Qts ~2-2.1

[douglas234]

if measured resonance is way off spec - like a half octave too high, then you might try a coat of Permatex gasket goop either thinned from the first place with lacquer thinner, or brush the thinner on after a coat of Permatex - I don't know the long term safety effects of the thinner upon the adhesives but think the technique could be used to soften some doped cloth (and maybe some doped paper) surrounds. The Permatex produce I have is very red - perhaps there's an equivalent in black (?) I'm tying it right now on an LE5-2 whose fs is close to 350 and Qts ~2-2.1

Thanks for the suggestion, freddyi! I think I remember that stuff from doing auto repair - Permatex 80062 High Tack Gasket Sealant. It's permanently flexible, and would probably "whet" the cloth and soften it some. Let us know if it works!

Haven't worked on the E120s yet, but just bought an E140 for $50 because the guy said it had "lost its spring" and needed a recone. But there was nothing wrong with the speaker except the same thing -- surrounds so stiff the speaker could barely move. I think the speaker had been in storage -- maybe this is what happens to them when they don't get enough exercise...

[badman]

Calculate what power would lead to 80% of Xmax, and feed the driver that power as a sine at 30hz or so (assuming power handling's up to it). Cloth surrounds will generally loosen back up after a good workout, do that for a few hours and test the Fs before and after, you'll see the drop. Done this a few times.

[douglas234]

Thanks badman -- makes perfect sense. You hear so much about overworked speakers, but here we have a case of the opposite...

Calculate what power would lead to 80% of Xmax, and feed the driver that power as a sine at 30hz or so (assuming power handling's up to it). Cloth surrounds will generally loosen back up after a good workout, do that for a few hours and test the Fs before and after, you'll see the drop. Done this a few times.