friction causing "farting" in ADS L780/2 woofer?

[warriorofmetal]

my grandparents gave me a pair of ADS L780/2 speakers, and there's a problem with the woofer in one of them. i'm a fairly technically minded person, so my grandparents told me i could keep or sell these or whatever if i can fix them up....

anyway, after pulling both woofers out of their cabinets, i have discovered that there is something in one of them that's creating friction, so that when the speaker cone moves, this friction translates into a very "farty" sound coming out of the speaker. is there any easy way to fix this? i'm hoping it's just something like a part being dirty, and that all i have to do is get into it and clean it out....but if that's the case, how exactly would i go about doing that?

thanks for any info you can give me.

[romanbednarek]

Re: friction causing "farting" in ADS L780/2 woofe


> my grandparents gave me a pair of ADS L780/2
> speakers, and there's a problem with the
> woofer in one of them. i'm a fairly
> technically minded person, so my
> grandparents told me i could keep or sell
> these or whatever if i can fix them up....

> anyway, after pulling both woofers out of
> their cabinets, i have discovered that there
> is something in one of them that's creating
> friction, so that when the speaker cone
> moves, this friction translates into a very
> "farty" sound coming out of the
> speaker. is there any easy way to fix this?
> i'm hoping it's just something like a part
> being dirty, and that all i have to do is
> get into it and clean it out....but if
> that's the case, how exactly would i go
> about doing that?

> thanks for any info you can give me.

One "worst case scenario" possibility is that the voice coil is deformed due to excessive overheating over time. This would cause it to rub and I don't know of an easy way to fix this.

My dad had a trick that he used for his Dynaco A25 speakers when this happened to one of the drivers. He cut off the dustcap, pulled the cone forward and used a spoon on the inside of the voice coil to move it away from the pole piece. This is very tricky to get right without damaging the speaker. The trick is to only "smooth out" the parts of the voice coil that might be rubbing. If you push too far it will mess up the driver and response.

The "easy fix" scenario is if there is some particles in the speaker which can be carefully vacuumed out.

Hope that helps and good luck.

[Paul O]

Re: friction causing "farting" in ADS L780/2 woofe


Sounds like a blown driver. A quick test is to press on the cone of the speaker and compare it to the other good working driver. If it moves easier then the suspension is fatiqued, and/or the voice coil is partially shorted. If you have a multimeter measure the drivers resistance. If the bad driver measures lower then this confirms the above. Best course of action is a recone, or replacement.

[warriorofmetal]

Re: friction causing "farting" in ADS L780/2 woofe


> Sounds like a blown driver. A quick test is
> to press on the cone of the speaker and
> compare it to the other good working driver.
> If it moves easier then the suspension is
> fatiqued, and/or the voice coil is partially
> shorted. If you have a multimeter measure
> the drivers resistance. If the bad driver
> measures lower then this confirms the above.
> Best course of action is a recone, or
> replacement.

alright, i'll check them both and see what it comes out to.....the hand test was how i discovered what the problem actually was though.

[Paul O]

Re: friction causing "farting" in ADS L780/2 woofe


BTW...The only thing that could make a scrubbing noise when the cone is moved is the voice coil rubbing in the gap. Lots of things could cause this like a shifted magnet pinching the coil from 1 side, a voice coil that has partially unwound from overdriving or maybe age(glue has deteriorated) or again the suspension is weak and the cone is sagging unevenly.

[warriorofmetal]

Re: friction causing "farting" in ADS L780/2 woofe


> BTW...The only thing that could make a
> scrubbing noise when the cone is moved is
> the voice coil rubbing in the gap. Lots of
> things could cause this like a shifted
> magnet pinching the coil from 1 side, a
> voice coil that has partially unwound from
> overdriving or maybe age(glue has
> deteriorated) or again the suspension is
> weak and the cone is sagging unevenly.

what kind of repair cost am i likely looking at?

[irishbreed]

Re: friction causing "farting" in ADS L780/2 woofe


> what kind of repair cost am i likely looking
> at?
If you are good with your hands, then not to bad. But if your not, than i would get good. You can google speaker repair and theres several place to order cones from, might think about replacing the cone, the surrounds, and get a new dust cover shouldnt take more than an hour. But if one needs it than sout for the sky's and do both woofers you'll be happier with the results.

[warriorofmetal]

Re: friction causing "farting" in ADS L780/2 woofe


> If you are good with your hands, then not to
> bad. But if your not, than i would get good.
> You can google speaker repair and theres
> several place to order cones from, might
> think about replacing the cone, the
> surrounds, and get a new dust cover shouldnt
> take more than an hour. But if one needs it
> than sout for the sky's and do both woofers
> you'll be happier with the results.

if there's no visible deterioration of the surrounds, how do i know that that will fix my problem?

[irishbreed]

Re: friction causing "farting" in ADS L780/2 woofe


> if there's no visible deterioration of the
> surrounds, how do i know that that will fix
> my problem?
No, not just talking about the surrounds. But some people when changing out the cone which has the voicecoil connected, would forget to order new surrounds. The bottom line is that you voice coil has been damaged and needs to be replaced. You can try to fix it with a spoon or what have you. But that is just not practical, it may work for a while. But if you change the bad one out you need to do both of them so it will be uniformed. Just my .02