Forte 12 inch passive buzzing

[Badco67]

I have a set of original Fortes and the problem I have is one of the passives buzzes and sounds like a blown out speaker.
It's been switched from speaker to speaker with no difference.
I've gone over it with a fine tooth comb and can find no flaws in it.
Any help or ideas why would be much appriciated.

Thanks, Bill

 

[4-2-7]

Rotate it 180 degrees

 

[mhardy6647]

screws all tight? (check all drivers for this -- and be on the alert for stripped screws)

BIG CAVEAT:
I don't know anything about the construction of the PR in the Forte...

but it is possible that it's delaminating?
Polk used some 12" PRs in the late 70s/early 80s with a foam front surface that hasn't aged well.

Also, I know that the mass loading of some PRs (albeit perhaps only those made for the DIY market?) is tuned via bolts or weights screwed onto a threaded stud. Anything like that on the Forte PR.

Is the suspension foam? If so, is it deteriorated?

EDIT: OK looks like simple paper cone... have you (the OP) tried gentle fingertip pressure to see if the buzzing can be mitigated? Something must be loose if there's buzzing, I would think. Might it be the dustcap?

 

[Badco67]

screws all tight? (check all drivers for this -- and be on the alert for stripped screws)

BIG CAVEAT:
I don't know anything about the construction of the PR in the Forte...

but it is possible that it's delaminating?
Polk used some 12" PRs in the late 70s/early 80s with a foam front surface that hasn't aged well.

Also, I know that the mass loading of some PRs (albeit perhaps only those made for the DIY market?) is tuned via bolts or weights screwed onto a threaded stud. Anything like that on the Forte PR.

When comparing it to the other passive there is no difference and that's what's making me crazy.

 

[mhardy6647]

When comparing it to the other passive there is no difference and that's what's making me crazy.

Even gently pressing on various parts of the moving cone (e.g., around the surround) with your fingetips?

Did you see this?
https://community.klipsch.com/index.php?/topic/43954-forte-ii-passive-repair-not-a-tear/

 

[Badco67]

I wonder if the KG4 passive would work in the Forte? Anybody know or ever tried this?

 

[Jenkster]

A loose dust cap, round piece in the center, will cause the passive to buzz.

 

[Jenkster]

If that’s the problem, some Aleene’s Tacky Glue will fix it up. You can find it in fabric stores or, of course, Amazon.

 

[Speedbump71]

I posted in your other thread too. Klipsch put a couple metal slugs potted in glue in the center of the cone where the voice coil would usually be for weight. If you can't find it anywhere else, it may be that those two slugs are buzzing against each other. I think there was another AKer that had that issue. Tap on the back of the black paper covered slug on the passive from the back of the basket and see if you can hear it rattle/resonate.

 

[Badco67]

I posted in your other thread too. Klipsch put a couple metal slugs potted in glue in the center of the cone where the voice coil would usually be for weight. If you can't find it anywhere else, it may be that those two slugs are buzzing against each other. I think there was another AKer that had that issue. Tap on the back of the black paper covered slug on the passive from the back of the basket and see if you can hear it rattle/resonate.

Thanks, Speedbump. I did see your other reply. I think this may be the problem as it does seem to rattle when you tap on it.
My question is how to get the dustcap off without damage?

 

[Jenkster]

Thanks, Speedbump. I did see your other reply. I think this may be the problem as it does seem to rattle when you tap on it.
My question is how to get the dustcap off without damage?

Has some of the dust cap come unglued or is it still intact? If not, I think the only way to remove it is to use an exacto knife or something similar to cut it. That is what I did with a loose dust cap on a Forte’ that was buzzing like an alarm clock. I got a replacement dust cap from I believe Parts Express. That was quite a few years ago so, before you do anything, you may want to contact member GordonW who repairs speakers.

Good luck,

Mark

 

[Badco67]

Has some of the dust cap come unglued or is it still intact? If not, I think the only way to remove it is to use an exacto knife or something similar to cut it. That is what I did with a loose dust cap on a Forte’ that was buzzing like an alarm clock. I got a replacement dust cap from I believe Parts Express. That was quite a few years ago so, before you do anything, you may want to contact member GordonW who repairs speakers.

Good luck,

Mark

Thanks Mark