KLH Model 17 Woofer Clicking

[bennattj]

Just got this beautiful pair of KLH Model 17s, restored caps (wow!) and (attempted to) re-seal surrounds. I recently started thinking I was hearing a rattling from the left and sure enough, there is.

Here is a google drive link to video showing the clicking sound at 5 Hz (right in time with the 5 Hz movement). Gently pressing on cone stops the clicking: five-hertz-clicking-compressed.mp4

I inspected the spider and it looked like it was in good shape (attached pics of all around the inside). I think the dust cap is probably not fully sealed, but seems like the sounds is coming from the surrounds (but I certainly cannot tell for certain).

I'm afraid this is some kind of voice coil rub???
Or is it just bottoming out in the video (I really don't think it is)? Which might suggest more of an air seal problem??

Any ideas on how to fix (preferably easy)?

p.s. Also looking at second pick could it be that tiny gap in the lead running along paper cone?

 

[loudnoises]

If they were mine, and I use mortite, I ephemeral see if tightening the screws differently had any effect.

Edit: posted as I was going into a concert. Ephemeral? Best typo on s long time. Should be "might".

 

[tgmartin]

I second loudnoises suggestion. The pressed steel frame could certainly get warped a bit if torqued down unevenly although the extra "roll" or "step" inside the mounting flange on these smaller woofs should provide some added resistance. Have you tried it with with the speaker out of the box entirely? Careful not to overdrive it ...

While out of the box you might tap on the frame like a bell while holding the magnet assembly to see if you can detect any mechanical rattle.

 

[bennattj]

I have not been brave enough to drive it out of the box...that's probably a good suggestion to at least rule out the "screw-job" (if you will lol). I'll give that some thought...taking it out and putting it back is a pain (as you can imagine).

 

[tgmartin]

Got to wondering if the clicking at 5Hz only happens when exceeding a certain voltage level AND if the clicking happens when feeding it any other frequency. You are feeding it a sine wave, correct? If it's non-symmetrical waveform, like clipped on the negative side, that might cause the "click" sound.

 

[bennattj]

Got to wondering if the clicking at 5Hz only happens when exceeding a certain voltage level AND if the clicking happens when feeding it any other frequency. You are feeding it a sine wave, correct? If it's non-symmetrical waveform, like clipped on the negative side, that might cause the "click" sound.

On that note, yes, it's basically audible up to about 100 Hz. Starts out as a click (low frequency) but quickly develops into a rattling distorted sound in the 60-100Hz range then clears up. I would say most importantly, I have a control in the right speaker which does not make this sound (at same level).

The more I think, while I don't think it's actually over-excursion per se, I do think this is some kind of rub going on with the surround but not sure how to address that just yet. I still am figuring out a plan to try and drive it while out of the cabinet to see what happens there.

 

[tgmartin]

You used RoyC's Magic Butyl Sauce on the surrounds, right? Is it possible that you applied enough of it so that it soaked through and is now causing it to slightly stick somewhere to the steel frame on the inside? Longshot I guess. That cloth roll seems to butt up pretty close to the frame on my Model 30s.

 

[bennattj]

Well, took it out. Same noise when out of cabinet. I still can't definitely say it's the surrounds, but that's still kind of my guess.

I've somewhat decided I'm more likely to make things worse than better. I can't 100% confirm I even hear it while music is playing (since it seems to depend on the excursion--only bass heavy tracks would really push it anyway).

FWIW I wouldn't think REW at -12 dBFS and about half volume (using a passive preamp into more amplifier than I should ever need) would cause overexcursion (and like I say--the right speaker seems fine at same level).

 

[loudnoises]

Is the spider maybe loose at some point? A stiff spider tapping on the frame maybe...

 

[bennattj]

Is the spider maybe loose at some point? A stiff spider tapping on the frame maybe...

That was one of Gemini's suggestions as well. I mean it doesn't look like it to me (again hard to tell). I have some Aleene's Original Tacky Glue in case I decide I want to take another look.

 

[bennattj]

The only real thing I found was this little spot: top left, you see a little strand of yellow hard, what I assume to be, glue (I don't think from my RoyC's goo job though--since that doesn't harden like this). I tried dabbing it with some rubbing alcohol to get it off and I think I got some of it (maybe not all), but no improvement.

I thought while driving it upside down, that pushing around the surrounds in this area had more of an effect than others: i.e. the clicking went away with less pressure on the surround in this area. This is why I thought it might have been the surrounds.

But I would stress my tests were ultimately inconclusive--like I I could make the clicking go away by pressing on the surrounds at any area, it just seemed to me to require less pressure around this area. And I couldn't really say yeah, the sound was cracking from this part of the surround (just touching that part didn't make it go away and I didn't feel a click or anything).

 

[BmWr75]

Sagging spider on the back of the cone maybe. An old trick is to remove the woofer from the cabinet, rotate it 180 degrees and reinstall. This sometimes gets rid of a voice coil rub. I’ve also had KLH 6 and 17 bottom out the woofers if played too loud.

 

[bennattj]

Sagging spider on the back of the cone maybe. An old trick is to remove the woofer from the cabinet, rotate it 180 degrees and reinstall. This sometimes gets rid of a voice coil rub. I’ve also had KLH 6 and 17 bottom out the woofers if played too loud.

Currently trying this--kind of my one hope at this point. It's been about a day, no improvement yet.

 

[bennattj]

One other suggestion from Gemini was to apply some glue and attempt to reseal the dust caps (with toothpick and careful application/pressure with Aleene's Original Tacky Glue).

Think this might be worth a try?

right speaker dust cap

left speaker dust cap

 

[tgmartin]

They look pretty good in the pics but couldn't hurt I guess.
I'm gonna have to get me some of that Aleene's as I see it mentioned often. Hobby Lobby? I didn't see it at Ace Hardware.

 

[bennattj]

They look pretty good in the pics but couldn't hurt I guess.
I'm gonna have to get me some of that Aleene's as I see it mentioned often. Hobby Lobby? I didn't see it at Ace Hardware.

I just ordered from amazon...a small amount was like $2.

 

[bennattj]

I should add, in all fairness to these, they sound amazing (and I just recently inherited a really nice sub-woofer) so I might just be nitpicking this little anomaly.

Hell it was that left speaker that blew me away on Ruby Tuesday cello part...

 

[loudnoises]

They look pretty good in the pics but couldn't hurt I guess.
I'm gonna have to get me some of that Aleene's as I see it mentioned often. Hobby Lobby? I didn't see it at Ace Hardware.

Or Joanne fabrics. Maybe even wally world.

Great product.

 

[tgmartin]

I got it at Michaels' ... Thanks for the suggestions!

 

[tgmartin]

I just got a pair of Model 20s that need caps replaced so as I was pulling the woofs I noticed that the cloth suspension on these actually rides up on the metal frame in the back in places. The cloth actually touches the frame. I recalled the clicking sound from this post and my harebrained suggestion that maybe, just maybe, the butyl treatment may have soaked through the cloth causing it to stick slightly to the frame causing a snap or click when it gets pulled away. I still think it's a longshot and most likely voice coil related but wondering if you had a chance to look into this any further. I imagine if one were to use a finger to try and separate the cloth roll from the frame in spots, WITHOUT DRIVING IT WITH A SIGNAL, it might not make the clicking sound but maybe it would reveal itself in some way. Maybe a popsicle stick or disposable plastic knife would work better to allow you to get down in there a bit without damaging anything. Hope you get a resolution to the problem! Carry On ...