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Stripped threads on a K400 horn


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I just realized my K55M was basically just sitting in there loosely. After taking the driver out I confirmed the threads are indeed stripped. Anybody ever have this issue? If so we’re you able to fix it and how?

 

Thanks in advance for any input or suggestions.

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33 minutes ago, grindstone said:

Yeah wash that thing out well & find somebody with the right tap and chase those threads first.  All they need to do is seal against a gasket and really about 2.5 threads do the lion's share of the holding in most applications. 

Funny that you mention the gasket and the 2&1/2 threads because I just now took the horn out, removed the 1/16” gasket and the driver fits snug without it. Put the gasket back in and driver won’t hold. I found a machine shop nearby so I’m taking it there today to see what they can do. 

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Since the driver will hold tight without the 1/16” gasket I figured maybe I could try using a thinner “gasket” to see if it would hold. Well, I ended up applying thin strips of electrical tape to the top of the driver edge where it meets the horns and sure enough it fit snug and the tape is acting as a gasket albeit a very thin and improper one. My question is, would this do the trick as far as damping any vibrations from driver to horn? My guess is yes but I’m also thinking that since the electrical tape is very thin it might transmit some or a lot of vibration.

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Edited by gilligan
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4 minutes ago, gilligan said:

Since the driver will hold tight without the 1/16” gasket I figured maybe I could try using a thinner “gasket” to see if it would hold. Well, I ended up applying thin strips of electrical tape to the top of the driver edge where it meets the horns and sure enough it fit snug and the tape is acting as a gasket albeit a very thin and improper one. My question is, would this do the trick as far as damping any vibrations from driver to horn? My guess is yes but I’m also thinking that since the electrical tape is very thin it might transmit some or a lot of vibration.

 how does it sound ?  as long as it sounds good , you've done a temporary repair

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Yeah it's not vibrations but air-tightness and proper distance to the throat that are your goals if you're being picky.  Tape'll be fine, too, but the question becomes how did they get like that and what does your driver look like, too?

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I used a set of driver in some k-400s and had no gaskets at all. the face of the drivers were tight against the horn and it was a lot cleaner than the funky gasket that had been in the horns.

 

The teflon plumbers tape would work fine and is cheap. Lowes, HD, ACE would all probably carry it.

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1 hour ago, grindstone said:

Yeah it's not vibrations but air-tightness and proper distance to the throat that are your goals if you're being picky.  Tape'll be fine, too, but the question becomes how did they get like that and what does your driver look like, too?

The threads on the driver look pretty sharp. As for the driver itself, it’s very oxidized but still working

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58 minutes ago, Marvel said:

I used a set of driver in some k-400s and had no gaskets at all. the face of the drivers were tight against the horn and it was a lot cleaner than the funky gasket that had been in the horns.

 

The teflon plumbers tape would work fine and is cheap. Lowes, HD, ACE would all probably carry it.

Tried the plumbers tape and it didn’t help. I will try just screwing it in there. The face of the driver is pretty flat and so is the surface where the horn meets it so I’ll give it a shot.

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I'm a machinist and that's not a simple job. I do know a few relevant things that could be helpful.  Those drivers are 1-3/8"-18. Good luck finding a helicoil. It was bottom tapped, either at the foundry or by Klipsch, and probably with the face of the tap ground flat to get threads near the bottom. 

 The threads in the K400 are sloppy on my pair. Your best bet is find a replacement or build it up with weld or Devcon and re-tap. The suggestion to use tape isn't a bad one, but it didn't work because tape wrapped around the external thread just goes in the root of the external thread. You need to build up the minor diameter of the internal thread, or the crest of the external thread. I would try something along the lines of a thin plastic shim or foil instead of the Teflon tape.

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