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Jim Gregory

Crack in 402 repair

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First off, you need to make sure any resin/glue is compatible with your horn composition. After that, if it would retain its shape while applying, I would try some thin carbon fiber mat and epoxy or polyester resin. On the back side, of course.

 

Bruce

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Determine the type of plastic first.  They look like ABS to me.  It patches well.  Stop drill each end first, too. 

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That looks like it should be fairly easy to repair, after you do a dry run with your clamping method and you get a little practice with your epoxy on some scrap materials. Wearing some disposable latex or nitrile gloves is recommended.

Edited by Khornukopia
If it is ABS, then use ABS cement instead of epoxy.

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1 hour ago, Marvel said:

First off, you need to make sure any resin/glue is compatible with your horn composition.

Can anyone here help in identifying the composition material of the 1st generation 402 and a compatible resin/glue. 

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You can try this on an edge, but I believe what you're working with is ABS (a thermoplastic with glass transition temperature of 105°C/221°F), and it can be dissolved using acetone.  Here's a thread where someone tried using acetone to dissolve ABS and mix into a paste to dab on the crack:  https://www.whitearmor.net/forum/topic/37513-how-to-fix-cracks-in-abs/

 

Chris

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Thank You to everyone for the great advice and pointing me in the right direction. I will report back on my final process with pictures. 

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4 hours ago, Marvel said:

First off, you need to make sure any resin/glue is compatible with your horn composition.

True, you could try it on one of the fins/brace on the back.

 

I was told there were 2 or maby 3 different materials used for that, 2 positively. 

One of the two was glass infused, I don't know if the other part of the Resin or whatever it is the horn is made of was the same or not but some have glass infused in the plastic.

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2 minutes ago, dtel said:
5 hours ago, Marvel said:

First off, you need to make sure any resin/glue is compatible with your horn composition.

True, you could try it on one of the fins/brace on the back.

Great idea dtel, 

I will definitely do my trial experiments on one of the fins on the back. 

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Should be fine, just try a LITTLE somewhere where it is not a problem if it were make the horn soft or something crazy, should be fine, it's what I would do. And I would also do what your trying, to fix a cracked horn, why not.

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2 hours ago, Jim Gregory said:

Can anyone here help in identifying the composition material of the 1st generation 402 and a compatible resin/glue. 

The first gen horn material is some sort of plastic that's very porous, brittle and as already stated, very sensitive to heat. Standard epoxy glues work fine to bond cracks and does not dissolve this base material if you can manage to get it into the cracks. Thin CA or cyanoacrylate glue works wonderfully in the hairline cracks where epoxy cannot be forced in. These glues are easily available at any hobby shop or woodworking supply store. Besides the glues, standard body shop methods and materials work well to refinish the surface of these horns. An experienced body shop man would make the job look too easy.  

 

But, if you go through all the work and expense to repair the cracks and resurface the first generation horns,  you still have a defective horn that's susceptible to heat warping because of the poor choice in plastic used in the original manufacturing process. Not to say repairing isn't an option. If you have the time, tools, know-how, experience, materials and willingness, then by all means go ahead and repair them. As long as you're at it, the entire outside of the horn could be covered in laminated fiberglass resin and cloth to prevent further warping.  It's sorta like the DIY'er that devoted many months to restore a 1970's Chrysler. After all the work, time and expense - all he has is still is an old Chrysler that was never worthy of all the time and expense put into the restoration job. People also have different standards of aesthetics. I personally can't have a set of warped K-402's in my listening room, the rough demeanor would bother me. Heck, these horns in brand new condition generally rub the wife the wrong way just because of the outlandish proportions. Add a horn surface that's all warped out of shape and I'm pretty sure most married men don't have spouses that are that understanding.  I wouldn't mind a set in the workshop, except it gets much too warm in there. Another option is to repair the cracks with epoxy and build a nice plywood cabinet with a grill and forget about it.

 

There's a third option! Did you know that a sales rep of Klipsch Inc. will sell you a set of brand new replacement horns for a very reasonable cost if your horns are really 1st generation? The sales are Roy Delgado approved, he took full responsibility for the defective 1st generation horns that I purchased (at top dollar) from an unscrupulous long time forum member. So I would imagine that you too can purchase just the horns, no drivers or stands at a considerable discount.   

 

 

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1 hour ago, DMH said:

here's a third option! Did you know that a sales rep of Klipsch Inc. will sell you a set of brand new replacement horns for a very reasonable cost if your horns are really 1st generation?

DMH

3rd option is worth looking into. Would you IM me the contact information for this option. 

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On 9/10/2019 at 9:45 PM, DMH said:

There's a third option! Did you know that a sales rep of Klipsch Inc. will sell you a set of brand new replacement horns for a very reasonable cost if your horns are really 1st generation? The sales are Roy Delgado approved, he took full responsibility for the defective 1st generation horns that I purchased (at top dollar) from an unscrupulous long time forum member. So I would imagine that you too can purchase just the horns, no drivers or stands at a considerable discount.   

Roy is a stand up guy and took care of a legacy problem I had too and this was on drivers from the 90's. They failed because of a manufacturing defect and he stood behind it.

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How do you identify which version of 402 you have?  I bought mine used in 2017, but I think the seller had them for a year or less.  That’s just a guess, though.  It would be good to be sure.

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  1. The first gen horns have metal throats/flanges and have dull mat finishes (and crack/warp easily if exposed to direct, hot sunlight, etc.)
  2. the second gen horns are 25 pounds weight and are darker and shinier looking
  3. the 3rd gen horns weigh 15 pounds and are grayer looking with a mat finish
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Now I'm wishing I had weighed mine before I bolted on the drivers and bases.  However, the dark shiny finish is a good clue.  They look very much like my non-mumps K510s.

 

Thanks, Chris!

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On 10/9/2019 at 4:30 AM, Islander said:

 However, the dark shiny finish is a good clue.

Same here, thinking it's the second version, either way I have had no problems with them.

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5 hours ago, dtel said:

Same here, thinking it's the second version, either way I have had no problems with them.

 

No problems with mine, either.  Sometimes I wonder about painting them, though, because the ground-off molding lines, with the look of irregularly edged stripes across the backs of the horns, look like they just came out of the molds and were given a quick smoothing grind.  Then, before they went to the finishing area, they were pulled aside and sold.  That's my impression of the looks of both the 510 and 402 horns.  Luckily, the front sides look better, and they do sound great.

 

When using nuts and bolts on a plastic object, like these horns, instead of using the usual split washers that require the nuts to be tightened until the washers are squeezed flat, I like to use Nyloc nuts, the ones with the nylon inserts in their tops.  The nylon (which I've seen in white, black, and blue) is smooth when they're new, but when they're turned onto a bolt, the threads of the bolt press into the nylon, increasing the contact surface and the friction.  This works to keep them from unscrewing.  In typical metal-to-metal applications, the nuts and bolts are tightened normally, but in applications where not much clamping force is required, like securing plastic horns to their metal or plastic bases, you don't need to tighten them nearly as much.  The only limitations are that they can only be re-used a few times (always buy extras), and they can't be used in hot applications, like on exhaust manifolds.

 

When securing my horns, the Nyloc nuts allow me to snug up the nuts not much more than finger tight, and still know that they won't come loose, in spite of whatever vibration they may experience.  After 11 years, the nuts on my 510 horns that hold them onto their bases are still tight.

 

The reason for using nuts that stay snug even when they're not that tight is to almost eliminate any chance of cracking or deforming the plastic.  Cracking can easily happen if nuts and bolts are tightened too much on plastic pieces.  As well, the relatively soft (softer than steel) plastic can deform under the pressure, causing the nuts to come loose over time, especially if vibration is added, like with machinery running on or near the piece.  There's much less vibration in an audio application, but it's still there, so it should be considered.

 

I didn't think a simple nut recommendation would run that long, but there you go.  And people think that mechanics "work with their hands", without much thinking...

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