Back of KG 4.2 Vibrates unless held with pressure

[biver]

Hello all,

 

I have a KG 4.2 that has vibration coming from the back of the cabinet with any amount of bass.  If I hold my hand there and push in slightly, it stops.  

 

Suggestions for how fix this permanently?

Edited February 21, 2020 by biver
Tags and Spelling

[Peter P.]

Remove the drivers from the front baffle to gain access to the inside of the cabinet. A flashlight and a small inspection mirror will help. Squirt wood glue into the seams where side panels meet the back panel. If you want, you can buy a couple of those cheap ratcheting straps to hold the cabinet tight while the glue cures. These straps should come with accessory metal corners to hold things square and protect the corners while the glue cures. You may have to glue only one edge at a time and position the glued edge so gravity draws the glue into the gap. Think of the speaker sitting like the letter "V" while the glue dries.

 

I repaired a  bookshelf speaker and a Heresy this way and it worked fine.

[Maz4bz]

This is common for KG's.

 

Others have completely removed the rear panel by gently knocking on the inside of that rear panel all the way around the edges with a rubber mallet until it completely comes free. Then reglue once all your old glue is removed.

 

I would highly recommend some shelf or other front to rear, side to side bracing while you are at it.

 

 

Good luck!  

 

[biver]

7 hours ago, Maz4bz said:

“I would highly recommend some shelf or other front to rear, side to side bracing while you are at it.”

 

Thanks for the reply.  Would you mind elaborating more about it benefitting from additional reinforcement. Something specific related to these particular boxes?

 

[Maz4bz]

Hi Biver,

I have a nice pair of KG 5.5's that came with zero bracing so that image is of my speakers. I've never had the pleasure seeing or hearing any KG 4.2's so I am assuming that these have no bracing like mine.

 

There's quite a bit written about this out there.

 

Here's an article in Stereophile you may find of interest on the topic...

 

https://www.stereophile.com/features/806/index.html

 

JBL have a tool called an interferometer for measuring cabinet deformation. This image is lifted from their M2 page on JBL Professional...

 

 

Good luck! 

[biver]

Thanks!  Unfortunately, I think these got water damaged now that I am looking at them.  I got them for free and now I'm just trying to figure out if (because of the damage) it's going to work out well to try to fix them at all.  

 

Thanks for the additional info.

 

Cheers.

[Maz4bz]

Post some pictures of your cabinets, you're bound to get some great feedback here.

 

Cheers.

[biver]

Ok, I’ve got it all taken apart and the old glue removed.  So far, so good. What else to do during a global crisis, right?

 

Question:  What kind of glue should I be using to reattach the back panel?  
 

If you know the name of a specific glue that I can order on amazon, that would be best given the circumstances. 

 

What was there was definitely some kind of rubber or silicone. 
 

Thanks!

Edited March 18, 2020 by biver

[Maz4bz]

PVA - water soluble, non toxic, dries clear, forms a bond stronger (usually) than the timber.

 

You can't use too much. Wipe up any runs with a damp cloth.

 

Try not to clamp too tightly. You want some space for the glue to occupy. Clamping with too much force will simply squeeze out the glue leaving a weaker bond.

 

I'd lay the cabinet down over some saw horses, apply glue then drop in the board. I'd clamp with some weights like a few medium weight house bricks to gently press down the board into the glue.

 

I'd get under the cabinet and look up inside for glue runs and wipe these up as they appear. The saw horses will allow you access the interior from underneath.

 

Good luck.