AR-4x - cabinet repair

[swayzeeee]

Recently, I've found repairing, restoring and most of all listening to vintage AR and KLH speakers to be a very addictive hobby. ? Anyways, a couple days ago, I was lucky enough to come across a pair of AR-4x for little more than lunch money. All drivers are original and working, the grills are in great condition. The cabinets for the most part are in pretty good condition too, except for one big issue: the diagonal cabinet joints where the side boards connect to the top have started to split or come apart at the edges so that there is now a gap of about 1mm on one joint and about 0.5mm on the other. They seem to have been stored in a basement or garage for many years, stacked upside down so that the top of the speaker in question was sitting on the ground soaking up moisture all that time. Since it's the top of the speaker, it's pretty unsightly.

Has anyone encountered a situation like this? Any thoughts on how to address this issue? My first idea was to  use some kind of wood filler in the gap...

  

[JKent]

Nice speakers! With a little TLC they'll be good as new.

Glenn is the expert on this but here's his method as I understand it:

1. Dig out all of the loose wood particles. When the cabinet got wet those particles expanded and are now too big.
2. Squirt some glue in the joints. Wood glue or hide glue are good choices. If you've dug out too much you can thicken the glue with some fine sawdust (like from a sander's dist collector).
3. Use long bar clamps or pipe clamps (Pony clamps) with blocks of wood to squeeze the corners shut. Put paper or wax paper between the blocks and the cabinet so you don't glue those together ?

For corner bashes and gouges, I use John O'Hanlon's method: Clear epoxy mixed with #22 Mixol to make a brown liquid epoxy. Use masking tape to form dams as needed.

Hope this helps. Maybe Glenn will add his comments (and if so, listen to him. I've seen his restorations up close and they are beautiful).

-Kent

[GD70]

Thanks Kent!

Hey swayzee! 

Kents advice is very good. The key is to remove a lot of the swelled particle board allowing the joints to be brought back together. 

This is not for the faint of heart. You'll need a small, thin bladed hand saw, and an Exacto knive and #11 blades. The saw is used to remove the bulk of the swelled material. You may need to go down to the lowest point of the joints. Once you've removed a sufficient amount, test with the clamps and see of the corners can be brought back together. It may take more material removal to achieve this. If you get to a point where you can get the corners almost together and no further, then it's time to start gluing. With this type of repair, I use ZPoxy finishing resin. It's a very thin 2 part epoxy that's easily absorbed by the particle board. I apply it into the gap with a flat blade screw driver, letting it drip into the gap. After 15-20 minutes,  I add walnut sanding dust to add some color, it will be darker than the veneer, fold  a piece of wax paper to make a square edge to form the corner. Clamp and have paper towels handy to immediately wipe way any epoxy that squeezes out when tightening the clamps. Place the folded wax paper and press down along the joint. Once cured, unclamp and  remove the wax paper. Carefully block sand the corner smooth with 320 grit and be careful to not sand through the veneer along the joint.

Repeat the process for the other separated joints.

Glenn

[swayzeeee]

Kent and Glenn,

Thanks for the guidance! To make sure I understand everything... I let the Zpoxy sit in the gap for 15-20 minutes before clamping, right. I'm not sure I follow the part about the folded wax paper... after clamping, I press that along the joint to bring the edges together? Why wax paper?

Thanks again

Robert

[JKent]

1 hour ago, swayzeeee said:

Why wax paper?

When you clamp the speakers you want to use long bar clamps or pipe clamps with wood blocks. The wood blocks help disteibut the force evenly and prevent the metal clamps from gouging the speaker's veneer. You put wax paper between the speaker and the wood blocks because when you tighten the clamps glue will squeeze out and you don't want to epoxy the wood blocks to the speaker.

The 1st shot shows an EMI cabinet I tried to force together without digging out the particles as Glenn describes. It doesn't work. The second shot shows the use of blocks and wax paper.

-Kent

[JKent]

1 hour ago, swayzeeee said:

I let the Zpoxy sit in the gap for 15-20 minutes before clamping, right.

Just make sure it's not the "5-minute" epoxy! Glenn recommended the Finishing Resin https://www.amazon.com/Pacer-Technology-Zap-Finishing-Adhesives/dp/B0084UAPMG/ref=sr_1_6?keywords=z-poxy&qid=1555942939&s=gateway&sr=8-6 It has a 20-30 minute working time, so I wouldn't wait more than 15 minutes to add the sanding dust.

Actually, I'll defer to Glenn but I mix the sanding dust in first. That way you can control the mix. It does thicken it, so it will fill in any voids left by digging out the garbage. Or color it with Mixol #22 and just use more epoxy. https://www.woodcraft.com/products/mixol-tint-tobacco-22-20-ml

-Kent

[swayzeeee]

Thanks, Kent. Those pictures are just what I needed to visualize the job. Looking forward to the weekend and getting to work on this...

[GD70]

Take a look at my thread on AK when you get a chance. This was a restoration project for a set of 1967 3a's. They wer pretty beat up, but the end results were pretty good, and the client was very happy.

BTW, Chris rebuilt the tweeters for this project.

Post#7 shows the wax paper being used to help make a mold for the corners.

I'd post the pics here, but I've use up all my space here with pics in other threads.

Cheers, Glenn

https://audiokarma.org/forums/index.php?threads/new-ar-3a-restoration-project.795357/

[GD70]

On April 22, 2019 at 10:20 AM, JKent said:

Just make sure it's not the "5-minute" epoxy! Glenn recommended the Finishing Resin https://www.amazon.com/Pacer-Technology-Zap-Finishing-Adhesives/dp/B0084UAPMG/ref=sr_1_6?keywords=z-poxy&qid=1555942939&s=gateway&sr=8-6 It has a 20-30 minute working time, so I wouldn't wait more than 15 minutes to add the sanding dust.

Actually, I'll defer to Glenn but I mix the sanding dust in first. That way you can control the mix. It does thicken it, so it will fill in any voids left by digging out the garbage. Or color it with Mixol #22 and just use more epoxy. https://www.woodcraft.com/products/mixol-tint-tobacco-22-20-ml

-Kent

Kent,

You are correct. First, let the ZPoxy seep into the gap. I dribble it in with a small flat blade screw driver tip. Keep adding it for 10-15 minutes or so. Wipe away any ZPoxy that  is on the surrounding veneer surfaces. You want as little as possible on the veneer because you don't want it preventing the Danish oil from being absorbed when finishing the cabs.

Mix enough ZPoxy so you can mix in in the sanding dust with the remaining Zpoxy in your cup and make a nice thick paste and smush it into the gaps to fill it. Place the flooded wax paper along the joint to create a mold for the corner edge joint. This is shown in the linked thread. 

Glenn