AR-90 refinishing update

[Guest radkrisdoc]

Just as an update, my AR speaker refinishing has reached the final prep stage. I have finished sanding all sides, and have also taken quite some time to work with the smaller scratches, dented bottom corners, etc. I used Minwax High Performance wood filler, a two part (?epoxy) filler. I found this to cure to a very hard form, unlike the other Minwax product called Stainable wood filler. Minwax claims both are stainable, but of course they won’t match the surrounding wood. I've used filler only under paintable surfaces so I won’t have any trouble matching stain. The bottom corners were pretty good for a 20 yr old piece, but well, I like edges and corners that are prim and proper. I have a bit more filling/sanding to do and the speaker will be ready for the finish.

I also had an idea earlier to convert the 8” LMR’s enclosure to aluminium. I actually did work on the aluminium part, but when it came to dismantling the original enclosure, I hesitated because it was pretty good anyway. I’ve decided to keep the aluminium tubes for an extra pair of AR drivers, only the tweeter/mid/lo-mid combo, maybe for use as surrounds. They will only need a MDF baffle to keep them all together.

I had one dark ring on a speaker, apart from various small scratches/indentations on the veneer probably caused by the speaker’s own weight during transportation. I sanded out the ring and fine scratches. As for the indentations, they looked like imprints of speaker wire stuck between the speaker and a hard surface, probably caused during transportation over the years. They were more than 10 cm long on one side, with other sides having a few here and there. The veneer was not chipped or cracked; I could see that it was just indented. The internet proved to be a good source of info for this problem and I read a few articles on how to use water to swell raw wood where it was indented. So, equipped with only a fine screw driver, a glass of water and a hair dryer, I carefully applied water only to the indented areas, let the wood absorb water and used the drier to evaporate the water. After a bit of fine sanding, the veneer is now perfect.

Apart from this, I also had a different problem. It looked like some wise guy tried to restore the speaker and after using a stain on one side, probably abandoned the project. Result is, one side looks a bit darker and a shade redder than the other sides. For this problem, I used hydrogen peroxide (Sun Oxygen cleaner, available at Walmart, has only sodium percarbonate, no added detergents). The difference has been quite dramatic, it looks like new raw walnut now! I’ve included the “before” pic, will post the after pic later. This process did raise the grain a bit, which I plan to deal with fine sanding during application of the final finish.

The final finish…..I’ve decided to use Penofin. I just spoke to their customer support people; it’s advertised as an oil finish based primarily on brazilian rosewood oil. The customer support person also said that it has various other oils including linseed and tung. I will be buying different shades, golden oak, medium walnut and dark walnut and will try to match the earlier color.

Coming to the actual color problem, I want to ask those of you who were fortunate to buy AR speakers with the walnut finish new from the factory: How did the finish look like then? Did it look darker? Have you seen any walnut finishes getting lighter (bleached by UV) over the years? My AR-90’s have a light yellow finish, I would not call it dark; the pics below will give you an idea. I’d like to restore the speakers so they look like they did fresh off the factory 20 years ago.

The Penofin finish has two advantages: its an oil based finish, meaning, regardless of where the oil comes from, its chemistry will be the same making it compatible to linseed oil applications, if some future owner say in 5 or 10 years tries to apply linseed oil over Penofin; the other advantage is that the pigments in Penofin have the claim to reflect UV rays, offering protection.

Apart from all of this, I’ve sent the crossover components to my brother, who is an engineer and a graduate student with access to a University lab. Even though it will take him a long time to get to it, the measurements will be of good standard; if there are discrepancies in coil values (maybe they have been tweaked, I don’t want to take anything for granted, I’ll know if the left and right speaker components don’t match anyway) he will be able to fix the discrepancies as well.

That’s it for now. The project has been very interesting and fun to work on. I’d also appreciate any kind of input from you all in the forum, especially with the color question. Kris

[Guest radkrisdoc]

Hi everyone!

I've been a silent observer all these days, had a lot of things going on in my life. This post has been long pending in my to-do list. I am done with the re-finishing part of the AR-90 project I started a year ago, here are the pics....

The cabinets were stripped, worked on with putty to repair disfigurations and first oiled with Penofin (wet sanded upto 2000 grit), masked, painted with primer and the black finish coat. After I gave a month for everything to cure, I applied two coats of wax for the final finish.

I have not yet assembled the crossover or mounted the drivers. The speaker cabinets are in storage right now at my brother's place. I will be working on them as I get the time. I also had the inductors measured using professional lab equipment, because I had noticed the plastic spools from the two speakers were of different colors. Thankfully though, all the coils have exact values, matching up with the schematics available in this site. I am planning on replacing the capacitors with Solens and Nichicon electrolytics; I've bought the Solens already.

I've enjoyed working on this project very much. And the speakers look awesome now. Kris

[rrcrain]

Most oiled wood finishes become darker over time, Black Cherry being the best example I can think of. By comparison, walnut remains relatively color stable as long as its in a temperature controlled environment and not exposed to the sun. I know for fact it will bleach out if one side of an AR90 cabinet is exposed to the sun, even thru a curtain. I had a horrible time maintaining one cabinet while I lived in Colorado. One side of one cabinet needed attention twice as often as the rest of the cabinet not exposed to the sun.

Color wise, the original walnut is not a dark walnut but definitely not light. Closer to a brown rather than red as some of the new walnut finishes from Salamander Designs tend to be.

[Guest radkrisdoc]

Yes, the original walnut veneer that the AR-90's come with is definitely not "American" walnut. I got a few samples of "American" walnut thinking I'd use them to see how different stains worked, because I wanted to get as close to the original linseed oil finish; the pieces I obtained were very different from the veneer on the speakers. Much darker, slightly redder too. "European" walnut is much lighter and similar to the veneer on these speakers.

The pics I have posted here have different shades due to varying light intensities. I am no professional photographer, wish I knew that too, I've got future plans to develop that as a hobby.

All in all though, the speakers are wonderful to look at, very close to the original linseed oil finish, just a tad bit redder, that gives the finish more warmth, but the flexibility remains: if I were to reapply boiled linseed oil after a year or two, the finish will be compatible, no stripping needed.

UV from sunlight bleaches linseed oil finished walnut. That is why I chose Penofin, because of all the hype about the pigments in it that are protective against UV light. Now all we have to do is wait and see how good it stands the test of time and sunlight.

[Tesla43]

they look beautiful did you ever finish?