Model Five Restoration and Some Questions

[meta_noia_fot]

Hi everyone,

When I went to Boston and bought my AR-91's, I also added a pretty beaten up pair of Model Fives to my collection. I only paid $50 for them which I figure is about right for the shape they were in. These photos are of the worst sides of the cabinets. Not sure what the black on the bottom of one is (mold?). Someone also definitely put a potted plant on top of one.

Between them, both tweeters and woofers are working, but both of the midrange drivers in one cabinet were out. I've ordered and received replacements for those, both made in the same year as my working midrange drivers (1969). I've also ordered npe caps from Dayton Audio and 15w resistors from Madisound. While I wait for parts, I figured I'd share my progress and ask a couple questions.

I spent a day this week working on the cabinets. I started by painting the baffles flat black. I first saw this in the excellent video series by @thr33p4c. In addition to this board, those videos have been a terrific resource. I got uneven results: one cabinet had a little more sheen. I flattened out the sheen using a some #1 steel wool.

Based on a thread I found here, I stripped the old finish using Blue Bear Paint and Urethane Stripper. I had the same experience mentioned in the previous thread: the old finish came off as a sludge using a putty knife. It seemed to me that a significant amount of the previous finish came off using the stripper. I hand-sanded the edges of the cabinets then used an orbital sander for the majority of the work.

There are some corner bashes and small bits of missing veneer on each cabinet. I'm going to try Kwikwood mixed with Mixol 22, again another decision based off the Novalux videos. After that has set, I'm going to apply dark walnut Danish oil. I plan on doing three coats over as many days while I work on the crossovers. While all that is going on, I'll seal the woofers and midrange drivers with The Goop™. Neither of my grills are in good shape, so I'm planning on making new ones, something that would be new for me.

Here's some questions:

- Despite best efforts, I still went through veneer on a couple edges. My plan is to use a small amount of paint on these spots before the danish oil. Does anyone have a recommendation for a paint brand and color for this touch-up work?

- What's a recommended grill cloth for these? Is it possible to find a comparable material at a store like Jo-Ann's?

- What is proper positioning for these? I saw the ad in the library said floor or shelf. If placed on the floor, is it better to use stands?

Edited August 27, 2023 by meta_noia_fot
Added a third question

[genek]

White discoloration is moisture that has penetrated into the finish but not into the wood. Black discoloration is moisture that has penetrated through the finish into the wood fibers (iron in the water has chemically reacted with tannins in the wood). White comes off with finish removal. Black can only be removed by bleaching. You can't sand it off, because it's essentially dyed the wood fibers all the way through.

Your best bet for sandthrough is to apply a topcoat finish rather than a penetrating one. Oil finish over touchup will never look the same as the wood, and if you oil first the oil will make the exposed particle board darker and harder to conceal. Apply a light coat of sanding sealer, followed by a first coat of varnish or lacquer, then touch up the sandthrough with paint or color sticks, toner and graining pens, followed by a second coat of varnish or lacquer. 

You will never find one single colored cover that will be a match for your base color. Your best bet is to get a kit containing different shades and some toner, apply a lighter shade to cover and then several light applications of toner until you get a good match, then grain. 

You must apply sealer and a first coat before touchup. You cannot touch up raw wood and get a match when a finish is applied.

 

[meta_noia_fot]

@genekThanks so much for your thorough response. I’m going to ditch the Danish Oil and go your route. Hopefully I’ll have some results to post in the next couple of weeks. 

[meta_noia_fot]

Well it’s been a few months but I finished the Fives today (for now anyway). 
 

My attempted touch ups of the sanded through areas….didn’t go so great. After a few attempts I ended up with a result that almost highlights those areas. It is what it is (for now). In the future I may sand through the varnish and reattempt touch ups. Thankfully those areas are small. I’ve learned that this hobby (for me) is very recursive; I’ll go back and fix mistakes once my skills have improved.
 

As for the finish, I decided to use glossy spar varnish. It’s not true to what was on the veneers originally, but I think it makes the veneers pop. This was my first use of spar. 
 

I replaced all the caps and replaced the resistors with beefier 10w resistors as mentioned on this board. Resealed all the woofers and midrange drivers. 
 

The project concluded today when my wife and I made new grill frames and installed fabric. I haven’t wanted to play these speakers much because I’ve been afraid my toddler would push in dust caps without grills on. I used Guilford of Maine’s wheat colored acoustic fabric. It’s enough off white that it looks somewhat aged, but still very clean and bright.
 

I moved my AR9’s out of my main listening area to install these. They’re less than have the size of 9’s but they’re far from half the sound. I really love these after only a few hours of critical listening. I can understand why someone in the 60s or 70s would have chosen these over AR-3a’s between the great sound, lower cost, and higher impedance. Beautiful speakers. 

[genek]

Can you shoot some closeups of the touchups that didn't go well? Maybe we can provide some suggestions.

[meta_noia_fot]

Thanks for the offer and your prior advice, @genek. I know what I did wrong, I just need to practice more. I’ll post some pictures of that area when I’m ready to circle back around to working on these. For now I can hide the corner with the sand through against the wall and no one who comes in the room will be the wiser.

Frankly I’m just glad the grills and grill cloth came out so nicely. I think those being so neat helps hide some of my shortcomings. I’ve been avoiding working with grills because I had very limited experience working with cloth. But this weekend I did these, a pair of AR- 4x’s, and I redid my AR-6’s. I feel confident enough that I’m going to redo my Model Fourteens with the leftover cloth I had from this project. 
 

 

[meta_noia_fot]

I’m not sure I’ll garner a ton of sympathy with this post, but here goes…

I have a vibration problem with my Fives. It’s coming from the back of the speaker and I can only figure it must be the backplate. I’ve thoroughly tightened down everything on that plate, so I believe it’s the plate itself. I glued the backplate in using wood glue as in the Novalux video series on YouTube. 
 

This happens on very low, loud passages. Specifically the track 1st 44 by Aphex Twin. Within the first three seconds, the backplate will rattle on those sustained notes. I’ve mentioned this track before on this board and it’s one of my favorite bass testing tracks. I know that modern electronic music uses bass far outside what was contemplated by the designers in the 60’s, but it’s what I’m into and I like the nice, tight bass that these old acoustic suspension speakers put out. The music has to be on the louder side for this problem to appear, but I’m driving them well within the rated power handling limits, of course. 
 

Is there anything I can do to cease the vibration? If I pull the crossover and backplate out again, is there something—some material—I can add to the seal there that would make a difference?

[RoyC]

7 hours ago, meta_noia_fot said:

Is there anything I can do to cease the vibration? If I pull the crossover and backplate out again, is there something—some material—I can add to the seal there that would make a difference?

Both of them? Just wood glue? All of the KLH 5 boards I've seen were installed with screws and had foam gaskets under them...no glue at all.

Roy

[meta_noia_fot]

Hi @RoyC
 

He’s talking about the glue bead and plate loading at 9:20: 

 

And it’s both cabinets, although one seems to vibrate at a lower volume and than the other. There was no foam gasket for the backplate on mine; only the remnants of glue. 
 

George

edit to clarify: one backplate vibrates when the program material is softer (but still loud), but I have to push the volume up a bit to get both backplates to vibrate. 

[RoyC]

Imo, wood glue is a very poor choice for this application. E-6000, Goop, or Gorilla Clear Grip (or some other strong contact adhesive) would be a much better way to go.

[meta_noia_fot]

Thanks, Roy. I’m adding opening up the Fives to redo that glue to my project list.