meta_noia_fot

Thanks. The lacquer on these cabinets is certainly going to complicate each step of this.

Sanded down today. This is walnut, right? I’m second-guessing myself.

Thanks @JKent. I never would have thought about steaming dents. I’ll keep that in mind. I’m worried this has the same lacquer finish as the Five. Looking at the most damaged top again today, I can scratch off some of the most damaged finish with my fingernail. I’m also concerned some of the black spots will need to be bleached out of the wood.

Here’s a couple specific questions about the cabinets: 1. Would clamping the corner split in any way improve it or is it too far gone since the boards have swollen from moisture? Is there anything else that could be done? 2. Is there anything that can be done about the finish on the top and on scratches? Does the Twelve use the same, hard to remove finish that the Five does? Normally I might try Howard’s Restor-a-finish as a first attempt but not sure if that will work on these. The parts that are rough, are pretty rough. They’re not complete eyesores, but they’re not beautiful either. I think these are very nice sounding speakers and deserving of better looking cabinets, just not sure of the feasibility of some of what needs to be done. This is something I’d tackle longer term—probably late summer. My confidence with crossover work is much higher than with cabinets. Any help would be greatly appreciated.

I’m looking for some cabinet advice. Since these have external crossovers, I wanted to listen to these awhile before deciding to undertake any cabinet work. Now I’d like to know, what could be done about the cabinets? Pictures are of the worst of the two; the other doesn’t have water damage. The corner splits are cosmetic only and the interior of the cabinet is still sealed. Lots of miscellaneous scratches like the one pictured on the front.

Here’s a few more photos of the cabinets before I remove the drivers. I’ll try that. Likely it will be effective since the varnish is just rubbing off on my hands while moving the cabinets around.

I picked up a set of AR-2’s recently and figured I’d document my progress here. All original parts and no one has been in them before. Today I removed the grill cloth and the cardboard grill that was glued and stapled to the baffle. I plan on making removable grills with Masonite leftover from my Model Five project. The most noticeable flaw with the pair is that someone with even less cabinet knowledge than even me attempted to varnish over the original oil finish I think. The varnish is flaking off everywhere and the cabinets have a sickly greenish hue. I’m hoping to get these sanded down this week. Tomorrow I’ll take out the drivers and look at the crossover. Hoping to see oil capacitors.

Finished these up tonight. The silver cap was actually an Industrial Condenser Corp. cap. Those two 100 mfd caps measured 148 and 126, so I replaced them.

I would be interested in this. I have a pair of 4x with the tweeters from Vintage AR. I was showing my wife this and we think we could get an adapter done. This is beyond my abilities alone but she’s a trained theater tech and has helped me with projects on here in the past. I also have a turntable part I’d like to get 3D scanned so I could kill two birds there. For evaluation, what do you seasoned vets use to compare the tweeters and get quantifiable results?

Well I’ve spent my listening time today split between the Model Five, Model Twelve, and AR-3a. It’s not necessarily an even playing field; the -3a’s mids and tweeters have not been rebuilt, while I don’t believe the KLH drivers need any more restoration. But a couple of observations: In terms of pure, low frequency response, I think the -3a has the edge. A/B’ing between the -3a and Twelve using modern electronic music and some organ music, the -3a handles very low tones better. But it’s close. Between the Five and the Twelve (all tone controls flat), the Five sounds more forward on the mids and highs. I like both the KLH models over the -3a for rock music. Another fun experience was playing the Fives and Twelves together. That’s an impressive rock setup. Here’s a pic of the stack at the moment. All three of these projects wouldn’t have been possible without this forum, so thanks as always for that. George

Thanks @DavidR. It’s nice to have external crossover boxes (or easily-removable crossover boards like the Model Five). Much easier to make work look neat when you’re not working inside a cabinet. I thought the Five and Twelve crossovers were both fun projects.

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

I finished replacing all the caps and resistors. I’m going to go back and hide solder connections with electrical tape, but they’re finished enough that I’m able to test them. I haven’t done work this extensive on many crossovers; feedback appreciated. Lovely sound, as expected. Tomorrow I’ll a/b them against the Fives.

Adding: for an extra $100, these can be delivered to the Boston area

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.

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?

I had to replace one of the crossover boxes with one from eBay. When I opened the original up, there was a healthy mold specimen in the wood. I received the replacement crossover in the mail and it looks closer the original one that Kent posted. Thought it would be interesting to show them side by side, bearing in mind that the 50mfd caps in the crossover on the right were already replaced as mentioned above.

Thanks @RoyC. I had read previously that less sealant was needed on the mid surrounds. Those received a very light application. I also tried to be judicious with my use on the woofer surrounds, some areas still were not tacky or shiny after the second coat (primarily edges where the surround meets the cone and basket). I replaced the white foam gasket material with a ring of duct seal. I figured it may be better being able to press it into those screw channels. The above photos were before I installed the rest of the duct seal and screwed things down. I do think the seal is better now than with the old compressed white gasket. Thanks for your help George

Selling my spare set of AR-9s. Asking $800. Bought these intending to fix them and give them to family, but honestly, I don’t have a way to transfer them to the Southern US. Space is at a premium in my workshop so I’ve decided to part with them. All original drivers I believe, but I haven’t pulled drivers to confirm part numbers. One LMR woofer dust cap is pushed in. Probably needs to be recapped but I only removed one woofer to peek inside. All surrounds were replaced before me, although the subwoofers were a larger foam that someone cut down to fit. As such, there’s a radial splice in the foam. Also, someone drilled a small hole (maybe 1:4” in each backplate, I assume in order to modify the crossovers, but it appears they stopped. I was going to patch with some wood filler. Pickup in Midcoast Maine.

You and Roy are a wealth of knowledge on these. Thanks. I originally started this thread for questions about the crossovers, but I guess I’ll add some questions and observations about the cabinets. While I wait for caps and resistors, I’ve been working on resealing the cloth surrounds and sealing the drivers into the cabinets. Currently I have OK seals on the woofers. That’s after one layer of Roy’s sealant on the woofer dust cap and 2.5 layers on the surrounds (2 full coats and a touch up of spots that looked thin). When pushing in and releasing the woofer, I get a second or so before the woofer is back in its original position. Judging it against the seal on my Fives, it’s not quite as good…the woofer maybe returns in half the time as on the Fives. Is there anything about the large volume cabinet on the Twelves that complicates this process or should I be getting a similar seal here? It’s possible I still have some leaks I haven’t found. As for the midrange drivers, what’s the best way to tell they are sealed? On the Fives I just push one cone in and see if the other pushes out since they share the same enclosure. But since these have separate enclosures on the Twelve, is there a way to tell how sealed these are? I resealed each surround and plugged up the drilled wire holes inside each cabinet. A push-and-return test is pretty inconclusive to me on the midranges. Maybe they’re fine as is and I’m overthinking it. Speaking of the midrange enclosures, those are held on with four screws on the front of the baffle, unfortunately right where each midrange needs to seal. So more than not, each of those screw holes ended up with a small channel into the enclosure. I used duct sealer to plug those holes and to reseal the drivers. It’s unsightly but at least the grills and original grill cloth are intact so no one will have to see it. George

Thanks Kent. I already have replacement resistors coming in with the caps. I followed that same advice on my Fives as well. I ordered 15w resistors just because it was convenient for values from the supplier I used.

@JKent Thanks for your help! Those diagrams are terrific. And yes, that is the only double cap on mine. Speaking of, here’s a couple photos. Oddly enough, mine had two 47mfd caps instead of the two 50mfd. Pic of those too. They didn’t strike me as original but they were fastened down with the original cable tie. Maybe someone replaced the 50s and shoved the 47s under the same tie. I ordered 50mfd as replacements based off your previous work on the Twelve. Hopefully when I’m done my crossovers will look half as clean as yours.

I bought a pair of Model Twelves that need a restoration. I’ve ordered replacement caps and resistors but I have a question about the double 4mfd since there’s no available schematic. If I twist a pair of new 4mfd caps together so that they share a common lead, would that be the black wire in this photo of the crossover? That would leave the far ends of the double cap to take the place of the red wires. Thanks in advance

Thanks. I had no idea. I guess between the silver cap and redoing the seal in gasket tape, I’ll be opening these up again soon.