My AR-91 Resto-Mod

[ar_pro]

I've had these AR-91 cabinets for several years, and they were in such bad condition - chipped & gouged veneer, dented corners, and Acoustic Blankets that looked like they'd been chewed by a wolverine - that I'd come close to tossing them a few times.

Over the past few months we've been working on converting the third floor of our house into a dedicated listening room that'd give us more space for our main speakers & system, and get them out of the way of curious guests & children. This move would also serve to eliminate the TV/audio conflict that happens from time to time.

We were going to look around for a pair of speakers to combine with the Mac integrated amplifier, turntable & media player that would remain in our family room, when it dawned on me to do something with those old AR-91 boxes. eBay and Craigslist supplied a pair of square-magnet woofers, a pair of AR-9 tweeters, and a set of AR-91 mids. I also picked up a second set of crossovers in case there were any issues with the ones in the '91 boxes.

The decision to change the look of the speakers was something that I'd been thinking about for a long time. Some might recall the several AR-9 rehabs that my son and I had done over the years, where we removed the felt blankets and vinyl faceplate stickers to reveal a clean, walnut-faced appearance.
In all honesty, some of the cosmetic choices that Acoustic Research made in the era of the AR-9 leave me cold. Love or hate the effect of the blanket, it was always stone ugly, and when combined with those dissolving foam inserts, the result was inelegant, at best. On the '91, there's a partial blanket, the same foam inserts, a useless plastic panel (with a vinyl sticker!), and a painted, unveneered front face to deal with.

Being unwilling to re-veneer that big box, I decided to bondo, prime & paint the whole thing. Having had experience removing the blanket from the AR-9, I didn't anticipate the work involved to rid these 91's of theirs. The usual method is to get a good grip on the blanket with a pair of pliers, and slowly separate the felt from the cabinet surface - this has worked very nicely in the past. That said, on these blankets, it seems as if AR had used some sort of surplus Cold War-era Warsaw Pact armor adhesive, originally designed to field-patch a Russian tank. It took several applications of chemical stripper, and hours of sanding to remove every trace of the blanket! Never again.

For the finish, I went with several coats of sanding primer, and three coats of automotive urethane paint in satin black and clear-coat that I had sprayed at a local body shop. The tweeter faceplates, midrange trim rings, and woofer cosmetic ring were painted flat black, giving a nice uniform appearance to the drivers, and all of the mounting hardware was cleaned & sprayed, as well.

The idea to do something different with the front panel evolved over time - I'd been doing some reading on textured finishes, and decided to experiment with Krylon stone spray paint. Over several test panels, it became clear that the differences in the color and material sprayed from each can of Krylon was so variable, that I'd have to use several cans to get the effect that I wanted on both speakers. In the end, there are five coats of Krylon on each front panel, sprayed from seven different cans; and there are four coats of clear acrylic sealer as a finish. Krylon calls the finish "obsidian", but I think I prefer "asphalt roofing shingle" - it's just the appearance that I was looking for.

I'd removed the stuffing over the crossover to swap out the original caps (all Parts Express Dayton replacements), test the switches (the ones on the AR-91 are much better than those on the AR-9), and double-check the binding post connectors. The orginal grill connectors were removed & replaced with new ones from PE.

One note for anyone working on AR speakers from this era: the cabinet stuffing is starting to change - puffy clouds of particles can be seen if the stuffing is disturbed or removed - handle with care, caution and a dust mask!

All of the drivers went in without a hitch, although I needed to re-set a few of the woofer T-nuts. The worker who was responsible for originally fitting these did a crap job - he might be the same guy who randomly stapled the crossover boards, with 50 on one side, and 3 on the other - I'd like to hit him with my Graig Nettles Louisville Slugger.

We had a pair of speaker stands constructed out of 5/4" steel tubing - they're sand-filled & spiked, and topped with a slab of Pennsylvania bluestone - that raise the tweeter to the same height as the one on an AR-9. The Mac amplifier provides 200 watts/channel, and we're using a NHT B-12D powered sub, crossed over at 40 Hz for extreme LF support - most of the time, you wouldn't know it was there, as the AR-91 bass is outstanding.

In a nutshell, I'm very pleased with the result - I can't imagine any current-production loudspeaker approaching the performance of this AR-91 at anywhere near what was spent on the rebuild.

[ADVENTAGIOUS]

Stunning!

[ra.ra]

Really great job on those speakers, and I'll agree with you that they look better than the original aesthetic approach. Good for you for finding a way to use the original cabinets, and for putting together a very fine and unique approach to this salvage project.

A+

[owlsplace]

Wow, I've used the sand finish before on other projects and liked it.

So, are you going with or without grills?

[ar_pro]

Thanks for the comments, guys - they're much appreciated.

I do have the grills, Roger, but I'm inclined to leave them off.

Here's a shot of one of the AR-91's with its grill in place, and a photo of a blanket-less AR-9 that used to be in the same location.

I kind of prefer them without the grill panels.

[Steve F]

I owned 91's for several years, having bought them new in 1980. I've always thought they were outstanding speakers, very little to criticize or complain about. I have 9's now--re-capped and re-foamed--and I love them, but AFAIC the 91 was 95% of the performance for roughly 50% of the price. And as strange as the cosmetic choices were that AR made for the 91 (completely agree with you) the 9 and 90 were simply bizarre, almost like their looks were a practical joke played by AR on anyone who bought them. "You want this sound? Well, you have to put up with these looks. Ha!"

Your 91's look truly great. I think all the choices you made were spot on. A set of speakers like that--looks, finish quality and acoustic performance--in today's market would easily be several thousand dollars for the pair.

And well worth it.

Steve F.

[RoyC]

I agree with all of the positive comments above, and love the idea of utilizing the local body shop for the finish work!

Really nice job, ar_pro.

Roy

[DavidR]

Wow! I really like the 91 'naked' look you created.

I've been enjoying mine on a 500wpc Emotiva and liking them a lot.

Enjoy.

(I enjoyed your humorous comments)

[JKent]

Beautiful job ar_pro. You've earned your name!

The body shop finish came out great but I have to admit I never went that route because I "assumed" it would be very costly.

On my AR-94Si's (and some other speakers) I used truck bed liner spray--one can per speaker for the 94s. It gives a pebble finish that looks nice, especially on small speakers, but it's not nearly as elegant as your mirror-smooth 91s. Great job!

-Kent

[rjr513]

Beautiful work and I agree ar_pro i would have to leave the grills off also

[owlsplace]

Naked looks good I must admit or a sheer see-through grill

I have some naked infinity's in my bedroom...

[VintageMan]

Stunning!

Absolutely!!!

They look like the Tannoy DMT monitors line

[owlsplace]

Thanks for an idea on how to refinishing my ADS L-980's although leaving the grill off would not be an option with those sticky domes however the gloss black lacquer and sand finish look great together and certainly would hide a multitude of sins....

[ar_pro]

Thanks, again fellas - this really was a circumstance where the condition of the boxes called for something other than a straight-up rebuild to original appearance.

Also, I do admit to not being a huge fan of AR's aesthetic approach in the Verticals series; form should follow function, and as Steve F. explained, it's almost as if AR dared you to put up with their appearance.

This is not anything that I would've attempted with a speaker from the Classic period; AR's design choices in the '50s & '60s set the tone for the entire bookshelf loudspeaker market, and 50 years later, they've acquired a sort of timeless quality.

The irony is that when AR had absolutely no interest in gussying-up their drivers for the sake of appearance, their loudspeakers were unimpeachable beauties, but when they put some thought & effort into what the speaker would look like with its grill removed, they really came up short.

Kent & Roy: the price of painting was really pretty reasonable.

I was referred to a local supplier of finishes to auto repair shops, and they formulated a custom mixture of the right shade & sheen of black, with the correct amount of curing agent.

One quart ran about $85, but I saved a lot of money by doing the bondo work, and priming & sanding the surfaces myself, so I was only into the body shop for about 2.5 hours' work.

Because of the variation from can-to-can, the Krylon paint wound up costing about $75, but some of that was due to having to test-spray a few plywood panels until I got the result I wanted.

Roger: I'm going to make grill-less the default setting for the 91's, but I'll put the grills back on for parties, and the like.

For some strange reason, people feel compelled to poke at domed tweeters; so out of sight, out of mind.

[DavidR]

.......................................................................................................................................................................................

.......................................

Roger: I'm going to make grill-less the default setting for the 91's, but I'll put the grills back on for parties, and the like.

For some strange reason, people feel compelled to poke at domed tweeters; so out of sight, out of mind.

Yup. My brother in-law has to touch all the drivers. I always have to be on guard when he's around. I just don't get it. Even if I tell him not to touch he'll say it won't hurt anything and I say "yes. it will". I then I tell him eBay is full of dented drivers that nobody buys.

[Pete B]

Did you strip the veneer before the sanding primer or just go right over it?

[owlsplace]

Yup. My brother in-law has to touch all the drivers. I always have to be on guard when he's around. I just don't get it. Even if I tell him not to touch he'll say it won't hurt anything and I say "yes. it will". I then I tell him eBay is full of dented drivers that nobody buys.

Maybe a static generator is in order with a proximity switch

[ar_pro]

Pete -

The veneered sides & top, as well as the painted front & back surfaces were all sanded with 100 grit paper to remove the original stain and paint.

Chips & dings & holes were then bondo-ed, and all of the surfaces were sanded down with 220 grit paper.

I then applied consecutive coats of primer, sanding between each coat with 400 grit paper until everything was uniformly smooth.

The painter seemed happy with the prep, and he went ahead & applied three color coats and a final clearcoat.

The front panels were finished last, after allowing three weeks for the paint to set up.

[DavidR]

Maybe a static generator is in order with a proximity switch

I was think something a bit nastier (but not lethal).

A slight static zap might not be enough to curb his desire to touch.

[ra.ra]

Re: painting stage 1, was the front baffle masked for the professional spray process, or did they simply spray the entire cabinet? Re: stage 2: masking on all sides; five coats of Krylon; four coats of sealer; three weeks cure time - - - is that correct?

[ar_pro]

ra.ra:

After prepping, the entire cabinet was sprayed, including the front baffle.

I gave the urethane paint three weeks to cure, and then blue tape masked & papered all of the surfaces, leaving the baffle exposed.

I needed to sand off the clearcoat on the baffle with 400 grit paper to prepare it for the Krylon; I then blew all of the dust off, and went over it with a tack cloth.

Masking was also done around the tweeter & midrange recesses, and I placed bolts into the woofer mounting holes to keep them paint-free.

Then it was five light coats of Krylon over the course of an afternoon until I got the desired effect on both speakers, and I let it set up for four more days before applying four coats of acrylic sealer over about a two hour period.

The Krylon & sealer surface were rock-hard within a day or so, and without any residual odor.

Just a note: I removed the masking tape as soon as I'd finished painting the baffle; when it came time for the sealer, I re-masked each cabinet, and removed the tape & paper as soon as I was finished spraying the sealer.

[ra.ra]

Many thanks for the details - - - excellent technique and description on your processes. And I agree, Krylon makes some very good simple-to-use paint products available to the general consumer. While we're picking your brain, anything specific to describe on the crossover assembly? Also, regarding the speaker stands and overall set-up, are the speaker cabinets set directly on the bluestone, and is the stone simply loose laid on the tube steel or did you use further isolation? Again, kudos to you - - this is a great project.

[ar_pro]

Nothing special regarding the crossovers - the single access point does make you appreciate the twin woofer holes on an AR-9, though.

As mentioned, the caps were all PE Dayton 5% types. I did buy an extra set of AR-91/92 crossovers from eBay, just in case there was a problem with either of the original boards, but they were fine.

The level-control switches are more robust than those on the AR-9, and there's absolutely no sign of an intermittent connection - they feel like new switches.

We had the stands built by A&M Fabrication http://www.aandmcustomsteelspeakerstands.com/#!

The idea was to place the tweeter at the same height as the one on an AR-9, so we factored in the thickness of the stone.

The 1 1/4" bluestone slab was cut to slightly within the perimeter of the stand, with a flame edge all around; the stone rests on four of those soft rubber stick-on feet, placed at the corners of the stand.

The steel stands are sand-filled, and spiked, so they sit very nicely on the carpet, and are easy to level.

The speakers have the same soft feet, which lift them perhaps 1/4" above the stone.

I'd originally considered removing the small plinth below the cabinet, and spiking the boxes, but decided it was overkill; and the cabinets actually look pretty good with that slight elevation, too.

I did secure the plinth with 4 additional screws, as it's only slightly attached with thin brads and some hot glue (no kidding, check out the blueprint).

So here's a heads-up when it comes to lifting an AR-91: don't count on that plinth staying attached!