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The pair of speaker crossovers shown here (with #5 coils, however) had the same situation regarding mis-matched capacitors, and even though the can-type caps often still measure reasonably well, it is a good idea to replace both 20 uF caps at the same time. You can always parallel multiple smaller caps to achieve this value, or simply replace with a single good quality cap of the same value. And if you want to ensure the best HF performance from the tweeters in your restored speakers, while you are inside, you should also inspect, and then decide whether to clean or replace the pot controls.

I recently re-foamed these same woofers which were Tonegen factory replacements for a pair of AR-7's, and I used the Bose 301 surrounds recommended by Roy C. The Boston foams may be a bit more compliant, but the Bose is a better fit and a very suitable surround. Easy install, but that weird dust cap is a delicate process to re-attach if you use shims. Has anyone else encountered this elastic ring along the inner surround crease? It felt like a thin bead of silicone, and it peeled off with ease. I suspect that its original purpose was to create a profile similar to the Boston filled fillet regarding sound wave diffraction.

Great info from m-pat and RHolt. For those of us who aren't skilled enough to fully understand the mutual inter-workings of driver sensitivities, crossover slopes, and the subsequent effects of caps and coils that go into the design of any speaker model, this is all interesting and helpful information to consider. It makes me want to possibly experiment with adjusting some cap values on some speaker projects where I have transplanted similar, but not entirely original, drivers due to availability.

Sounds very plausible, thanks, mi-pat.

Fantastic collection and great photos - - - the AR-18 (and 18s) does have a fervent following, and I always love to see the enthusiasm for AR's small two-ways. I'm wondering if that small dimensional change accounted for the minor bump in internal volume, and I'm also curious about the change in cap value from 6uF to 5uF. I, too, prefer the aligned drivers in the 18s, but it's too bad they abandoned the two-way tweeter switch from the earlier 18. Thanks for sharing.

Roger, there are more than a few members on this site who know the intricacies of these models better than me (michiganpat, Robert_S, maybe?), but yes, the AR-18, 18s, and 18b all used excellent drivers worth salvaging if all else is beyond repair. Not sure if any of the earliest of the 18's had real wood veneer cabinets, but even the 18 and 18s (see pic) had at least three differences: driver placement, tweeter (both had FF, but different lead-out wires), and woofers. Some '18' models use a 6uF cap; others have a 5uF cap, I think. I have some literature that lists the AR-7 and AR-18 as both having identical cabinet volume (9.77L), whereas it appears the AR-18s is listed as just a tad larger (9.86L). Close enough for government work, and they all have the same x-o frequency (2000 Hz) and use a 5 or 6uF cap, so my guess is that this 18s woofer might serve as a very reasonable substitute for an AR-7 woofer. The 18s woofer should be p/n 200037, same as in this 18b I recently re-foamed. I did not like working with this flimsy, shiny dust cap, but I just slit it, folded it back and shimmed, and delicately glued it back in place. Your question about driver polarity is a good one since the AR-18s has consistent polarity and the AR-7 has drivers reversed. I dunno - - - am still curious about the AR-7 wiring - - - why not try it both ways and report back.

LC simply refers to the two crossover components: inductor (L) and capacitor (C). A bit difficult to follow, but this thread shows a number of these LC devices and mentions the 630 model at several points. http://www.ebay.com/gds/EMI-350-style-combination-speakers-Single-Point-Source-Monitors-/10000000020917667/g.html

Hey Kent, this thread may become of interest to you. http://audiokarma.org/forums/index.php?threads/rare-emi-score.725969/

Yeah, those look really good, Kent, and many of us have encountered those cabinet problems that challenge our woodworking skills. Not long ago, I finished restoring a pair of AR-6's that were really beat up, and I had corner conditions similar to yours that required both gap filler and touch-up markers. I still haven't tried the "tootsie rolls" (Mohawk product?), but I've been having good results using this soft putty-like product - - - it's rather forgiving and the only downside is it dries really fast so you have to work quickly. http://eclecticproducts.com/products/famowood/famowood-original-wood-filler.html This long video shows a boatbuilder using this product, but his excellent tip (with the plastic bag) at the 4:00 minute mark was something I used to extend working time.

I love FM jazz, as well as the Hammond B-3, and the best car my mother ever drove was a lovely silver-blue Olds Cutlass, so I really like the peripheral elements of this story. But really it's the serendipitous synchronicity of pairing these components that is the main course of this meal, and it explains the reason we like to explore, de-construct, and tinker with these dust-collecting items. Really great vintage stuff.

No one wants to end this thread on a sour note. My participation was triggered by some simple discussion about the esoterica of little metal badges, but I will confess that I might tend to get a little overenthusiastic about the more modest offerings from AR's "classic" series - - - i.e., the small 8" two-ways. My previous comments were meant to be yet another cheerleading effort on behalf of the smaller speakers, but I was also challenging the OP's seemingly contradictory statement that he is seeking "something a bit higher up the ....food chain" (which to me often translates to 'larger') while stating the spatial limitations of his living environment. Spensar, stick around, this tent is big enough for a wide variety of tastes, practices, and opinions (you did miss a special bargain, though), but do keep us posted on the eventual acquisition of your 'keepers' once you procure them. And to larrybody, I shook hands with Bobby Kennedy before I ever knew of Acoustic Research and I'm good with that, but there is no snark in this thread - - - all comments have been supportive and cooperative to the OP's questions, and it has been a healthy exchange. You stick around, too - - your posts have been great. But, when the time comes that I feel the need to post a pic of Henry Kloss on my wall, there is no doubt that I will prominently display this visage of HK. Cantankerous genius perhaps? Maybe, but I'm good with that, too.

Thanks, Kent, for clearly stating my exact thought. Am just not clear about how someone who has limited space will be able to accommodate something "higher up the... food chain" (AR-3's?) without spending 20 times as much as this sale required. IMHO, E.F Schumacher said it best when he wrote in 1973, "Small Is Beautiful".

Hmmm, perhaps "incised" was a poor choice of word - - the recessed depth of the letter forms is probably created by an acid etching process or something similar. In any case, I just recently discovered what I think is the most effective and easiest means of cleaning up these badges, as shown on these AR-7's from two weeks ago. Using a metal polish and a piece of scrap cotton flannel, it's just a little squirt and a rub-a-dub-dub, rinse, and Voila! No other abrasives required. These badges were not heavily tarnished yet look at the verdi-gris left behind on the fabric swatch. Using this method, I'll probably re-do other "etched" badges, and then inhibit further tarnish with a light spritz of clear lacquer. Have not yet tried this with the black variety, nor have I found another suitable method for cleaning these.

Kent, you are correct about the TT badge, shown here in upper right of first pic still attached to wood plinth - - - it is same size and similar appearance to black 4x badge but with incised lettering - - a nice little detail. Also interesting to note that some badges are attached to steel backer plate/screw, and others are simply all brass.

Yes, welcome to the CSP forum, Spensar. I hope you come home with that quartet of 4x's tomorrow (or could they be 4's?). The AR-4 has a small square badge (15/16") with black "AR Inc." screen printing. This same badge was used on the early 4x's, but was later replaced with a small square badge (7/8") with an incised "AR" in red-brown lettering. This later incised style was subsequently used in the following models (and maybe others?) in various rectangular formats: 2x, 2ax, 2xa, 3a, 3a Improved, 4xa, 5, 6, 7, MST, LST and LST-2. I believe the much-maligned AR-8 never earned the incised badge, and I am not sure if this version ever showed up on any AR turntables. See below for two versions of small square badge.

I would be inclined to agree with Kent that both drivers are probably intended to deliver similar frequencies, but then again, it's a bit unclear what all is going on with that crossover board - - there are two resistors and one cap, and is that a coil, too? What this idea has brought to mind is a speaker model from several years later - - AR's MST-1 (3-tweeters, all identical) - - where the side mounted tweeter has a small additional cap in order to perform differently from the front-facing tweeters. The MST, of course, is a rather unique design regarding dispersion and an entirely different speaker, but is it possible that the 1uF cap in this KLH is associated with only one of the two small identical drivers? And here's a nice little ad from 1964 for the KLH Fourteen in both styles (S-slimline and B-bookshelf), including some high praise from Julian Hirsch.

Your work looks very neat and precise, so I do hope they play well.

Re: "thick", I suspected so, but just was not sure. On the cones, I'm only trying to offer a word of caution since I know how tenaciously some substances adhere to those heavily textured paper cones. It appears you may already have an excellent surface to attach the inner foam, so I would hate to see you make it worse.

That black ring on the cone perimeter looks so smooth (except for that one location) that I'd be tempted to attach the new surround directly to that existing rim. With regards to trying to remove that ring, my concern would be the possibility of doing more damage to the cone than making any improvement. Why remove it - - are you concerned about added cone weight? My thought would be to leave cone as-is and simply clean up the metal basket frame to ensure a neat glue joint. In your first post, you mentioned that the rubber surrounds were "very think", and it is unclear if you meant "thin" or "thick".

One additional thought to consider. Unlike the AR-3, which was still considered a bookshelf speaker (albeit a large one), both the High and Low versions of the Rectilinear III were intended to be floor speakers, as suggested by their integral wood bases. Compared to the AR-3 which offers a vertical or horizontal placement orientation, the Lowboy, with the wide and squarish proportions, has a very different presence as a piece of 'furniture' in a room. I have seen pics of the Lowboys raised up on additional stands to elevate the drivers, but the speakers look sort of ridiculous when lifted this way. For interest, a pic of two versions of Rect III "Highboys" is attached.

You cannot only compare the cabinet depth - - - all three dimensions that make up internal cabinet volume need to be considered. For example, the AR-17 and AR-18 are nearly identical speaker models - - same drivers, same HF control, same x-o - - but the AR-17 has a slightly larger cabinet volume and subsequently deeper LF bottom end (43Hz) than the AR-18 (48 Hz). Why AR felt the need to manufacture the AR-17 is beyond me, but how else can this slight LF performance boost be explained?

Have never done a side-by-side of these two models, but I am a big fan of early Rectilinear models. I'm sure you already know that the Lowboy was a re-packaged (different cabinet proportions, fretwork grille) version of the highly regarded Rectilinear III, which subsequently came to be known as the "Highboy". These models were probably targeted toward some of the market share that was dominated by the AR-3a, but they are distinctly different speakers. They have six drivers (12" woof, 5" whizzer mid, plus two small tweets and super-tweets), are ported (bass reflex), and have nominal rated impedance of 8 ohms. I'd suggest you go and give them a good listen, then decide. Julian Hirsch gave them a big thumbs-up in this 1972 review. http://sportsbil.com/stereo/rectilinear-db/lowboy-review-hirsch-2-1972.pdf

lakecat's comment about the bass response from the AR-12 made me curious, and I was surprised to learn that, unlike the earlier "Classic" series where the 10" AR-2ax and AR-5 had less cabinet volume than the 12" AR-3a....... in the ADD series, the 10" AR-12 (and AR-14) has the same cabinet volume as the 12" AR-11 and AR 10pi models. Two possible benefits? Maximize manufacturing cost economies of scale, and get an extended LF bump for the 10" woofer.

Hey Glenn, as with all of your salvage-restorations, those AR-12's look terrific, and I did follow your progress over on AK. This speaker just does not show up all that often, so I am pleased to see a pair so carefully restored, and I am sure they sound great. What makes this model unique is that odd mid-range driver, which I believe may not have found its way into other AR models. Great work, thx for the post.

Thanks, Tom, for distributing the sad news and providing the photo. This attached pic from 2014, cribbed from another website, has always delighted me. This woman had just purchased a pair of speakers directly from Roy in NH, and their mutual joy with this particular transaction appears evident.