ra.ra
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Just a brief amendment here. The AR-18s cabinet drawing found in the Library includes some very detailed notes about materials and construction, and also confirms a number of production revisions which might account for the small differences discussed here. Also, it appears that the rear terminals that I have assembled are a facsimile of the those found on the Euro 18s, which is exactly the same as found in the variant AR-18LS, also a Euro model.
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2 hours ago, ligs said:
The AR18s was consistently rated as a "best buy" by the UK Hi-Fi press and formed the basis of many a classic system.
Thanks for the interesting information, ligs. This statement reminds me that I've heard our Euro friends mention that this model is something of a cult classic in the UK.
2 hours ago, ligs said:Some people believe a simple crossover leads to better sound, provided that woofer and tweeter are carefully matched.
This statement is crucial to the success of a few of the lower end models (18 and 28, maybe) of the 'S' and 'B' series that have these ultra-simple crossovers when you examine the slight changes in driver part numbers as cabinet volume increases. This statement also reminds me of the way the crossover became far more simplified in the final iteration of the wonderful AR-6 model.
"Ken Kantor .... also mentioned that AR sold a lot of AR 18 to studios." High praise indeed from both seller (Kantor) and buyer (studios).
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Hey Larry, I knew it was just a matter of time before you chimed in, and I was thinking about your impressive collection when I began this project. In fact, I dug up the thread where you described a recap and adding the binding posts, and I was considering ordering similar posts for these 18's before I decided to go 'old school' with the simple screw-nut terminals for reasons stated. Now you've got me curious to learn about your L-pad project. At one point, I did consider: should I add a two or three position attenuation switch?
From the pic of your eight 18's, there's a few details I'd like to confirm. Upper left appears to have a different badge? Both in column 2 seem to include a one-piece plastic trim ring on the woofer? Despite your added binding posts, column 3 shows one each of the different terminal backsides: upper has square cut-out with masonite panel and terminal strip (like mine); while lower has circular cut-out with square plastic cup with cap attached to cup backside (see below).
Larry's cabinets in column 3 point out something else I am now curious about: cabinet panel thickness. For the 18s pair shown in my project, the wood cabinet dimensions are: 9-5/8"w x 16-1/2"h x 6-1/4"d (published dims for depth will be greater since the grille projects beyond the cabinet). These cabinets utilize 1/2" thick side panels, which is the same as my AR-7's. By comparison, it appears that all of my AR-4 variations and multiple AR-6 cabinets use 5/8" thick side panels. My stable also includes pairs of AR-18B and 28B models, and these cabinets use 3/4" thick panel stock of lesser quality material. It appears to me that Larry's column 3 cabinets might be thicker than 1/2", perhaps contributing to the different sizes as he has noted.
Pic attached shows AR-18B crossover (28B is identical) showing circular cut-out and lesser quality particle board.
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All of the excellent ideas and supportive comments are most appreciated. Because the speaker performance remains essentially original, I did not really consider this a "mod" project even though one primary intent has been to achieve a renewed visual aesthetic. I suspected that even this level of revision might not be everyone's cup of tea, but at least no one has yet become aghast and accused me of blasphemy or sacrilege.genekGreat minds think alike - - - I have been trying to find the right project to employ a homebrew version of the "soft black" finish, which of course looks fantastic with the light linen cloth. I thought about it here, and could always do so in the future, but in this case wanted to first try the blonde look. Also, these cabs utilize the really tight, fine-grained MDF which, depending on personal taste, lends itself to transparent finish applications. Re: black, see pic attached of AR-18s - - not my speakers, but they do look great.MI-patIt was your endless praise of these 1-1/4" tweeters that originally peaked my curiosity and stimulated my ongoing interest in the AR-6, 7, 4xa, the 18's, and many other subsequent models; and I clearly remember your 58s project with the light grille cloth and thought they looked simply great. And yes, I gave the idea of new wood veneer some consideration, too, but was trying to exercise discipline to keep this a "minimal" project. And about "pulling the vinyl": while I do not wish to advocate that everyone go immediately strip their original speaker cladding, I do have to say that yanking this nasty stuff off was possibly the single most satisfying step in many speaker restoration projects I've experienced. It feels really good and is instantly gratifying. Grip it and rip it, yahoo!JKentThanks much for the kind words and added encouragement. I have absolutely no none nil zip nada zilcho idea of what's available on the market these days in new speaker options, but these little AR-18s are indeed fantastic small bookshelf speakers and can still be found for very, very, reasonable sale prices.My introduction to shellac was during 7th grade shop class (the girls took Home Economics back then) while in public school in Indiana, and then I forgot about it for about 40 or 50 years, but you never forget the unique smell (I mostly like it!). A pal of mine who is a harpsichord maker uses it in his gorgeous work, but he mixes his own from dry flakes and solvent (denatured alcohol), while I simply use off-the-shelf Zinsser Bulls Eye Shellac. It is available in clear and amber flavors, and I'd suggest to always thin liberally with more solvent. My mix here was about 1 part shellac to 4 parts alcohol and it was none too thin. Like everything, it requires some practice, but I'm just a weekend woodbutcher and even I can make it work. It tends to set up quickly, but if you make a mistake it can usually be rubbed out while still tacky or better yet after drying. It is an ancient substance, and it is derived from some type of tropical insect secretion. See Wiki page on this.ar_proHmmm... I had completely neglected to think to research Robert's Sound, but now I am curious about it. Am still unsure about grille choice, but like yourself, I rather like the black 'void' sans lower panel and may very well incorporate that as part of final solution.
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And a few random views....
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And the re-assembly......
About the crossovers: all original wire, but I just added some ring terminals and a little junction post, and filled cabinet slot holes with silicone. The caps measured slightly closer to 6uF than to 5uF, so I replaced them with dual 2.5uF mylar caps that I had on hand.About the terminals: the "classics" have terminals spaced 1-1/4" apart, but I opted for 1-3/4" spacing in order to use the holes left behind from the earlier terminal's rivets. Otherwise, these are pretty much like the early AR's, with lock washer and hex nut, etc. These are #8-32 screws, but instead of 3/4" length, these are 1" long to adequately extend beyond the 1/4" painted mahogany slat used on backside, which is sealed and secured with silicone. On the inside I added a rubber washer to ensure a tight seal but also as a slight shim, and the only knurled nuts available locally were brass. When fastened tight, these nuts sit at just the right elevation, allowing the cabinets to sit completely flat when laying on their backs.About the cabinets: the MDF cabinet panels had some small dings and very minor swelling, all of which was mostly made better with a simple hand block sander. Desiring a very minimal finish, I applied two very thinned coats of alcohol-based shellac and buffed it out to a near matte finish. On the backside, the original sales or service stickers were just too interesting to remove, and the AR-18s labels were attached using a hobby glue stick for adhesive. Rub-on numbers were used to identify the new terminals.About the grilles: still undecided what to do for long-term. The missing filler panel doesn't really bother me, but having another badge might eventually be nice. I have never liked the original deadly brown stretchy grille cloth. The grille frames fit great, but they place the grille fabric about 3/8" in front of the front cabinet edges instead of near flush like the classics. For short-term test run, I'm trying out some AR-7 grilles and as always, I think the off-white linen looks best.Am now done with this project for the time being, and these speakers are indeed little giant killers - - no wonder they were so popular as recording studio monitors. Sometime soon I hope to do a little side-by-side comparison with AR-7's and AR-18B's.
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With all of the recent threads about 4 and 5-figure sales prices for speakers, mega-watt amplification, and misplaced fervor regarding highly collectible models, this simple project from the other side of the tracks is bound to lull some of you to sleep with its low-rent appeal. On another audio forum, I was recently engaged in conversation with a member who has several pairs of quasi-rare 8" two-way AR's (AR-15, AR-17 and AR-25), and that dialog sort of prompted this thread to share an experience with a more common model. Much like the urge to rescue the irresistible sad-eyed puppy from the local animal shelter, these speakers were begging for a good home, so they jumped into two shopping tote bags and came home with me on the subway.Consider this another from the series: In Praise of Small Speakers. This is a pair of the AR-18s - - circa 1981, week 16 - - which came to me in reasonably good condition and with ample potential. Drivers were all very good - - no punched-in tweeter dust caps, and the woofers even had new foams and (non-original?) outer gaskets, which were a bit rough. The grille frames are perfect with all friction pegs intact, and the grille fabric is in G to VG condition. One cabinet is missing the small bottom filler panel and badge (anyone have a spare badge?). The 8" woofer p/n is 200037 (5.0 and 5.2 ohms DCR), the 1-1/4" tweeter is p/n 200038 (5.1 and 5.3 ohms DCR), and the entire crossover is just a simple 5uF cap in line with the tweeter. One minor point of interest was to note that the woofers are secured with machine screws and T-nuts while the tweeters use 1" wood screws.Took 'em home, wired 'em up, all is functional, sound is very good....now what to do? After a week of consideration, I decided to disassemble everything and make revisions to the areas I found unsuitable: the cabinet finish and the wire terminals. These original spring terminals are cheap things but they actually work pretty well with bare wire or pin terminals. But because I tend to use small ring terminals on speaker wire, my decision was to forego the idea of new 5-way binding posts and instead re-create simple screw terminals like the original "Classics".Just gotta admit it - - I really dislike the vinyl faux wood cladding on certain AR models, and this covering was already beginning to peel or bubble up in several areas and it just felt kinda nasty. Interesting to observe that this vinyl was put on as a single piece - - there is only one seam per cabinet, and you can locate it by closely inspecting the wood "grain" where it mismatches as it bends around the corners. Nonetheless, the vinyl had to go, and it simply peeled off "faster than a prom dress" (thx to John for my all-time favorite CSP quote). I also decided to remove and relocate the unnecessary and unsightly original model label from the front baffle board since it visually disrupted the otherwise simple and symmetrical layout. My intent was to create my own (budget based) silk purse from this sow's ear.
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1 hour ago, harry398 said:
I dont believe anyone could really articulate what you are looking to find
You're probably right, harry398, and I'm just trying to find someone to address this notion from a qualitative experiential perspective rather than solely from a quantitative set of laboratory data points. I very much like to obsess over comparative numbers as much as the next geeky dweeb, but as one sage advisor often noted, "It's all about the music." So my question boils down to: Unless someone can identify audible differences, why is anyone fussing with this in the first place?
Until I am convinced that there might be noticeable audio improvements as a result of various tweeks or substitutions (new caps, new foams, functioning controls, etc.), my own re-build projects tend to focus on two other areas that are important to me: 1) improved visual aesthetics (cabs, grilles, etc.); and 2) improved build qualities (wiring, connectors, terminals, straps, etc.). For both of these areas, the term "improved" relates only to my own personal preferences, and is not meant to suggest an improvement for anyone else's speakers.
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On September 4, 2017 at 0:56 PM, ra.ra said:
....how does cross-talk present itself in a measurable ... manner...?
Thanks for the referenced study, Carl. I guess I did ask about measurements, but since I was hoping not to be dragged down that rabbit hole, I will ask my question seeking a more subjective response. Can anyone describe the perceptible audible performance differences that result from these "improved" coil orientations versus the original co-planar layouts? And, if there is a noticeable superior performance resulting from the revised placements, can it be assumed that multi-coil AR speakers that have not undergone this "correction" are not living up to their full potential?
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1 hour ago, Carlspeak said:
You've got a high likely hood of inductor cross-talk in a couple of spots due to their same orientation and close proximity to each other.
I keep seeing this discussed in various conversations and I have no reason to doubt it .......... but exactly how does cross-talk present itself in a measurable or perceivable manner; in what ways does re-orientation provide improved performance; and why was this concept not enforced by AR engineers when the crossovers for these loudspeakers were originally laid out for fabrication?
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10 hours ago, DavidDru said:
Anybody have an impression/take on these caps?
Good question, but this response might not help you much. I am currently working on a pair of AR-18s speakers dated 1981 (36 years old) with the same gray 50V Unicon caps and the same 038 tweeter. Upon initial testing, these speakers sounded very good, but I have not removed and measured the 5 uF capacitor yet. On hand, I have some new caps that are itching to go to work inside these speakers as replacements, but because I have fairly recently re-built some AR-6's and AR-7's (probably even ten years older than the 18's) where the original blue NPE Sprague caps measured so good that I left them intact, I have not yet determined how to proceed on this AR-18s pair. Well, maybe I've just answered my own question - - I need to take the cap out of circuit and measure it before deciding what to do.
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Oops, here is the AR-93 and 94 comparison I had meant to attach.
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FYI, I had previously kept these drawings in a file, and they might have some useful information for you. One image confirms that, as you correctly suspected, the woofer foams were meant to be installed above the cones. A second image compares the parts of the AR-93 and AR-94, including driver p/n's and stuffing quantities, and cabinet drawings show that the 93 mid is installed in its own separate compartment, but not so in the 94. The third image shows the 93 crossover.
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The drivers in these speakers are very good, and as Tom noted, the AR-93 and 94 seem to combine existing parts into a new format for increased performance in a modest "package" at an attractive price point. With all of the AR's you've acquired, David, it's surprising you've never encountered this tweeter - - the 1-1/4" tweeter had various iterations: with and without fluid; straight or S-shaped tinsel leads; small and large magnets. This tweeter is a favorite of mine, and it paired well with many 8" two-way AR models, such as AR-7, AR-6, AR-4xa, AR-17, various AR-18's .... etc.
Shame about the re-foam placement, but despite that error, the work appears to have been well done. Up to you, of course, but I'd probably leave as-is and listen for awhile before even thinking about re-doing the foams. Not sure about the replacement felt around tweeter, but you might find something here - - when you locate the lower % wool material (45% and 75%, color: gray), the price is not so bad for some strips or a small sheet.
https://www.mcmaster.com/#felt/=193ha0e
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18 hours ago, stupidhead said:
oops
Yeah, no kidding, I guess it's me that deserves your online moniker.
Anyway, this is just a heads-up to everyone to know when to stop futzing. I had these AR-6 grilles looking good already, then went too far and ruined them.
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I think larry's progress on the right hand grille is coming along well. Aside from trying to prevent any warping of the grille frame, the biggest challenge with this process of trying to reclaim aged grille cloths is finding a balance between gradual lightening, in sequential steps, and assuring that the original fabric maintains its strength and structure.
As previously stated, I was using a diluted bleach solution, and that possibly contributes to weakening the aged fibers, but on many grilles I have been able to achieve excellent results with careful applications and monitoring. In the one case where I obviously was not so careful by wetting the grilles one too many times, the tensile forces which occurred during drying resulted in the disaster shown here.
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Hey, those are looking real good and thanks for the great pics. And I agree with you that a few battle scars give these things even more aesthetic character. With s/n's as low as yours, it's interesting to see that like the pair I showed, your woofers have neither the cross-hatch or the floral damping pattern painted on the cones, whereas larry-b's have both patterns (he probably paid more for that option
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Once you peek inside, here is what you should expect to see. And the most important thing: the dated personal stamp from the assembler.
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Just my $0.02, but here is the thread describing the successes (and one failure) I've had when refreshing aged AR grille cloths. lakecats' method sounds like it has produced satisfactory results as well, but I would not be comfortable with the idea of fully submersing the Masonite grille frames. Having said that, all of my AR-4 grille frames are constructed from strips of softwood; therefore, no Masonite.
Sidenote: my own observations have shown that the AR-4 cloth is slightly less dense (threads per inch) than what I've encountered with AR-4x's and later models, suggesting that perhaps the original is not authentically replaceable.
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Wow, both of you guys have "new" AR-4's that appear to have never been opened, and IMO, the wear and tear of each pair is minimal and all fully restorable. And yes, both pairs appear to have grille cloths in a condition which is definitely good enough to first attempt cleaning and restoration before even considering cloth replacement.
Plenty of AR-4 info in these threads to answer a few questions and get up to speed.
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Hi RobT, that's a very nice find. I fully agree with Lakecat - - - in present state, they are not good for much unless you restore their functionality, and they are also overdue for a cosmetic facelift. Your suspicions about problem areas are most likely correct - - - work slowly and take great care finding and removing the staples - - a dental pick and a pair of needle nose pliers come in very handy for this task. It's not too difficult. Also, take care removing the woofers - - the cones and surrounds can be a little bit delicate.
I have two pairs of AR-4's, including this one pair whose s/n's straddle your pair (XX105 and XX242). They looked nearly identical to yours, and underneath the grilles was 50 years of dust accumulation, as shown. The pots will require attention, and the caps (6uF) should most likely be replaced. Cabinets can be spruced up and the grilles can be refreshed, and eventually you'll have a terrific pair of rare great-sounding, vintage speakers. If I can locate the threads for my projects, I'll try to do so for you.
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25 minutes ago, Phxjohn said:
the original tweeters but then, if the output was too low, I would not be happy
Yes, I should have clarified that my statement was about original tweeters which experience diminishing output. Once that option finally expires, many of us are grateful to the clever restorers (chris 1, etc.) and experienced researchers and technicians (RoyC, Carl, and many others) who provide us with suitable suggestions for maintaining the HF performance of these Classics. After a successful transplant, I suspect that the max setting for the tweeter control may not be so common.
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18 minutes ago, Phxjohn said:
I am one of those who thinks the 1.5 inch midrange dome is incredible. I will never understand why someone would bypass the level controls for the midrange....
Well said.... Ditto from me.
I could say pretty much the same thing about tweeter controls, but I also do realize that many people (self included) tend to set tweet pots at near maximum in order to squeeze the most out of their shy personalities.
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All of these KLH model numbers confuse me, but those two appear to be virtually identical from the exterior. Maybe, just maybe, there might be a slight revision on the inside?.....but enough to necessitate a change in model number? Despite your suspicions about the stenciled "A" on the back plate, the serial number sticker also features the "A", so there is some yet-to-be-determined differentiation between the two. You'll probably have to take a peek inside - - meanwhile here are a few threads which might offer some ideas. From this first link, I suspect what you have is the original grille cloth.
http://audiokarma.org/forums/index.php?threads/klh-22a-speaker-score.720273/
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I was only echoing your earlier enthusiasm for this Mundorf series, but in any case - - - yes, one or two simple NPE's should suffice for this type of application.
).
AR-18s speakers
in Acoustic Research
Posted
These are the dims shown on the 18s cabinet drawing.
Yeah, I think that is basically what we are discovering - - small production tweaks being made as situations evolve.
I have kind of given up trying to understand the differences in these two tweeters - - for the longest time I merely assumed that it was simply cosmetic - - one (038) had black face paint while the other (034) included a protective screen cover. Otherwise, they appear virtually indistinguishable and the magnets are the same size (2-3/8" dia), even though the parts listings show different designations for the "metalwork asembly". In the pics attached, the 034 is on left; 038 on right.
Yup, I couldn't agree more - - - this was particularly evident in several of these small two-way models from the mid 70's to early 80's.