ra.ra

Jeff, I love that high-tech approach to customizing the label for the AR-1w. Tom, thanks for the corrections on the speaker dating - - it certainly makes sense to have them produced with sequential model numbers as you have pointed out. Occasionally, I refer to the attached chart for a quick look-see at the general product line, and clearly this list must have several factual errors. Not only with dates, but some lesser models (i.e. AR-1x, AR-MST) are not even mentioned.

Tom, that's a great explanation and a terrific pic, thank you. That impedance change to 8-ohms is a bit of a head-scratcher, and it's difficult to imagine what the implications of this change actually sound like. It's good that you mentioned that implementing this mode does not correspond with the use of 8-ohm amplifier taps. Is that crossover also using woven fabric-wrapped hook-up wire? The crossover is interesting for the reasons you mentioned, but it occurs to me that this set-up is simply an early version of a three-way switch, not dissimilar to what showed up in AR speakers 15 to 20 years later after the A-P pot controls were abandoned. Speaking of those pots, did they first show up in the AR-3, or were they used in later versions of the AR-1? And, it's probably been explained on these pages ad nauseam, but why did the AR-3 precede the AR-2 when these early speakers were typically released sequentially? BTW, it looks like the OP's speaker might be mahogany?

Great stories from Jeff, Tom and tekno - - - thanks, all. You know you have an early AR when you see the 25 Thorndike address on the label. About that label, since it contains a whole section of irrelevant notes on High Frequency Adjustment, this is obviously a one-size-fits-all label shared with the AR-1. But still I have a question about the notes under the Amplifier Connection section and the three rear terminals. Can someone please explain the 4-ohm and 8-ohm connection notes that seem to be dependent upon the speaker placement within the room?

Regarding AR's 10" two-ways, let's not forget that the 2x had two versions (each with distinct woofer and tweeter), and both of these were preceded by the original AR-2 with its dual tweeters (at right in first pic attached). I think Tom's comment about the silicone in the AR-8 tweeter referred to grease (precursor to ferro fluid) used in the VC gap, and not a "dope" application, which I tend to think of as a topical coating for cones, dust caps or surrounds. It is quite possible that the AR-8 tweeter was unique in this way, but I have always thought of it as being the same part number that was concurrently used in the AR-4xa, AR-6 and AR-7 from the same period (second pic). Also interesting is Tom's remark that the earliest AR-8 woofer was unique regarding its greater sensitivity, which seems to be confirmed by the catalog page in post 2 which suggests a minimum power requirement of only 15 watts for the AR-8, as opposed to 20 watts for the smaller AR-6.

More info on the simple crossover. http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6921 Oops, apparently some AR-8's did have real wood veneer cabinets. Based on comments herein, I'd guess very early American AR-8's did have real veneer and even the pot control for the tweeter. http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8033 And, I assume you're asking about the larger USA AR-8 and not this cute little Euro AR-8s.

Here is one crossover pic, which suggests the woofer running full range, the single 10uF (or paralleled 5uF) caps for the tweeter, and the two 3 ohm resistors on the 3-position switch. Below is the thread where our man Roy has confirmed this. Also, the square badge is original (but with light grille cloth) and the AR-8 came in vinyl cabinet only. I have one parts list from 1975 which shows the AR-8 woofer listed separately from the AR-2ax (late), AR-5, and AR-LST-2 10" woofers, so perhaps it was tweaked a bit to accommodate the anticipated high volume levels of rock music enthusiasts, to which this speaker model was marketed. http://www.audiokarma.org/forums/showthread.php?t=490038

In a discussion of the AR-338 on AK, this comment by Ken Kantor. I think the 338's came out pretty well. I never really understood David Rich's review of them, honestly. (Technically, that is... his listening impressions are what they are.) Also, these currently for sale on CL in the OK state.

Am just attaching a few pics here, but as already mentioned by Rlowe in post 2, I'd venture to guess the AR-338 just might be a very fine small three-way - - - perhaps even a "Big Boy". It has nearly identical cabinet dimensions as the 4-series, but a far more complex crossover and updated drivers. Mentioned in a thread not long ago, but it appears they may have been manufactured in both mirrored and identical pairs. I suspect that some speaker models from this series were not big sellers - - - I've never seen a pair of 338's.

To Steve's question in post #5 - - the AR-6 had no internal bracing. Using the TOTL tweeter and UMR from the AR-9 and AR-90 in an 8" three-way would have possibly created yet another conundrum, which would be how to arrange these larger diameter drivers on the baffle board (height x width) of a smallish speaker and then balance this arrangement with the third cabinet dimension (depth) in order to arrive at an optimal internal volume for the intended woofer. Two attempts at creating an 8" three-way bookshelf speaker are shown in pics below. The first shows the Rectilinear Mini-III (18.75" x 11.75" x 9.25") atop an AR-6 (19.5" x 12" x 7.5"). I may be mistaken about this, but I think the Rect. product uses an 8" CTS woofer (which has many similar characteristics to the typical AR-4x woofer) as well as a 5" Phillips mid and a 2" Peerless (super) tweeter. They are very nice speakers but rather inefficient and rated at nominal 4 ohms. Don't know much about the second pic, which I found on a Korean website with many images of vintage AR speaker products and components. Clearly, this is a one-off custom cabinet enclosure, but it does employ all original AR drivers from the same era - - - I have no idea how this crossover was designed and/or assembled. Unfortunately with these Asian sites, even after using Google translations they still contain a good deal of indecipherable gibberish.

Great job - - that looks better in black now than it ever did in white, even when it was new! So great to see a small table radio that has tone controls, and all of the knobs appear to be identical to those used on the Advent 300 receiver. Also interesting to learn that some of these had the 5" Phillips whizzer driver. I always liked the early Advent electronics, especially that rugged 201 cassette deck, but this model 400 is one snazzy little combo. Good description of the fix - - if you have pics of the insides, always appreciated.

I had my EPI-100's opened up today, and I began thinking about this perplexing issue that Carl raised in this post about the deeply set woofers. There will be no explanation for this coming from me, but clearly this decision was intentional on the part of the speaker designers. It is well-known that this terrific little speaker was engineered and marketed as a maximum bang-for-the-buck product to go head-to-head with the other leading small two-ways of the day (AR-4x, Dynaco A25, etc.), but from a purely cost standpoint, this decision seems to contradict the economy mantra behind fabricating this model. As Carl noted, this specific woofer placement required a second layer of baffle board: material + labor = added cost. I really like these speakers, particularly my own pair that have the earliest tweeter (masonite) and woofer (rubber surround) and crossover (with tweeter pot or L-pad). The cabinets are robust with excellent veneer, and the grilles are quite decent, but the innards are where the penny-pinching shows up. Bargain-basement capacitors, cheap and inadequate spring-loaded terminals, and the thinnest internal wiring with an assortment of wirenuts and random electrical tape splices on exhibit hither and yon. How and why do these speakers sound so good? Hmmm.....must be the drivers. So, back to Carl's (and mine, now) curiosity - - if this flagship budget speaker model was aimed at undercutting the prevailing competition in terms of pricing, what was the thinking behind this extra cost to assemble the woofer in this fashion? Obviously, the original design team determined that the added performance outweighed the added cost, but can anyone explain the performance benefits?

The Q and A in posts #11 and 12 piqued my curiosity about where the OLA cabinet volume would fall compared to the AR line-up, and I was just looking into this when Roger was writing post 14. It feels a little weird to post this summary in the Advent forum, but WTH, that's where this question arose. All of these figures have been plucked from AR literature, and it is interesting to confirm that the OLA has nearly the volume of the largest AR's of this era. Classic series 1.70 cu ft (48.2 litres): AR-3a, AR-LST 1.60 cu ft (45.3 litres): OLA 1.35 cu ft (38.2 litres): AR-5, all AR-2 series, AR-LST/2 0.65 cu ft (18.5 litres): AR-6, all AR-4 series 0.35 cu ft (9.77 litres): AR-7 ADD series 1.48 cu ft (41.9 litres): AR-10pi, AR-11, AR-12, AR-14 0.64 cu ft (18.0 litres): AR-15, AR-17 0.35 cu ft (9.77 litres): AR-18

Nice write-up, Kent. I enjoyed reading about this project, and as usual, you did a really nice job with those crossovers - - I take it that the x-o panels were easily removed with four screws? I know very little about the extensive JBL line-up of speaker models, but I find it interesting that the product literature actually mentioned the bypass caps. Apparently, this was not an uncommon component found in many JBL's of a certain vintage, and I know there are an equal number of believers and detractors when it comes to this issue of bypass caps. I have to believe that JBL engineers had a strong rationale for adhering to this practice, but since I've never tried it, perhaps that explains why I am still tinkering to resolve the "complex transient waveforms" bouncing around my living room . Full disclosure: even though I tend to be firmly planted among the 'east coast' speaker brethren, I, too, have come into possession of a pair of JBL's needing not very much work in order to re-furb them. Different model, but likewise, I'll probably replace the caps and I need one replacement tweeter (LE-25). Mine are the popular L-100's, and I certainly couldn't pass them up since I was getting change back from my Hamilton, but my biggest decision will probably be whether or not to purchase/fabricate a pair of the iconic waffle foam grilles. If I do, it will not be the orange or brown - - no, no! - - - but definitely the vibrant blue.

Carl, I'm not terribly familiar with Snell, but does it look anything like this? This is the universal 8" AR replacement woofer that I have in my AR-7's. The original drawings for several 8" AR woofers show an applied substance in this area and simply call it "treatment". This issue was mentioned in this thread but did not receive any specific response. http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7897

I seem to remember some excellent work you did with a pair of AR-4xa's maybe a year or two ago, which included some interesting tweeter level controls which were unfamiliar to me. That said, I'll be very interested to see where you go with this study with these other small two-way speakers, as well as what sort of discussion arises. If I understand you correctly, you intend to install the second AR-6 crossover [version B] into AR-7 cabinets with original drivers. See attached schematics. Looking thru the various bits of published material I have collected, I see that the AR-7 had a x-o freq. at 2000Hz, and I am pretty certain this model never underwent any changes in driver selection (except that the 8" universal replacement woofer was indeed different from the factory flat-cap original). For the 4xa, I have only seen its x-o freq. reported as 1600Hz, even though this model most certainly employed at least two different woofers (cloth-alnico and foam-ceramic) throughout its production run. Not sure if the tweeter part number or construction ever changed on the 4xa. As you know, the AR-6 has a more complex history with greater variation in components throughout its production. Drivers, coils, capacitors, switches and driver phasing all appear to have been revised at various points of production. For some time I had been led to believe that these parts changes still resulted in a speaker which was designed to perform to the same engineering standards, but I can no longer be convinced of that. Different drivers, different crossover circuits and now I see different x-o frequencies. Various published documents for the AR-6 list this as: 1500Hz (1971 AR lit.); 2000Hz (1972 review); and 1800Hz (1973 and 74 AR lit.). Based on your past project, I would have thought your first inclination might be to try to adapt the AR-7 crossover more closely toward the simpler AR-4xa rather than the more complex AR-6, but nonetheless, I'll be interested to see where you go with this study.

Another month evaporates, but very little progress to report on this project. Nevertheless, other questions arise, and once again I seek advice and opinions from the collective brain trust. Woofer. As you can see, my initial intention is to use this damaged AR-7 woofer - - the cone was torn in transit due to inadequate packing (not altogether catastrophic, relatively speaking, since the matching woofer fell out en route and never arrived!). My attempt to repair the cone (with fibrous paper on backside, courtesy of sage advice from Bill Legall), is not particularly attractive but I think it just may perform satisfactorily. My question here is about 8" foams - - - I have several 8" AR woofers needing re-foam, and while I've always been very pleased with service and product from M Sound, I know that John has been challenged keeping up with customer requests. So I guess my first question is: are there other recent preferred products and vendors for foam surrounds for 8" AR woofers? Stuffing. This MST cabinet already has some FG stapled to backside, but how much more to add? Still can't believe MST cabinet volume is identical to AR-7 (see post 2), but is there a quantifiable measure for this material? More FG, or poly-fill? Capacitors. Originally, I simply assumed I would install two new polypropylene caps, but now I want to ask about polyester caps, which I understand may offer performance (due to higher ESR) which more closely complements the original speaker voicing which used NPE caps. My thoughts include something like these German ERO Roederstein (green, in pic of random assortment) caps, which I believe to have a polyester dielectric; or maybe Carli caps from Madisound?; or maybe Mallory 150 caps? Thoughts, advice greatly appreciated.

Agreed, very nice little vid, and thanks. Academy award nomination, Documentary category?

Thank you, Tom, that is the first time I have ever seen these components identified in a schematic. My sketch was almost correct - - looks like I just need to re-direct one of the 3-ohm resistor leads to the center terminal of the switch. Regarding the switch, I assume the one that the schematic suggests is a 3-position switch, as shown in the crossover pic and these rear panel views of the MST-1. If so, I'm leaning toward something like this single-pole, double-throw (SPDT) mini-toggle rated up to 6 amps. And, if I wanted to create a four-tweeter unit with the two separate crossover frequencies, would I simply add another of the same driver on the other side panel and wire it in parallel with the other side tweeter (after the 2 mfd cap)?

From viewing photos only, this is my best stab at creating a schematic for the 3-tweet MST-1, with C-1 serving all tweeters, and C-2 only for the side tweeter. Any comments on the wiring, or known values for the capacitors? 7.1.14 edit: added pic of crossover.

"Don't know nothin' 'bout no bluetooth" basically applies to me as well, but the idea of a separate mono system does have some appeal. I have been trying to learn about some of these tiny inexpensive T-amps that seem to have quite an enthusiastic following, but my knowledge of new-fangled audio gear and compatibility is seriously lacking. Re: outfitting the cabinet, I'm beginning to think about a hybrid MST - - - maybe a four-tweet version with two crossover frequencies? If that, would the super-tweets be located on the angled side panels? Any ideas on the cap values from the original MST-1? Attached is view of Scott 222-D speaker terminals. Not knowing anything about Bluetooth receiver boards, I did find this, which was quite educational. http://www.youtube.com/watch?v=z4DtZx1oxcA

A few other thoughts and pics.... Cleaned up the cabinet just a bit, and then loose-dropped in a few drivers just to generate ideas. It occurred to me that I've never seen any company literature or schematic for the 3-tweet MST (MST-1), but I am now attempting to put together a sketch for comments, based on pics I've seen of the crossover components. But still, there seems to be no information on the amount of cabinet stuffing or even the cap values for the tweeters. Not particularly germane to my particular objectives but equally curious to me, AR literature suggests that the cabinet volume of the MST is equivalent to the cab volume of the AR-7. At first I thought this couldn't be true; then I placed an AR-7 atop the MST and saw that their cabinets depths are identical and their horizontal cross sections appear to be nearly the same. But then I reconsidered again - - when the third dimension (height) is accounted for, the MST cabinet is more than 4 inches taller than the AR-7. Are these published cabinet volumes fact or fiction?

Rather long-winded here, but.... My two take-away thoughts from this experience are: 1) you just never know what might turn up in the most unexpected place, and; 2) sometimes there is comedy and tragedy within the same tale. Yesterday I was exploring a South Boston warehouse for modern furniture, and very soon thereafter stumbled upon a totally different industrial building with a hand-painted "Saturday flea market" sign leaning against the fence. Unlike so many places within urban Boston, parking was easy and available, so what the heck, let's take a look-see inside. The place was cavernous and gloomy with no natural light, and the only other things that held any attraction for me were a full set of 50's metal kitchen cabinets and a pre-owned golf club, both of which I passed on. But what really caught my attention was a lonely orphan AR-MST speaker, sitting rather uncomfortably amongst some hideous Rococo dining room hutches and buffets. Upon closer inspection, this really isn't much of a speaker to speak of.....so to speak. Curiously, this "find" seems to be an original four-tweeter MST cabinet which I am sure never left the factory as a finished product. The 3-sided hinged linen grille is present (condition: decent), as are twenty T-nuts, and the cabinet has a layer of thin fiberglass stapled to most facets of the interior. Otherwise, no drivers, no crossover components or rear panel, no wiring, no switch, no terminals or front badge. Speckled paint on backside, most likely intended for Euro market. Oops, I stand corrected by my own pics.... what I meant to say was "no original drivers". This specimen, which I did purchase (no sympathy required - - - it was almost free), had a single 8" co-axial driver which had zero screws holding it in place, flopping around like a fish in a boat, but at least it did have a long tail of attached brown lamp cord (huh?). The tweeter openings were all covered with what looked like war-zone bandages, swatches of fiberglass insulation taped over the cut-outs. Yikes!!! ...... although it's been well-documented that classic AR speakers are not particularly attractive with their clothes off, this one just might raise the bar for ugly. Appalled and aghast yet?.... but truth be told, that was actually the comedy portion. The tragedy now appears in Act II. Gleaned from rapport with the merchant, I soon learned that this semi-skeleton cabinet was a loner on the sales floor solely because it was so very fortunate to include this single "speaker". Mouth agape, jaw dropped, eyeballs rolling backward, I was informed that the other three similar (and entirely NOS, still in plastic wrap) cabinets were recently relegated to the dumpster (long gone, yep, I was willing to dive) because each of them did not possess said desirable speaker driver, and therefore, were deemed worthless. Sigh... What's past is history, so let's look to the future. The central purpose of my post here is that I am just fishing for thoughts about how I might best use this unique cabinet. I am reasonably familiar (but no expert) with the 3-tweet and 4-tweet versions of the MST, but clearly, this speaker model had its (limited) success and failure in two-channel stereo mode. With only one cabinet, there simply ain't gonna be no typical stereo with this project. My thoughts, thusfar. With a four-tweet cab, I do have more options than a three-tweet cab might offer, at least regarding tweeter placements. My limited inventory does include several versions of 8" AR woofers (cloth and foam, alnico and ceramic) as well as several 1.25" tweeters (ferro-fluid and not), so I do have some in-family drivers that will fit the baffle cut-outs and just might "play well with others". With only one cabinet, one consideration is to construct a symmetrical "center" channel which could then fit to my 60's HH Scott tube amp which does have taps for this feature. I really just don't quite know what to do with this, but I'd like to make it operable within the general spirit of the original MST products. If this center channel idea might just be a feasible notion, how might I try to fabricate this completed speaker - - - more like the 3-tweet version (two x-o frequencies) or more like the 4-tweet version (one x-o frequency)? .... or something else unique in between? Thoughts and ideas welcomed and appreciated.

I was totally unaware of JKent's post-edit in post #17 until just now, but Bingo!!!! .......... I do think he has solved this puzzle. These colorful caps are indeed small things of beauty, but really, who wants to have to decipher this code just to ascertain the microfarad value of these teeny components? I was flummoxed by the seemingly apparent lack of five stripes, but indeed they are there - - - there just happen to be two adjacent red stripes that appear to be one rather wide one. JKent's math calcs have totally convinced me - - - these Italian flag caps do indeed have a 2.2 uF value. You almost have to work from the bottom up to decipher this color code: determine the voltage and tolerance first, then figure out the capacitance with the remaining stripes. Anything that represents basil, tomato and mozzarella is always OK with me. Fortunately, I've not yet ordered a quantity of 2uF caps for this restoration, but will instead focus on purchasing 2.2uF caps if the Mullards do not measure up to snuff. Below is a bit of colorful intrigue. Pics shown, described as follows: 1. (3) "tropical fish" caps - five bands distinct 2. (3) "tropical fish" caps - five bands distinct 3. mullard color code map 4. .0022uF cap (note here that there is a triple band of red at top, then white, then red) 5. .022uF cap v.1 6. .022uF cap v.2 7. 2.2uF cap (subject of this thread, and the largest uF value in this series) At least for this pair of Mini-III's, I am now convinced that the original cap values were 2.2uF and 90uF. For more info, go here: file:///Volumes/GWA%20OFFICE/mullard%20caps/Mullard%20Magic.htm

to alkermes: I first learned of these striped Mullard caps reading a thread on AK about highboys, and my pics below show two of the three grille cloth fabrics (JKent's original off-white being the third choice) offered on Mini III's. to fisher400: your comments in post 14 make sense to me now - - this pair of speakers has the mids adhered to baffles with a stiff yellow glue (that looks similar to Titebond) instead of the flexible clear silicone that was used in my first pair. to JKent: thanks, yes, I will conduct a more serious woofer-push test when I give these a more thorough evaluation. After pulling the woofers to peek inside, I found that the original rope caulk is so crunchy (unlike similarly aged AR's I have dis-assembled) that it can no longer provide even a temporary air-tight seal, so I will have to provide a good temporary seal at the woof opening to conduct this test. Images below show two types of grille cloth, both speckled - - what I call mid-brown and dark-brown. Backside of grilles shows that mid-brown was single layer cloth, but dark-brown also had the second layer of black scrim (note here that position of tweeter has changed). Backside of cabinets depicts two minor, but obvious, differences - - in these pics, more recent speaker is on left; earlier speaker (with missing control knobs) is on right. The first notable difference is the change of speaker wire terminals. The other difference is the cabinet perimeter assembly detail. On the earlier (right) speaker, the back panel is flush with the four sides - - probably a simple rabbeted joint. On the later (left) speaker, the back panel is recessed from the four sides by about 1/4", and while this does provide a nice little finger grip for lifting the cabinet box, I think its primary purpose is to keep the rather large tone control knobs from protruding beyond any part of the wood cabinet box, which does happen in the earlier version.

This post about caps only. More thoughts later. While they will never surpass AR's as my preferred speaker manufacturer, Rectilinears seem to be the Rodney Dangerfield of 60's-70's east coast speakers - - - "they don't get no (much) respect!" But at least there are three or four of us here on CSP who seem to have an appreciation..... No question, I will be replacing the 90uF caps - - - can't seem to locate any single 90 uF NPE cap, which is fine, so am thinking about using Erse 40uF + 50uF - - - both their 6% and 10% tolerance caps seem to be superb price values (pennies!!), and are all almost the exact same dimensions. Easy-peezy parallel install. Would not know what to think of mixing NPE with the surplus polypropylenes - - - am curious, what's to gain with this method? As I've noted in other posts, I do like these 10 uF surplus caps a lot and am grateful for having had them brought to our collective attention here on CSP - - great, great value .... but really, does anyone truly know how long these will last as compared to NPE's? They do measure very accurately when new, but then, what should we expect from this little known Taiwanese manufacturer regarding longevity? I do not mean to knock these caps at all, but these thoughts are from my cynical devil's advocate voice. My experience with these caps to date has been positive, and I expect to purchase more in the future at such a bargain basement price. Despite the attractiveness of their ultra low price, my own replacement solutions are largely driven by a preference for simplicity plus a realistic understanding of my own soldering skill level. Issues of capacitor longevity aside, I remain unconvinced I'd be able to detect audible differences between film and NPE caps, even tho' I do understand the huge importance of the midrange driver in the Mini III and want to restore its function properly. Final point about the multi-cap solution: at what point does a large wad of small cap values begin to compromise the necessary internal volume of a speaker cabinet, particularly with small cabinets? About the 2 uF cap. I had originally planned to simply replace them with a good (Dayton? Erse?) film cap, but with JKent's comment about Mullards, instead I will remove and measure these before deciding on replacement. And the color coding? It does sound fairly straightforward, but there is no way I was able to come up with a value of 2uF for these caps trying to interpret the tropical fish chart.