ra.ra
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Posts posted by ra.ra
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Hi Geoff,
Looks like you have a great pair of speakers and a very nice project here. Your documentation is excellent and enjoyable to follow. I am no expert on KLH or AR speakers, but with regards to your dates, I have had a similar observation with a pair of early AR-6's. The AR-6 is purported to have been debuted in '72 or maybe late '71, but I have a pair (serial numbers close to 04000) which have driver date stamps from Jan 1971.
So, give or take a calendar year, it makes little difference. It seems you have obtained a very fine set of speakers.
Totally agree with you about the wood screws - - - that type of particleboard is particularly crumbly and certainly would be improved with a better machine screw attachment. Keep up the good work and great posts.
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Hi David.
I suspect you've already seen this, but just in case you have not, this (long and) excellent restoration thread provides great detail on that rare KLH Twenty-Eight model. They certainly are unique loudspeakers, and like yourself, I've also become very curious about them.
http://audiokarma.org/forums/index.php?threads/klh-model-28-rare-find-restoration.577202/
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Yes, that chart seems to be one year late on those several models, and I would also add the AR-4, since I have a pair with cabinets and wax capacitors with a June 1964 date.
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I came across this simple little graphic that pretty much corresponds with Tom's early timeline from post #15. Despite the lack of specific mention of calendar years 1959 (AR-3 and 2a) and 1964 (AR-4), it seems to serve as a fairly accurate thumbnail reference for the bookshelf "Classic" models.
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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.
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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?
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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?
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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
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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.
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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
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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.
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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.
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Agreed, very nice little vid, and thanks. Academy award nomination, Documentary category?
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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)?
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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.
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"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.
1967 KLH model 5 refurbish (1967?)
in KLH
Posted
Re: woofer attachement, it'll be hard to improve on one of the very best details found in vintage AR cabinets - - - T-nuts. This pic is from that excellent AK thread on the restoration of rare KLH-28's.