ra.ra
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Posts posted by ra.ra
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On 4/10/2019 at 9:28 AM, Tunedguy57 said:
I remember a post from RoyC where he wondered if AR was ever satisfied of 6 model.
I think Roy's suspicion here is probably accurate, but it has also been documented that there have been component changes in AR speaker models going all the way back to the AR-1. And let's not even apply this rationale to the "2" series, which had at least seven iterations: AR-2, 2a, 2x (two versions), 2ax (two versions), and 2xa.
As Giorgio's posts clearly illustrate, there were a variety of components used in both the AR-4x and AR-6 models. The 4x was far more consistent than the 6 in this regard, but nonetheless the 4x had more than one version, including different woofers, different badges, and different crossovers. The AR-4xa can also be found with a number of variables: cloth surround or foam surround; alnico slug magnet or square ferrite magnet; pot control or switch; front or rear-wired tweeter; fiberglass or fiberfill stuffing; and wood veneer or vinyl cabinet finish. For this discussion, it would be most helpful if you posted pics of your particular speakers so that the specific components could be properly identified and evaluated.
The entire "4" series and the AR-6's are all favorites of mine. When I got acquainted with my first pair of 6's, there were several things that really appealed to me. Although the interior cabinet volume is identical to the 4 cabinets, there was a noticeably deeper extension of LF reproduction - - very impressive bass output for an 8-inch woofer. The small 1-1/4" tweeter is also excellent - - very good dispersion and upper high end - - most notable with brushes on cymbals and violins, e.g.
I agree with the OP (jank) that the AR-4xa (or 4 or 4x....) cabinet has wonderful proportions - - it really is a handsome small speaker. But two things about the AR-6 cabinet are particularly attractive to me. The first is the shallow depth (7-1/2"), which makes this speaker truly suitable for bookshelf applications; and the second is the aspect ratio - - the relationship of width to height. I know this is going deep into nerd territory, but the ratio of height (19.5") to width (12") results in 1.625, which is visually indistinguishable from 1.618, which represents the golden ratio or golden mean or golden section. The result is a very beautiful speaker package.
https://en.wikipedia.org/wiki/Golden_ratio
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5 hours ago, AR55 said:
I know part of the difference is the dome tweeter in the 15's, but I believe the crossover has an even greater impact.
This is a great post by AR55, and I would fully agree. I'd love to find some AR-15's for the exact reasons mentioned, and it should not be too difficult or costly to find authentic AR replacement woofers.
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15 hours ago, tysontom said:
This picture is of a pre-1965 AR-2 in Birch....
Ooh-la-la.....lots of lovely blondes in this thread
, but am just curious why those AR-2's include the "a" stick pin?
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David, those look terrific - - that Baltic birch plywood is truly great material to work with, particularly with access to CNC fabrication.
This post is timely - - - just today, I had my first extended listening session with AR-12's. We had a regional swapfest meeting here in east-central MA today that included plenty of system demos, with attendees from as far away as New Jersey. GD70 brought his fully restored AR-12's accompanied by some serious electronics and I thought they were just superb. This model does not show up often, so I'm pleased to see people speaking up with appreciation for the AR-12.
Great restoration project.
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Really great work - - - what an enjoyable project! So if I understand correctly, in these two latest examples, you've basically doubled the value of the caps from your first effort, added the rotary control, and changed the rear wire terminals. Can you describe your impressions of these latest revisions? And, do you have any pics of the backside of the tweeter?
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On 3/10/2019 at 2:43 PM, JKent said:
What values would you suggest?
I wouldn't quite know how to design a suitable resistive circuit for this use - - the chief engineer in my studio workshop swears by the trial-and-error method when other options have run out.
I know many of the switched AR and KLH tweeters employ 2.5 or 3.0-ohm resistors, so I'd probably start in that vicinity. Did your tweeters come with any product literature?
And thanks for the heads-up on Albany County Fasteners - - it looks like a great catalog of parts.
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I originally misunderstood how these were meant to work, but now I get it. I appreciate the design aesthetic as much as I admire the budget cost breakdown, and for me, that's what makes Kent's solution superior to the several hundred dollar versions. (This is said, of course, with having no first-hand knowledge of the driver quality or sound performance.)
One suggestion: if you know that you prefer the 0.47uF cap setting, why not abandon the original idea of a second cap (and crossover point) and instead use the switch (with resistor) as an attenuation control (in lieu of L-pad)? And I like the idea of using the knurled nuts - - it worked well for me on this AR-18s project of mine that I displayed in this forum.
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Hey Kent, I really enjoyed reading about this project. Your results look terrific - - very nice assembly details and material choices (except for threaded rod alloy) and the overall appearance is totally professional. Just a few questions:
- does this super-tweeter get wired in series from the AR-91 terminals?
- is the switch a two-position device with a single resistor to provide two levels of output?
Great project.
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Nice work on some fabulous speakers.
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Seems like I was being overly suspicious about those cabinets - - they look like gorgeous mahogany.
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7 hours ago, samberger0357 said:
They look nice and fairly unmolested....
Of course it would be fun and exciting to find a pair of AR-1's, and if working properly, I'm sure they would sound great. But still, the primary interest these days with the AR-1 is about collectibility and, as ar_pro has noted, the cult-like obsession with the Altec drivers. With this pair, from a collectible standpoint, I would have three concerns right off-the-bat:
- the significant damage and subsequent repair of the Altec driver.
- the mystery blue wires which confirm cabinet violations and suggest circuitry revisions.
- the uncertainty of cabinet finishes - - these "look" like maybe a mahogany color, but one cabinet rear shows possible evidence of after-market finish (stain). Also, it appears that one cabinet may have sides fabricated from plywood while the other is probably Novaply. Perhaps this indicates one cabinet might be pine and the other birch?
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23 minutes ago, sarals said:
Maybe that's were the bottom octave is, tied up in those flat dust caps?
We all know about "flat" response curves, and since these all originate with the woofer at the LF end of the audio spectrum, you may be onto something new here!
The excellent documentation in this thread and your good humor are much appreciated.
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Great write-up, great photo documentation.... a real pleasure to follow this restoration project. Will be interested to hear comparative impressions with re-built original tweeters. Still, I think these AR-5's would sound even better with flat dust caps.
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1 hour ago, DavidR said:
...they retailed for $2400/pair
.......Wow...that's a lotta cabbage. Beautiful speakers, tho'....
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On 2/3/2019 at 1:11 AM, RoyC said:
....the 15 ohm .... replacement pot from AB Tech .... It first showed up in the 80's, was Japanese made....
Roy, I must have misunderstood when we previously discussed this after I pulled these pots out of some beat-up AR-3 cabinets - - - I thought they were an occasional mid-60's alternative to the typical Aetna-Pollak pots, and not an AB Tech replacement component from two decades later. Thanks for the clarification. This pair (which were unusable) had both the 15-ohm designation stamped on the backside and the Japan markings on the front.
crumpets, you've got a fine growing collection of acclaimed AR models there. Not sure what else to say if the bass output remains deficient - - - this should not be the case with properly working AR-5's - - - but you may very well notice significant improvements after cap replacement on the 5's. As many have confirmed, the Daytons are very good choices, but there's no need to use a huge and expensive ($45 each on Wagner site) poly cap for the 75uF woofer circuit.
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24 minutes ago, RoyC said:
-What appears to be typical L-pads may actually be 15 ohm replacement pots. Note the "15" on the back of the control in the photo. AR was selling replacement pots just like these in the 80's until the very early 90's. They held up quite well. Their time frame would be consistent with the Tonegen/Japanese 1210040-2a replacement woofer.
Great catch, Roy, on the coil history and that "15" marking. We've discussed this device before, but mostly with respect to early AR-3 speakers - - I had no idea this replacement pot was still lingering well into the 80's and 90's (and still it is confusingly masquerading about as a more modern L-pad).
Regarding your comment on the 040-2a woofer, are you suggesting this would have been a suitable replacement for the AR-5 in lieu of the original 004 woofer(s)? .....and without any crossover adjustment? If so, any theories about the OP's unsatisfactory bass output?
And about the two schematics - - I thought the colored schematic (very nice!, btw) might have been your creation, and I know you once corrected the resistor value, but I simply could not recall which schematic was most accurate.
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crumpets, JKent is correct, those rotary controls are not original, but some would argue that is not a bad thing. The original ceramic pots are notoriously fussy and temperamental, and those L-pad replacements are often deemed more reliable than the originals. Sometimes when using L-pads as replacements, an additional resistor is recommended, but am not sure if this notion applies to the AR-5. They should be fine to keep in your speakers, and it's nice to see that the original knobs were installed on the backside.
I think your speakers have been worked on in these areas: tweeters, crossover rotary controls, and woofers.
Those cabinets are beautiful - - - any chance they might be teak veneer? They almost look too light and golden to be walnut. My knowledge of AR-5 is limited, but attached are two good schematics: one original AR document and one with wire color designations. They show a different midrange resistor value but don't worry about that - - I think this is just an unidentified nichrome wire, which should remain as it is. Your capacitors are original, and probably all would benefit from replacement - - - the big block contains both the 24 and 72uF caps, as evidenced by three wires; the small cylinder should be 4uF.
Your tweeter (013-2) is the correct part number for AR-5, and is a later (1983) factory service replacement provided with rear-wiring tabs. Midrange driver appears original, dated from 1974, and is largely responsible for the great vocals you have mentioned.
Once again, the woofer appears to be the central issue here - - I think you may have acquired two pairs of great AR speaker models (AR-5, AR-6) where unfortunately, the original woofers were tossed because the original foams deteriorated. What you have are 040 woofers, produced by Tonegen. I believe the original 040 woofer was created for the AR-14 in the mid 70's, and then found its way into subsequent models like the AR-48s and 48b. Your diminished bass response is very possibly due to incorrect woofer. The proper woofer for the AR-5 is p/n 200004, as shown in image attached. This same woofer p/n is often found with square ceramic magnet, which delivers similar performance.
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21 hours ago, Pete B said:
I don't know if you've ever looked closely at the lead in wires to a woofer but they are often fine multistrand wrapped or braided around a fiber center. These are tinsel wires.
Hmmm.....I find this interesting - - - thx for the clarification.
Of course I have seen that type of wire in many uses and configurations, but never with the braid as shown in the center example from your link. Nonetheless, I was not aware that this constituted the definition of "tinsel", and I have been mis-using this term to identify tiny hair-thin wires, as found in the OP's tweeters. Oops....
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1 hour ago, Pete B said:
The lead in wires are not tinsel....
Sorry, Pete, but I guess I'm just not schooled enough to know the difference between "tinsel" and "lead wires.....thin as a hair.....impossible to solder". Perhaps a micrometer measurement would educate me on the differences? Please clarify.
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1 hour ago, seventy1 said:
I assumed that it provides........
Thinking about this a bit more, and I suspect you have correctly identified several very possible functional criteria. Mostly, I was surprised to see the tinsel wires threaded above the gasket, where I first thought it would be used to protect the delicate wires during assembly.
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This thread is simply a great tutorial on the surgical dissection, blood transfusion, sterile re-suture, and successful recovery of an aging patient complaining of ennui and general malaise. Really great close-up pics and descriptions - - thx again.
The de-solder and re-solder of those tiny tinsel wires to the terminals looks to me like the most delicate step. I really appreciated the tips for using a test tone during re-assembly, and to apply the new fluid directly to the VC. Any idea what the specific purpose is for that thin clear gasket?
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That's a great story - - please show us some pics of your dumpster find! The model III (both hi and low versions) is a great vintage speaker. I always enjoy seeing these Rectilinear ads that often showed a sense of humor. Pic of nude lowboy attached.
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1 hour ago, sudhir said:
Any idea how much the #200001-1 should measure?
I've got one 001 woofer on hand and it is measuring about 4.9 or 5.0 ohms DCR.
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9 minutes ago, RoyC said:
Actually the AR-5 woofer with the domed dust cap was used in very early AR-5's.
Thanks, Roy, I suspected this might be the case but could not be certain. I've never seen the domed cap on the AR-5, but the only reason I thought this might be possible is because of the multiple changes made to this driver (p/n 200004) as evidenced by the notations on the drawing in the library. The graphic depiction shows a domed cap, but under the Revisions list, there are mentions of cap changes, including one that notes a cosmetic cap, perhaps suggesting that at one point this driver had both a flat and a domed cap - - another condition I have never encountered.
, but am just curious why those AR-2's include the "a" stick pin?
I know many of the switched AR and KLH tweeters employ 2.5 or 3.0-ohm resistors, so I'd probably start in that vicinity. Did your tweeters come with any product literature?
AR 4xa or AR 6?
in Acoustic Research
Posted
Hi jank, can you post some pics of the speakers being evaluated?
Can you explain your thoughts here concerning the 4x and the 4xa? The 4xa is a very fine small loudspeaker, but it largely suffered because it was introduced at a time when AR had two other small 8-inch two-ways in their lineup (AR-6, AR-7). IMO, it's lack of distinction and popularity is principally due to poor marketing strategies, and not due to relaxed engineering standards.
When one of the tweeters in my original pair of 4x's inexplicably went silent, due to my stash of parts on-hand, my decision was to re-build this pair as modified 4xa's by fabricating adapter plates to accommodate the smaller tweeter in the original 4x tweeter hole - - - also replaced original 20uF cap with 10uF. No further changes were made, and these speakers are terrific (see pic).
I'd be interested to hear your thoughts on this, too. My understanding of this may be incorrect, but I've always thought that each version of AR-6 was intended to create an identical set of sonic characteristics, despite the significant changes in components during its years of production.
My abilities to adequately describe differences in sound are woefully insufficient, but I would tend to agree that all of my AR two-ways are unique and do exhibit subtle differences. On any given day, I might prefer the sound of pair A over pair B or pair C; but then on another day with a different power source or different musical style, I might have a completely different evaluation of the very same speakers under comparison.