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ra.ra

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About ra.ra

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  1. ra.ra

    Ar-3a Capacitor Advice

    About film caps.....yep, I've learned at least this much from you, Roy, and your advocacy for simple and affordable replacement components has greatly helped to shape my own philosophy about sensible vintage speaker restorations. Even more so, my own experiences have confirmed that aged drivers often have significant variation, and I always appreciate when you try to drive this particular issue in these restoration discussions. Aside from this issue of capacitor ESR (re: film vs. NPE), fancy caps alone will never re-establish the diminished performance of an old and fading driver. Not dissimilarly, the adjustable controls require equal scrutiny as critical components in these circuits, and as time marches on, I'll admit that I am finding it harder to maintain confidence with these original AR pots. This is somewhat rhetorical and mostly navel-gazing, but this issue of film capacitor longevity still puzzles me a bit. Even if the robust build quality, physical size, and increased voltage ratings of contemporary film caps far exceeds the dinky little electrolytics found in many vintage speaker crossovers, where is the data to make these kind of blanket statements that seem to have become "conventional wisdom"? Albeit the Sprague Compulytics are not "dinky" or "little", but many of these seem to have retained their original values after nearly fifty (50) years. Comparatively, just where does the timeline begin to show that film caps have superior longevity? Just when did film caps debut in speaker crossovers, and where is the discussion that many (or all?) of them are still consistent performers 50 years hence?
  2. ra.ra

    Ar-3a Capacitor Advice

    We've all been cooped up with cabin fever all winter, so it's perfectly normal that we emerge from our dens with a little growling feistiness. Your previous projects have been of interest to me, so I want to throw in my $0.02 here. We all love our music, and restoring old speakers can provide great satisfaction and pride of ownership, but ........ at what price? About the capacitors - - - yikes! - - - it is indeed a big, dark, scary world out there. In other threads, I have openly outted myself as something of a cheap b*st*rd within this hobby, so I am very inclined to align myself with your "el cheapo route". Always remind yourself of what was used in the original circuit configuration...... and then ask: Will throwing dollars at your project provide superior results above and beyond the original performance? I cannot be convinced that there is good reason to pay dearly for a 150uF parallel film cap in the woofer circuit; and likewise, spending $100 for special tweeter caps seems to me like chasing unicorns. Do these type of profligate decisions result in excellent performance? Yeah, probably they do. Do they represent prudent cost-benefit choices? Nope, definitely not in my world, but your opinion and situation may be different from mine. Back to the two cents I promised: I have no doubt you'd love these speakers if you used all new electrolytics in your re-cap effort - - just like the original engineers specified. Nonetheless, these 3/4" dome tweeters are known to have diminished output over 45 years, and theoretically it can be argued that using a film cap for this application may provide a slightly increased HF output due to the film cap's lesser resistance. Also, the tweeter caps are small values and will not be costly even if you do purchase a film/poly type. Capacitors are important components in these circuits - - no doubt about that - - but I almost feel like your attention would be better focused on assessing the quality of the aged drivers and those "quite corroded" pots. Woofers might very well benefit from a re-foam or re-doping, and you should confirm that both mids and tweets are properly functioning. At the very least, the pots will require a full cleanse and re-hab. If not restorable, you'll need to find suitable replacement components. How 'bout posting some pics of these TLC 3a's?
  3. ra.ra

    DIY Supertweeters

    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?
  4. ra.ra

    AR-4X tweeter and crossover upgrade?

    Hi Harley, and welcome to the forum. First question: why are you looking to "upgrade"? Can you describe existing symptoms or future desired performance characteristics? Am not quite sure where this info is coming from, or how many variations you have documented. The 4x is a simple speaker, yet there were a few variables throughout its run. Using the typical and original woofer and tweeter, I believe there were two x-o versions, and the coil was the only variable - - I can't seem to recall what necessitated this revision... maybe stuffing quantity? A third crossover version was found in speakers using remaining AR-4 woofers. And then there was speaker dave's "improved" version - - - that was an interesting thread that resulted in a more complex crossover, but it has since received little attention in these pages. I don't think I've ever seen this HiVi tweeter applied to a 4x project, and I was surprised to see that it was a near fit to the original cabinet prep cut-out. Nonetheless, the existing T-nuts do not align with the HiVi flange screw holes, so some modification would be required. And with "heavily damaged" pots, I wish you the best, but it's all "hopes and prayers" that they might be revived.
  5. ra.ra

    Upcoming AR3a project

    Yeah, I think you're right - - - there has probably been very little feedback on performance thus far, and certainly nothing long-term. These pots appear to have a very robust build quality.......but yes, they are expen$ive.
  6. ra.ra

    Another AR3 Story for you

    Way too large for file size. If you can re-format these as ±100KB jpg files, they will load easily and have good resolution for the purpose of this forum.
  7. ra.ra

    Pot vs L pad

    Attached are the dimensions for the three versions of L-pads that are commonly available thru electronics suppliers. The 50-watt is the octagonal device. These are basically 40, 50, and 60 mm in width.
  8. ra.ra

    Upcoming AR3a project

    I'm pretty sure they've been purchased and installed and blessed in this forum not long ago. Perhaps someone with experience will chime in.
  9. ra.ra

    Vintage AR2a with vinyl finish (year)?

    As far as the vinyl wrappers that I tried to describe and showed in pic from earlier post - - yes, these can be usually removed with some attentive prying, muscular tugging, colorful cursing, and careful peeling. This vinyl is typically applied to particle board or MDF - - sometimes it peels off easily, and sometimes it is very tenacious. I've done this on two pairs of small-ish speakers - - - AR-18s' and Smaller Advents (shown in attached pic above). In both cases, I simply sanded the substrate and finished with shellac and/or satin polyurethane. IMO, already a vast visual improvement. However, in the case of Robert's AR-2a's, I think this is a case of "a picture is worth a thousand words". I was beginning to believe these were wrapped in the dreaded vinyl, but after looking at these pics from his FB page, it looks to me like it is in fact plastic laminate. Laminate is typically applied with contact cement, and if the cement bond is a strong one, trying to remove the laminate would most likely damage the underlying pine plywood substrate. The pine cabinets typically had a front nosing made of solid birch, and in this case it has been painted black. What do others see here?
  10. ra.ra

    Vintage AR2a with vinyl finish (year)?

    Robert, are you stating for sure that these speakers are covered with vinyl? Any chance you could could post some additional pics - - maybe close-up(s) of front and rear corners? It would be helpful to see your specific condition. Also, I do want to be clear that in no way was I suggesting that applying plastic laminate might be a good idea. Of course, I am unable to 100% confirm your cabinet materials, but my guesses are based on what I've seen, including this view of utility pine cabinets, where you can clearly see that all panels (four sides, front and rear) are plywood.
  11. ra.ra

    Vintage AR2a with vinyl finish (year)?

    If you follow this (long) thread started by member owlsplace, you'll see a pair of unfinished pine AR-5's that have been clad with faux-walnut plastic laminate (i.e., countertop material), and I suspect this is similar to the treatment that your cabinets have received. http://www.classicspeakerpages.net/IP.Board/index.php?/topic/8205-ar-5/&
  12. ra.ra

    Vintage AR2a with vinyl finish (year)?

    Thx, Larry, for helping to illustrate Robert's fantastic $25 find. Great looking drivers and original grille cloth...... Perhaps my description as "contact paper" was not fully accurate, but I cannot come up with a better descriptor, and I'm sticking with my initial diagnosis. The black paint on the front moulding indicates that the person that wrapped these cabinets did not wish to contend with cutting and folding the 'wrapper' over the front miter joint and extending up to the baffle board. When looking at the single rear view, the side panels fabricated from plywood indicate that the original cabinet finish was indeed "unfinished pine". As far as dating these specimens - - without serial numbers - - your best bet is to remove the woofer and begin to inspect the backside of the drivers. It is highly likely that you will find a date stamp on at least one of these. While your speakers are opened up, it's a good idea to inspect the pot controls and the capacitors - - - more pics would be helpful for additional advice. The pic attached shows both the inside and outside of a faux-walnut plasticized 'wrapper' that was stripped from a well-regarded popular vintage speaker from the early 70's. Over a particle board substrate, these adhesive sheets were applied as a single piece to cover all four sides, including the front nosing in two additional planes. This pic shows both the miter cuts and the folded edges. Robert, your speakers look to be in very good condition and you got a great deal. Too bad they are missing original labels, but you really should pay attention to inspection and maintenance of the interior components (caps and pots). As far as the visual aesthetics (faux vinyl and black paint), that's totally your call, but these 2a's have been cosmetically altered since they left the factory. Nonetheless....great deal on some great speakers!
  13. ra.ra

    DIY Supertweeters

    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.
  14. ra.ra

    Vintage AR2a with vinyl finish (year)?

    Just a wild guess, but perhaps Robert's 2a's were originally unfinished pine, and a subsequent owner opted to "jazz" them up with simulated wood vinyl contact paper? Vinyl certainly was not a factory finish - - I think the first appearance of faux-wood on AR speakers was with the AR-7 and AR-8. (re: posting images, FYI - the attached image registers as a 98KB jpeg file on my computer.)
  15. ra.ra

    Vintage AR2a with vinyl finish (year)?

    Welcome to the forum Robert. In his note, Kent meant to refer to file size of 100KB (not 100MB), and a simple jpg file format is best.
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