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jviss

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Posts posted by jviss

  3. AR4x Crossover Rebuild Check

    in Acoustic Research

    Posted · Edited by jviss
    more details

    Two pics.  Note in the first, "as found" pic, there was a strip of butyl rubber, same material as used to seal the woofer to the cab, over the metal clip that holds the pot together:

    AR4xFXI76356insideasfound.thumb.jpg.a583e88ab098a255133a8062dc15c3dc.jpg

    After update:

    image.thumb.jpeg.c3008fbef71c694c5f1b7c478667267e.jpeg

    I know, it's no big deal, but it was exciting for me!  Ha, ha.  It took me like 5 tries to properly staple those tie wraps for the cap.  :)

    The biggest deal was cleaning the pot: removing the verdigris, polishing the contacts, etc.  Very satisfying when completed.  

    Oh, by the way this is speaker serial number FXI76356.  I'm not sure if that third character is the letter "I," or the number "1."  The date code on the woofer is March 13, 1966.

     

     

  4. AR4x Crossover Rebuild Check

    in Acoustic Research

    Posted

    I just did my first 4x. I found the same layout as @ra.ra documented.  

    Replaced the cap with a Dayton 20µF 250V polypropylene film cap. 

    I refurbished the pot, which was severely corroded.  I soaked the parts in vinegar for a bit, then had to resort to the Dremel with a tiny nylon brush to clean that center conductor.  Lubed with Deoxit-5 as I couldn't find my dielectric grease.  Works, measures 16Ω total.  

    I cleaned the solder off the woofer terminals with solder wick and then fitted push-on spade terminals to the wires to ease assembly.  

    The tweeter works now, but it seems a bit weak to me.  Could be the source material I'm playing. 

    I'll post pics in a bit. 

     

  7. How To Test Drivers On The Bench

    in Acoustic Research

    Posted

    17 hours ago, RoyC said:

    Yes, and yes. You most likely have 4 functional tweeters. The pots/level controls are the usual culprits.

    Thank you!  And Merry Christmas to you and to all the forum members.

    I'm listening now, two pair of AR 4x speakers going at once, driven by my recently resurrected Pioneer SX-424 receiver.  I think that long neglected speakers "loosen up" with exercise.  :)

     

  8. How To Test Drivers On The Bench

    in Acoustic Research

    Posted

    On 12/22/2023 at 4:39 PM, RoyC said:

    And in the case of 4x tweeters it is very hard to find any functional used originals at all.

    Oh, wow, is that so?  You mean, used originals that have been pulled form cabinets?  I have at least two functional ones, maybe four, depending on whether the tweeters or crossovers are at fault in two cabs.  

     

  11. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    Oh, interesting, @Aadams, thank you!

    Note that, as I'm sure you're aware, aida cloth can be linen, too.  I know some they mix with synthetics, etc., but the one I have is all linen.  

    I just dyed a sample with tea (Lipton :) ) and it's not indistinguishable in color from the original cloth.  

    I'll try to make some close-up pics of what I have.  I have to dig out the DSLR with the macro lens, etc.; I can't find anything since I moved!  

    I also have a binocular microscope, as I mentioned previously, but I don't recall what I did with the camera adapter (which dropped into one eyepiece socket).

     

     

  13. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    That's O.K., it doesn't really matter.  I'm not going for a museum-quality restoration of these, I just want something that looks good and sounds good.  Based on the original cloth I have (and I know it's original as my father bought these new, and I am aware of the chain of custody and what wasn't done since), the aida cloth I bought is much, muc closer in weight and weave than the 28 ct. linen recommended.  And, it's easier to work with.  It's lighter in color, like a bleached linen.  If I wanted I guess I could dye it with tea.  I might try that with a swatch and see how it looks.  

    I wish I had access to my engineering school's anechoic chamber, I could measure the effects of the various grill cloths!  Wouldn't that be cool?  :)

    Yes, ditto on the staples!  The originals were definitely more like SF13's or JT-21's than T-50's.  Probably just regular old desk staples!  

  14. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    2 minutes ago, Aadams said:

    Re thread count of Aida vs the usual Wiechelt needlework linen.  Aida is constructed primarily to make it easy for cross stitching which is why every second thread has a prominent hole. Needlework linen is for traditional specialty needlework where stitches may span a single thread of fabric.   Aida 14 is equivalent to 28 count linen.  Aida 28 is equivalent to 56 count linen.

    8 count Aida is close to 16 count linen. 

    Adams

    Interesting, thank you.  

  15. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    42 minutes ago, JKent said:

    Aida was never recommended by anyone that I know of. The Weichelt lambswool linen we used for years was not aida cloth 

    I'm sorry, but I have seen posts here referring to it as Aida cloth, and, indeed, seen references online for it described as such.  While they apparently don't offer the 18ct. product any longer, Wechert does offer the 20ct., and I believe they call it aida.  

    But, no matter, whatever works.  I'm not necessarily going for an exact match in looks, but I don't want to upset the sound quality.  It seems to me a more open weave, i.e., 16 or 18 as opposed to 28, will be more acoustically transparent.  

  16. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted · Edited by jviss
    more info

    20 minutes ago, JKent said:

    I use an electric or manual T-50. My point was the pneumatic is probably too powerful. 
    I use Monel staples because the originals were often rusted and with all this work why not go for the best quality. But of course you are right Roy—stainless is not required. 

    I have a manual T-50, too.  In fact, I may have a "stapler problem" - I have six of them!  Four are for T-50: an electric, pneumatic, manual (hand squeeze), and hammer stapler; then a special T-59 cable stapler, and a "Littleshooter," that takes JT-21 staples (not to mention my numerous desk staplers).  The JT-21 is the closest to the original staples.  I have found the T-50's too big and thick, even using the manual stapler.  But then, your mileage may vary, as they say!  

    I wasn't aware of monel staples; I'll have to look into them.  'Though I don't suspect that in my environment, even by the sea, that regular staples pose a corrosion risk.  The originals fared just fine for 40+ years.  I see the monel are available online, like on Amazon, but not in stores around here.  Geez, I already have a huge selection or staples, including copper!  I suppose I could could use the copper ones if concerned about rust.  

    (Oh, yea, I also have one of those industrial pneumatic staples, as used for assembling boxes, etc.  Not much use in this endeavor.)

  17. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    4 hours ago, JKent said:

    Lambswool is the color. If you look at linen cross stitch cloth you will see it is quite irregular with an open weave and lot of slubs. This matches the original. Aida cloth OTOH may be linen or some other fiber, or even plastic. It has a very tight, regular weave. IMHO Aida cloth is not acoustically transparent. 

    Well, then, I'm confused, given that Aida cloth was the originally highly recommended cloth, and the cloth you recommend is a tighter weave - 28 count, as opposed to 18 or even 16.  

    My personal observation of the original cloth I have, the Aida and the 28 count linen are that the Aida is closer to the original.  

     

  18. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    53 minutes ago, JKent said:

    Again—not Aida cloth. Too tight and even looking. There are other threads that discuss alternatives to the lambswool linen.
    I have used a standard (not pneumatic) T-50 stapler with 1/4” Monel (stainless) staples.  Works well on AR-4x frames. 

    Thanks.  Being the OCD engineer that I am, I'm going to keep looking into this.  I happen to like the look of the 18 count Aida linen, and it's actually closer to the original in thickness and weight than the lambswool recommendation.  

    I might just set up my binocular microscope to count threads on the original cloth, and pull some of it apart to measure thread thickness.  :)

    I appreciate all the input and attention!

     

  20. AR4x Crossover Rebuild Check

    in Acoustic Research

    Posted

    22 minutes ago, JKent said:
    23 minutes ago, JKent said:

    For the AR grilles don’t bother with messy glue. Use 1/4” stainless staples.

    Thanks!  Yes, but I don't think they are stainless.  I saved the original staples from AR, and they are highly magnetic. 

    24 minutes ago, JKent said:

    Last step after the cloth is attached and pretty tight: spritz it with water from a spray bottle and dry with a hair dryer. It will get nice and taut. 

    Great tip!  Thanks! 

     

  21. AR4x Grill Cloth Replacement: Materials and Process

    in Acoustic Research

    Posted

    (Starting a thread for this to consolidate information on this topic, and provide some structure for an ongoing discussion.)

    Replacing the cloth on the AR4x.

    Fabric Choice:

    Several fabrics have been recommended.  The strongest recommendation seems to have been 18 Count Lambswool Aida Fabric from 123stitch.com.  Unfortunately it's no longer available.  It was recommended to me to use the Charles Craft Evenweave 28 count Irish linen needlework fabric available at Michael's.  I had previously applied the Loops & Threads™ Aida Cloth Cross Stitch Fabric, Oatmeal, also from Michael's.  

    The Charles Craft stuff is lighter in weight than the Loops & Threads, and therefore easier to work with in some ways.  

    The Loops & Threads is closer in weight and weave to the original cloth, in my subjective evaluation.  Since it's stiffer, it may also provide a bit more protection, and be more resistant to damage, than the Charles Craft stuff.  I also prefer the lighter color.  

    Summary:

    • 18 Count Lambswool Aida Fabric from 123stitch.com;
    • Charles Craft Evenweave 28 count Irish linen needlework fabric from Michael's;
    • Loops & Threads™ Aida Cloth Cross Stitch Fabric, Oatmeal from Michael's.

    Cutting:

    I use a self-healing mat and a rotary fabric cutter, with an aluminum straight edge.  This is the best way, in my opinion, 'though shears should work just fine if you are careful.

    Cutting the corners for efficient folding still eludes me.  I will post pics of how the original was cut, which I have so far not tried to emulate, but will on my next attempt.  The trick is to avoid bulges at the corners.  

    Attaching:

    I originally used my pneumatic T-50 stapler.  This is too much!  It actually damages the wood frame, and it's tough to regulate the depth to which the staples are seated.  

    Now I use a Littleshooter light-duty staple which uses No. 3 or JT-21 staples.  1/4" is the best choice for leg length.  These are much like the staples one finds in regular desk staplers, and also what was originally used by AR.  

    The lighter cloth requires that one pay more attention to stretching as it's attached, to make sure it's taught enough, and that the warp and weft aren't pulled out of alignment.  The stiffer Loops & Threads stuff is much easier to apply.  And, even though it's heavier, it doesn't seem to be too different than the lighter stuff in terms of fit into the cabinet.  

    Installation:

    I purchased a package of sticky-back general purpose Velcro squares, 7/8", with the idea that I'd apply one to each corner and one more along each side, in line with the tweeter/woofer separating member of the grill cloth frame.  I haven't done so yet, as with the new fabric the grills stay put once pushed into the recess.  

  23. AR4x Crossover Rebuild Check

    in Acoustic Research

    Posted

    Thanks, @RoyC, for the detailed response!  

    I will replace the caps, repair, refurbish, or replace the pots, and look into doping the woofer surrounds.  The cabinets look very good already!  Just have to get some glue circles off the bottoms where some self-stick felt pads were applied.  Then touch them with bronze wool and Watco.  

    I have three pair of these to do!  I hope they are all about the same vintage.  I'll have to check the serial numbers.

  24. AR4x Crossover Rebuild Check

    in Acoustic Research

    Posted

    36 minutes ago, RoyC said:

    The original crossover is easily as important as the individual drivers. It doesn't matter if an expensive off-the-shelf replacement driver is used or a generic crossover. There is much more to achieving a successful speaker "system", much less the replication of a particular design. The original design work is often overlooked.

    Roy

    O.K., I get that.  But other than the schematic, component material types, and component values, what could there be to the crossover network?  

    I recognize that my Ohmite rheostats might not be original equipment, but they're probably indiscernible from a rheostat or pot they are replacing.  Perhaps not so much if replacing an L-pad, I imagine.   

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