AR-5 Insulation Insight Request

[zelgy1]

Hi all!  I am currently restoring a pair of AR-5 speakers and would like to thank all of you for the information you have shared on this site.  I have a question regarding the insulation within the units I acquired.  Please note the speakers are within 2 serial numbers of each other and date stamp on one woofer is April 4th, 1973.  I suspect this speaker is completely original.  The other speaker appears to have a replacement woofer with a PN 200004-2, which from my research should be ok.  My primary question has to do with the insulation.  The one I suspect is original was completely filled with the pieced fiberglass insulation.  The unit with the replacement woofer only had insulation behind the woofer and covering the crossover with nothing behind the tweeter and mid-range.  Is it possible the unit with replacement woofer requires less insulation or did the individual replacing the woofer skimp on the amount of insulation?    I was thinking about adding, in both speakers, fiberglass insulation batting acquired from local department store behind the tweeter/mid-range and the original batting behind the woofers.  I would appreciate your thoughts on what I should do for insulation.  Thanks in advance!

[JKent]

Welcome Zelgy

I have not worked on a 5 so maybe someone else can tell you the exact amount to use but if I were doing it I'd take the insulation out of the unmolested one, put it in a plastic bag and weigh it with my cheap fish scale, then buy a small roll of fiberglass building insulation like this to bring the other box up to the correct amount: https://www.lowes.com/pd/Owens-Corning-R-6-7-5-6-sq-ft-Unfaced-Fiberglass-Roll-Insulation-16-in-W-x-4-ft-L/50370324

Be sure to download the AR-3a restoration guide for guidance on all other aspects. The 5 is essentially a 3a with a smaller woofer. http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

btw, if the Kimpac is missing or damaged here's a great tip from RoyC: Get a roll of this low-loft batting and use a single layer behind the woofer instead of Kimpac: https://www.walmart.com/ip/Poly-Fil-Crib-Size-45-x-60-Low-Loft-Batting-1-Each/26003469Good luck

Kent

[genek]

Or you could just order Kimpak.

https://www.amazon.com/gp/aw/d/B01HNLT4NW/

[Giorgio AR]

Kent and Genek gave you great inputs!
I also agree on weighing the amount of insulation on the untouched speaker and replicating with the same amount in the non-full speaker.
Regarding Kimpac, my advice is to use hospital caps (excuse the difficulty of translation, but they are used in intensive care and operating room in hospital), I think easy to find by enterprising Chinese for a few cents.
They are elasticized in the suburbs, well adherent to the baskets, as you see in the photos, light, of minimal weight and volume and permeable to the air, not to fibbre !!                                           In the photos I have attached, the cap is in the back of a 12" woofer (of my AR LST) and they are perfect as a diameter!

Giorgio

[zelgy1]

Hi all!  I greatly appreciate the feedback!  The Kimpac was in both speakers, so I'm good there.  For those missing the Kimpac, the hospital caps are a great idea. 

Food for thought!  Rather than having one unit with batting, my plan is this: weigh the "unmolested" speaker insulation, remove the original insulation from the top half and replace with batting.  That way both speakers have the same weight and insulation material, original pieced foam in bottom behind woofer and batting in the top behind the tweeter and mid.  I'm afraid having one with batting and one filled with the original insulation may render audible differences.  I may be overthinking, but would like your thoughts.

[JKent]

Foam??

[zelgy1]

Doh! I meant pieced fiberglass insulation, not foam. 

[ra.ra]

Hi zelgy, you are correct to want to have the same type and amount of stuffing inside each cabinet, but I am having the same difficulty following this thread regarding the terms and precise materials: "pieced fiberglass", "batting", and "pieced foam".

Not unlike the sales numbers of the respective speaker models, there is much more information on this site regarding the 2ax model as opposed to the AR-5. Since the two speakers shared a common woofer and interior cabinet volume, perhaps you can locate a thread which describes the proper amount of fill used in the 2ax, and then use this as your basis for filling your AR-5's with an equal amount of new or new + original fiberglass.  

[genek]

If you remove the fiberglass from the unmolested speaker and weigh it, be sure to post the result here. I don't think we have that data on the site for the AR-5.

[zelgy1]

Just to clarify, there was no foam. Mistype on my part. They have pieced fiberglass. I weighed the fiberglass, including Kimpac, and it’s 2.05 lbs./32.8 oz. My plan will be to fill both with half original pieces fiberglass and half batting to equal the 32.8 oz. 

[genek]

Your best approach is to tear the batting into pieces about the same size as the originals and mix them together. Or just replace all the old stuffing with identical weights of new stuffing in pieces.. There may be a density difference between old and new fiberglass, and there will definitely be a density difference between pieces and batting. What you want is for both speakers to be filled uniformly and as identically as you can make them.

[JKent]

12 hours ago, zelgy1 said:

Just to clarify, there was no foam. Mistype on my part. They have pieced fiberglass. I weighed the fiberglass, including Kimpac, and it’s 2.05 lbs./32.8 oz. My plan will be to fill both with half original pieces fiberglass and half batting to equal the 32.8 oz. 

That's exactly what I did in a recent 3a restoration. http://www.classicspeakerpages.net/IP.Board/index.php?/topic/10638-another-ar-3a-restoration/

I put the new fg in the upper part and the old fg behind the woofer, as you plan to do. btw, don't drive yourself crazy trying to get exactly 32.8 oz. An ounce or so under or over won't matter. And rather than tearing the fg, which will raise some dust, I used large scissors to cut it. Another method is to lay the batt on a piece of wood, put another piece of wood on top and kneel on it to compress the fg, then cut it with a utility knife using the wood as a straight edge. This is how it's done when insulating walls.

Looking forward to photos.

 

[RoyC]

The amount of fiberglass typically found in the AR-5 is 23 to 25 ounces, with very early iterations (with the non-AR-2ax woofer) having more. The amount of fiberglass placed in the AR-5 cabinet decreased with time, just as it did with all of the early AR models. Something unique to most original AR-5's I have seen is a small piece of fiberglass placed over the Kempac just behind the woofer.

We performed many measurements with varying amounts and types of fiberglass when putting the 3a restoration guide together, and did not find significant differences in Fc or listening impressions with variations of a few ounces. Given the changes made by AR along the way, I wouldn't be concerned with the precise amount of fiberglass, just consistency between the cabinets.

Roy

 

 

[zelgy1]

Great insight from all of you and very much appreciated! RoyC, there was a small, square piece of fiberglass between the woofer and Kempac in both units. I shall give an update once project is complete. BTW, Howard’s Restor-a-Finish is a magical product. The enclosures look as good as new!