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What is the proper way to stuff the cabinet with fiberglass?

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I am re-assembling an AR2AX speaker and I would like to know the proper way to fill the cabinet with fiberglass.

1. Cover all walls inside the cabinet with at least 1 layer of fiberglass.

First, I am not sure there is enough glass to cover all the walls inside of the cabinet. Second, I am afraid that the fiberglass matt will not stay in place unless more is used in the bottom to support the top layers.

2. Surround the woofer with a thick layer of fiberglass. This means that I will only have to worry about filling half of the cabinet with glass, up to the mid and high drivers. There is enough glass matt to do this well. However, I am worry that leaving the top of the enclosure uncovered will create unwanted resonance.

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Sorry if I already mentioned this, but be SURE to read the AR3a restoration booklet. Lots of stuff there that is applicable to the 2ax.

Info on stuffing is on page 21:

http://www.classicspeakerpages.net/library...-3a_full_pd.pdf

Kent

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A 2ax with foam surround woofer should contain 20 oz of fiberglass. Tear the batting into chunks about the size of your fist and fill the cabinet (it'll come pretty close to being filled).

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A 2ax with foam surround woofer should contain 20 oz of fiberglass. Tear the batting into chunks about the size of your fist and fill the cabinet (it'll come pretty close to being filled).

Roger, that. I just had my AR2ax's open and that is the way they were. Just chunks of fiber glass stuffed in place. Make sure there are no voids, they had wrapped pieces of fiber glass around the wires coming from the coils (inducters). So I figure it was important that there be no open spaces.

Chip

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I heard it can be important not to put too much fiberglass directly behind the woofer. Try to spread it out so you have nice well for woofer :)

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I heard it can be important not to put too much fiberglass directly behind the woofer. Try to spread it out so you have nice well for woofer :)

You may be correct. But having just rehabed my AR2axs, I found the available fiber glass that it came with filled all the enclosure. Yes, there was a shallow dimple for the woofer. Put in place the cloth material and insert the woofer. The cloth keeps the fiber glass from getting into the voice coils. I found there was just enough fiber glass filling to do the job. I did not add any and as far as I could see the entire enclosure was full, even up behind the tweeter and the mid range speakers. I did not remove the fiber glass from that area.

When I removed the fiber glass I found it tightly wound around the coil (inductor) wires. So when I reinstalled it, I made sure it was wound around those bare copper wires again. I made sure there were no voids. And it filled everything up just fine.

I do not know if the enclosure had 20 ounces or 22 ounces or even 19 ounces of fiber glass, I just put what came with it back into it and it filled up the enclosure. I did not add any nor did I remove any, except for a small scrap here and there that might add up to 0.001 ounces.

The fiber glass is not structual, just filler. But it is relatively light and it was not compressed after being in there for 35 years. So again the space was filled up with fiber glass. It had not sunk down after 35 years.

Chip

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You may be correct. But having just rehabed my AR2axs, I found the available fiber glass that it came with filled all the enclosure. Yes, there was a shallow dimple for the woofer. Put in place the cloth material and insert the woofer. The cloth keeps the fiber glass from getting into the voice coils. I found there was just enough fiber glass filling to do the job. I did not add any and as far as I could see the entire enclosure was full, even up behind the tweeter and the mid range speakers. I did not remove the fiber glass from that area.

When I removed the fiber glass I found it tightly wound around the coil (inductor) wires. So when I reinstalled it, I made sure it was wound around those bare copper wires again. I made sure there were no voids. And it filled everything up just fine.

I do not know if the enclosure had 20 ounces or 22 ounces or even 19 ounces of fiber glass, I just put what came with it back into it and it filled up the enclosure. I did not add any nor did I remove any, except for a small scrap here and there that might add up to 0.001 ounces.

The fiber glass is not structual, just filler. But it is relatively light and it was not compressed after being in there for 35 years. So again the space was filled up with fiber glass. It had not sunk down after 35 years.

Chip

Hi there

The iinsulation that was wrapped around the wires and wedged under other crossove partsr. was in the early days, sulphur laden and should be replaced with a current non-sulphur fibreglass insulation in fist sized pieces.

It is important to re-use the Kapok sheet, burlap or other soft cloth to keep the insulation away from the basket openings if screening was not used.

The pots were damaged by this sulphur and should be replaced or at least serviced to clean the contact areas.

The insulation around the crossover parts was to lessen any chance of vibrations.

An ounce or two may not make any difference but at least weighing the insulation would be best.

Changing to a synthetic insulation would not be a good idea without further scientific research.

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I am re-assembling an AR2AX speaker and I would like to know the proper way to fill the cabinet with fiberglass.

As all have mentioned, Ar stuffed the early versions "uniformly." The only one I have worked on that was not stuffed uniformly was the AR-3a-Limited (the Asian version, not to be confused with the Europen Improved).) Alex Barsotti, who worked on that model, said it was not stuffed with fiberglass but with 18 ounces of the the two-diameter, red/blue polyester like that used in the improved. In particular it was to be stuffed "mainly in the woofer half of the cabinet."

Who knows, there may be a few additional unique models around?

Cheers, John

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As all have mentioned, Ar stuffed the early versions "uniformly." The only one I have worked on that was not stuffed uniformly was the AR-3a-Limited (the Asian version, not to be confused with the Europen Improved).) Alex Barsotti, who worked on that model, said it was not stuffed with fiberglass but with 18 ounces of the the two-diameter, red/blue polyester like that used in the improved. In particular it was to be stuffed "mainly in the woofer half of the cabinet."

Who knows, there may be a few additional unique models around?

Cheers, John

Don't know about sulfur problems in the insulation. My speakers, acquired new by me at the Air Force Base Exchange, when opened up for restoration had no repeat no corrosion on the pots. The filler was common fiber glass - yellow material. So what came out went back in. And yes, I acquired the speakers in 1975 - makes them 35 plus years old. Now restored, new capaciltors and new foams and they sound great.

Cheers,

Chip

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Chip, the vintage of your speakers is most likely after AR ceased using rock wool as the stuffing medium based on your description of the yellow colored FG stuffed in your speakers.

Rock wool was used a great deal early on and can be found in AR2's, 3's, 4x's and others. It has a grayish color, is clumpy with glass shot throughout and typically of higher density than the fluffly yellow FG. Below is a link to an EPA document describing the process of how rock wool was/is? made. The document indicates some versions of rock wool were treated with melamine formaldehyde. Perhaps it is the latter version made with this binder chemical that was use by AR and it off-gassed over time to attack the pots.

http://www.epa.gov/ttn/chief/ap42/ch11/final/c11s18.pdf

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It appears the rock wool stuffing was discontinued around 1969 or 1970. It is as Carl described, but more like dense chunks that were tightly stuffed into the cabinet. All cabinets with rock wool in them have the higher amounts of stuffing typical of the 1960's model versions with cloth surround woofers. It is very nasty to work with, and the one thing I always dispose of.

The later, 1970+, yellow fiberglass is shredded into wads, and more loosely stuffed than the rock wool was. It seems denser and softer than modern fiberglass, and is found in less quantity (by weight) than the rock wool in the same models.

I have never seen a cabinet equipped with an AR foam surround woofer that had rock wool in it.

BTW, Lowes has begun carrying Johns Manville fiberglass in my area. It is an off-white color and "formaldehyde free". I recently used it in a 3a restoration project and found it to be softer and easier to work with than the pink stuff. It actually seems to be a bit more like the AR yellow fiberglass. 5 small 8oz bags (5.33sq ft roll each) provided the requisite 20oz per cabinet.

http://www.lowes.com/pd_35136-1722-B777CT_...d|1%26Va%3Dtrue

Roy

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In case anyone wants to maintain maximum originality in materials, the crepe sheets that have been variously referred to over the years as "kenpac," "kapok" and various other terms was actually called Kimpak. It was a cellulose packing wadding manufactured by Kimberly-Clark that is sold today under the name "Versa-Pak" AR probably bought the stuff in big single or double-ply rolls. No idea where to get smaller lots of the stuff that thin.

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