Another AR cabinet "stuffing" question...

[Anthonyv62]

 

What is the best way to stuff an AR speaker cabinet? 

The "stuffing" in my pair of 4X speakers (serial FX74040, FX74072) was removed back in 2001 when I planned to begin working on them. After all this time stored away in small trash bags, that material (Rockwool?) is unusable. However, before I stored it away, I did record the weight from each speaker - 17.53 and 17.57 ounces. The cabinets were never opened or even touched since my father bought them new in the 1960s so those weights should have been reasonably accurate when I measured them.

Last week, using white John Manville R-13 fiberglass, I carefully measured out the recommended 18 ounces for early model 4X speakers using cut pieces instead of just torn clumps resembling big balls of cotton. In order to get all 18 ounces of fiberglass inside the small 4X cabinet I had to pack the fiberglass tightly up towards the tweeter - the space down behind the woofer is kind of tight as well though not as much. With a little adjusting here-and-there I could arrange some of the fiberglass to form a "scooped out" pocket (almost like a padded chamber) behind the woofer to provide a little space so it's not pushed up against the woofer basket. I've considered maybe lessening the fiberglass amount (maybe around 12-13 ounces) but I'm not sure how 18 ounces of fiberglass should fit inside these cabinets. I don't recall the original 17 ounces of material being packed so tightly when I removed it - especially not down behind the woofer - but maybe it was.

[JKent]

Hi Anthony

I'm about to start working on my own 4x's that I purchased new in 1969: SN FX262692 & FX262765. This will actually be my 2nd restoration job on these and I "think" they had about 18oz. of fiberglass (haven't opened them lately) and #5 inductor coils. I recently bought a pair of cabinets with no drivers: SN 368908 and 368196. They still had the original stuffing and crossovers and both of those had approximately 12 oz. of clumpy yellow fiberglass.

Many years ago our friend John O'Hanlon (editor of the AR-3a restoration guide) wrote: 

"Roy C. and I have been comparing notes on AR-4x details. It would appear that early AR-4x, say before about serial 290,xxx (mid-to-late 1969), used AR-#4 inductor (0.88 mH) and contained 17 oz fiberglass stuffing. The later AR-4x used AR-#5 inductor (1.2 mH) and 11 oz of fiberglass stuffing."

A recent exchange with Roy he told me earlier speakers had 17-20oz. of fiberglass while later ones (after SN 293977) had 11 or 12 oz. Apparently the engineers at AR had decided the 4x was over-damped and reduced the amount of fg. I will put 11 oz. in mine. btw, the precise weight does not seem to matter much but based on Roy's expertise I'd suggest taking out 6-8oz from each cabinet.

Kent

[Anthonyv62]

Thanks for the information and suggestion Kent. I think I've read almost everything posted on this great website and discussion forum about the subject, so I appreciate any help that make things easier to understand.

Like I said, I've considered reducing the amount of FG to around 12 or 13 oz so hopefully taking out 6-8 oz (as you suggested) might be a better option regardless of the recommended 17-18 oz used on early 4X's (# 4 inductors) like mine. 18 oz of stuffing in a 4X cabinet just seems like too much.  

 

[Illf8ed]

Anthony,

I used foam acoustic tiles glued with contact adhesive to the inside walls on my ESS rock monitor speakers.  This was suggested by a forum member.  Very good sound results.