AR-90 and AR-9 acoustic blanket

[KlausDK]

When I see pictures of AR 9 and 90'ies, they almost always are missing the foam inserts around the tweeter and upper MR, that should complete the acoustic blanket around the three drivers in the front. I see even official pictures from AR, where they are missing. Why is that, they obviously was designed with these inserts in place? The last picture is of my 9's, I have made the inserts myself from ½" thick acoustic foam.

 

 

[xmas111]

I'm the original owner of my AR9's that I bought when they first came out and they don't have the foam inserts. They never did.

The tweeter has a thin foam pad around it but that's it. And I'm pretty sure the tweeters I replaced at one time and that's why they have the thin foam pad around them.

 

 

[ar_pro]

My original set of AR-9s from 1979 did not have the foam inserts, but my nephew's from 1981 did.

[AR surround]

My original AR-9's from 1978 also do not have the foam inserts, but my AR-90's do have them.

[PT Doug]

When we rebuilt the crossovers for my AR90 we noticed that the tweeter and the mid speakers where about -5db quieter then the mid base drivers.. we couldn't figure why?  Maybe it was because of the inserts placed in the acoustic blanket.  I took mine out. The inserts made those speakers very directional.  We left those inserts out and compensated to make all speakers flat. +/_1.5 db.  

[PT Doug]

[Stimpy]

I purchased my AR90s factory direct, around 1980, through the employee purchase program.  Both the UMR drivers and the tweeters had the foam inserts.  All pieces still show no deterioration and are in great shape.

[KlausDK]

According to Tim Holl's paper on "Engeneering the AR9", the acoustic blanket plays an important role in the design and sound quality of the AR-9 speaker:

http://www.classicspeakerpages.net/library/acoustic_research/ar-9_series_1978-1981/ar-9_series_other/engineering_the_ar-9_by_tim/

Brgds Klaus

[PT Doug]

But when does that apply; to the insert or does that apply to the entire acoustic blanket ?

[Aadams]

1 hour ago, PT Doug said:

But when does that apply; to the insert or does that apply to the entire acoustic blanket ?

The entire blanket.  The insert was not always present but the blanket was never not applied during manufacture.  Direct comparison of blanket vs no blanket sound in this thread.