AR-11 A., B, was there a C designation?

[Pete B]

I notice mention of AR-11 A and B types here on the board, the ones I have here have a C after the model number. The crossover looks like this picture provided by r_laski:

http://www.classicspeakerpages.net/dc/user_files/335.jpg

Anyone know who designed these different versions.

The A to B version looks like a cost reduction effort with a single crossover board and simplified attenuation switching.

Anyone listen to the A and B versions side by side looking for differences?

Pete B.

[r_laski]

>>I notice mention of AR-11 A and B types here on the board, the ones I have here have a C after the model number. The crossover looks like this picture provided by r_laski:

Anyone know who designed these different versions. The A to B version looks like a cost reduction effort with a single crossover board and simplified attenuation switching. <<

The designation of “AR-11A” and “AR-11B” is NOT something that was done by AR. The designation we use has nothing to do with the SN. It is something AR-11 fans on this forum have done because during its production life AR made major changes to the *looks* of the AR-11. We informally assigned the “A” and “B” model designation to differentiate between the two different looking versions of this speaker. AR made the same changes to the other speakers in the ADD (Truth in Listening) series.

The “A” model is characterized by brass logos with black letters, the older, AR-3a/LST 200003 woofer frame, black midrange screen with yellow fiberglass, and no diffraction foam around the tweeter. Very early units had white/yellow fabric on the tweeters. Also, the “Velcro” to hold the foam grills runs completely around the recessed front baffle with the small strip between the woofer and the tweeter.

The “AR-11B” models -- Black logos with silver letters, Velcro “dots” on the front baffle to hold the foam grill, newer version 200003 woofer with silver frame and foam covering mounting flange, SN label on front baffle, silver screen over midrange with pink fiberglass, and diffraction foam on tweeter.

Also, the back of the AR-11B cabinets was painted black, AR-11A cabinets were clear coated. Some late production AR-11A’s may have had the cabinet back painted black.

A “major” change during production of the AR-11B was to change the acoustic stuffing from fiberglass to polyester. This is when the screens came off the 200003 woofer frames.

I don’t know about who the designers were. The very early AR-11A’s had the two board crossovers. The single board crossover appeared in AR-11A’s. It may have been cost cutting, but I suspect it may also have to do with Chicago Industrial and Sprague going out of business forcing AR to find a different capacitor vendor.

>> Anyone listen to the A and B versions side-by-side looking for differences? <<

Read my listening test of three AR-11s. One was a “stock” AR-11A with the two-board crossover. One was an AR-11A with single board crossover (in spec caps installed). The third was an AR-11B with poly caps.

Rich

[Pete B]

Thanks for your comments,

I did read your post and if I understand you correctly the "stock" AR-11A had aged out of spec caps. Was the AR-11A with "in spec caps" built on a new board or on the original board? I take it that the AR-11B with poly caps was laid out on a larger XO board as I think you mention in another post.

Pete B.

[r_laski]

>> ... the "stock" AR-11A had aged out of spec caps.<<

Yes, that is correct. Although not part of my test, I did listen to both AR-11A's prior to setting up the test. I did not conduct controlled listening tests, but for the listening I did, I could not distinguish any difference in "voice" between these speakers.

Until I opened up the stock AR-11A (AR-11X in the test)I had no idea how different the crossover was from the other speakers. I did not see the crossover until after the listening tests were completed. A "control" I imposed for the test.

>> Was the AR-11A with "in spec caps" built on a new board or on the original board?<<

For the listening test, the ONLY thing I did for the AR-11A with the "in spec caps" was remove and replace the original caps with "in spec" AR/Callins caps on the original board. I duplicated the assemby methods used by AR (cap lead winding on connectors and soldering) as closely as possible. Nothing else was done to the crossover.

>> I take it that the AR-11B with poly caps was laid out on a larger XO board as I think you mention in another post.<<

Correct again. The larger size of the poly caps requires crossover components be reoriented and relocated on a larger board.

Rich