Curious about markings on AR Woofers

[redpackman]

I've posted these pictures in a related thread on this site, but I'm still wondering. I've seen markings like this on other AR woofers. These are from an AR-6 I've just opened up, from 1972. What's with the tic-tac-toe markings on the speakers. I've been told they were for testing purposes, but how does that work?

[djcheung]

Hi there,

I have the same question about the woofers on my AR6 as well.

Best regards,

David.

[ra.ra]

The woofers on my early pair of AR-6's (serial numbers ± 04000) in the attached pic do have the ribbed cones but do not have these markings. I believe this was a factory method to add a very small amount of mass (and/or stiffness?) to the cone. Others will chime in with a more technical rationale or historic timeline. You will find examples of both versions of ribbed cones, as well as AR-6's with smooth cones. Later model woofers usually had ceramic magnets rather than alnico. There were several versions of speaker marketed as the AR-6 model with at least four different crossover networks, but I think they were all designed to similar performance specs.

I see that David in the UK has the slim profile Euro cabinet front edge, so clearly these tic-tac-toe markings were found on both sides of the Atlantic, but it is still possible that all of the drivers were manufactured here in Massachusetts.

Long before the AR-6 arrived, many of the AR-4 woofers had a similar treatment on the cone.

[djcheung]

Hi all,

My recent refoamed AR6 doesn't have the patterns on the woofers.

Best regards,

David.