Are AR-3 midranges repairable?

[rwalton46]

I'm working on my AR-3's, and in the first one I've opened up (serial C6634), I've found that the midrange driver is basically non-functional. I've checked it with an ohmmeter, and there is continuity. But when I put a signal on the driver, I hear nothing.

In going through other posts, I've read about the tweeter "popping" its dome. Can the same thing happen to the midrange? I suspect that something like that might have happened because I can see something white between the orange dome edge and the black mounting plate. If the dome has detached from the voice coil, it that a repairable condition? Or is replacement the only option? If replacing the driver is the only way, perhaps I'll upgrade the cabinet to 3a's, or convert them to woofer-only operation. The woofers still sound great.

Thanks to all who've been providing advice and counsel on this project in a different topic.

Rick

[RoyC]

I'm working on my AR-3's, and in the first one I've opened up (serial C6634), I've found that the midrange driver is basically non-functional. I've checked it with an ohmmeter, and there is continuity. But when I put a signal on the driver, I hear nothing.

In going through other posts, I've read about the tweeter "popping" its dome. Can the same thing happen to the midrange? I suspect that something like that might have happened because I can see something white between the orange dome edge and the black mounting plate. If the dome has detached from the voice coil, it that a repairable condition? Or is replacement the only option? If replacing the driver is the only way, perhaps I'll upgrade the cabinet to 3a's, or convert them to woofer-only operation. The woofers still sound great.

Thanks to all who've been providing advice and counsel on this project in a different topic.

Rick

Rick,

The typical mode of failure with the AR-3 mid is a broken (aluminum) lead at the dome under the screen. These are very difficult to repair. Ebay's "Vintage AR" (Larry Lagace) has had some luck repairing them, but the success rate is low due to the aluminum voice coil wire, which is brittle and very difficult to work with.

Roy

[tysontom]

Rick,

The typical mode of failure with the AR-3 mid is a broken (aluminum) lead at the dome under the screen. These are very difficult to repair. Ebay's "Vintage AR" (Larry Lagace) has had some luck repairing them, but the success rate is low due to the aluminum voice coil wire, which is brittle and very difficult to work with.

Roy

Roy is right about the broken lead on the dome. The aluminum wire is brittle, and eventually the connection can break, but not always of course. I've repaired two or three, but I can assure you that the tweeter never worked or sounded the same after that. Once broken, the love is gone out of the tweeter. The "popped" dome is another problem, and more so with the super tweeter than with the midrange unit. There's really no fix for these type ailments. Essentially, these domes had a very high "rejection" rate during production, and about half were pulled off the QC line and run back through the system. You can imagine that the slightest alteration of the original configuration would have surely cause a reject back in the day, and now would be no exception. You might get one to "work," but it wouldn't be an accurate device.

The midrange has an advantage over the tweeter in that there was a fiberglass pad on top of the dome under the screen, and this counteracted the force of the fiberglass pad under the dome -- the devil that pushes out the dome in the first place. The white material on the midrange was a type of butyl substance that never completely dried, but I don't many details. The tweeter used only the clear butyl-rubber to guard against foreign material getting into the gap. In each case, this material around the periphery of the dome did not assist in the "suspension" of the dome; that was done solely by the foam in the gap, which worked very well. By the way, Villchur tried a soft dome during the experimental stages of development of the AR-3, but the soft dome did not perform nearly as well as the rigid phenolic "fried-egg" dome.

--Tom Tyson