Tweeter offset

[Altecboy]

Why were the large advent tweeters mounted off center? I have recently mirror imaged a pair, along with some other changes. There are two ways to mount the tweeter: closer to the near edge or rotated 180 degrees and closer to the center. Why did they choose closer to the edge?

thanks for any clarification.

Les Winter

[Carlspeak]

Ofsetting the tweeter significantly reduces cabinet edge diffraction response ripples in old cabinets with sharp edges. New speaker designs with centered tweeters have rounded or severely tapered baffles. There was a period after discovery of the centered tweeter diffraction issue where most speaker builders offset the tweeters an inch or more. This went on until more sophisticated cabinet construction techniques were developed that eliminated the sharp edges one way or another.

[Altecboy]

Ofsetting the tweeter significantly reduces cabinet edge diffraction response ripples in old cabinets with sharp edges. New speaker designs with centered tweeters have rounded or severely tapered baffles. There was a period after discovery of the centered tweeter diffraction issue where most speaker builders offset the tweeters an inch or more. This went on until more sophisticated cabinet construction techniques were developed that eliminated the sharp edges one way or another.

I would have thought a layer of felt could have solved the problem. Thanks for the reply.

[Carlspeak]

Some did use felt. Spica TC-50 et al is a classic example.

Offsetting the tweeter an inch or two doesn't alter the stereo image significantly with a pair of like positioned speakers. Even AR3/a models weren't mirror imaged evem though their tweeters were about 3 1/2 inches off-center.

[Zilch]

Unless they are mirror-imaged, offsetting the tweeter significantly degrades imaging. The resultant decorrelation of the common-mode (centered) signal does enhance spaciousness, however.

They were about spaciousness, not imaging, and the advantages of not having to make, stock, and deliver two variants to each customer argued strongly in this favor -- they don't image worth a whit in stock form....