OT on speaker

[C Moore]

I have 2 older combo amps that have the OT mounted on the speaker frame. I have seen it done by Fender, Magnatone, etc.
What was point of mounting it there.?
Thank You

[rdjones]

In the early days of permanent magnet speakers (ie Altec, Cinaudegraph, etc) the designs were more or less all purpose, with less of a distinction between theatre, public address, juke box and musical instrument uses.
Most larger systems had a line output transformer (70V or 500ohm) with a matching or stepdown transformer mounted on the speaker frame.
This was to minimize losses due to long speaker lines.
Since all speakers stemmed from similar designs they all had the transformer mounting pads on the frame, whether a transformer was fitted or not.

I think there may have also been some carryover from field coil speakers where there was a coil mounted on the speaker as part of it's design.

RedDog Steve

[C Moore]

I do not have your technical knowledge....but yeah, I was wondering if these early examples were part "force of habit" from the field coil days.
Thanks

[paulster]

As much as a hangover from the field coil days it was probably also to allow them to use the smallest possible chassis. Some of these old guys are crammed into tiny little chassis.

[Structo]

Also many times the field coil had double duty as the choke in the power supply.
I know the Hammond organ amp I had was like that.