Philco 77

[Electronic M]

Are you sure that speaker does not have a field coil (it looks like there is cardboard in the magnet and some wires going to it)? Some field coil speakers had an extra winding on the field coil that was placed in series with the speaker...This extra winding picked up any hum from the field coil and fed it to the voice coil with reverse polarity to cancel the hum from the field coil.

If you need to sub a perm magnet speaker for a field coil type you can place a power resistor of comparable resistance to the old field coil in place of the field coil too...A choke will reduce hum more, but a resistor will work too if on a budget or in a pinch.