[Chas]

When the diaphragm speaker is used in a plate circuit with current flowing, generally not over 10ma. The correct polarity is when the diaphragm is pulled inward. In that orientation, a couple of things happen, the magnetic field is increased causing an increase in sensitivity, the diaphragm will rattle so it is adjusted not to.

If the polarity is reversed, over long term, the magnet is depleted, sensitivity is reduced, to reach greater sensitivity in the reversed condition the diaphragm would have to move closer.

Under the correct pull-in current flow conditions the terminal that is to B+ is identified, RED or "+" any identified tinsel cord will have a red or other marker thread for B+.

Gaskets that support the diaphragm are almost always either hardened or missing, without the gaskets buzzing will occur despite polarity.

If the radio to be used with this type of speaker has a 71a output tube, then the horn speaker is couples with a 1 mf cap and a 30hy choke to B+. A period correct audio output transformer would work as well.

Not all horn speakers use the single ended diaphragm, others will use a diaphragm pin driven "motor" these are not polarity sensitive, the diaphragm may be metal, or in some Baldwins, mica. A mica diaphragm in good condition is much more "fuller" in tone.

GL

Chas