Dating hammond transformer

Unfortunately, the converse of this was not always true.

Some skating rinks tried to economize by using a general PA system for the Hammond also.

A little thought on how a speaker operates will tell you that the cone produces a sound wave from both sides, and by the very nature of the speaker and its operation, these two sound waves are 180 degrees out of phase, which means that they will very effectively cancel each other.

If the wavelength of the soundwave is short, [less than the radius of the speaker cone] cancellation will be markedly reduced, however in the case of bass tones which have soundwaves many feet long, no bass could be produced at all unless the speaker was enclosed in a suitable cabinet to provide significant separation of these two out-of-phase sound waves.

This is a "cut in half" diagram, thus the coils are shown as tiny circles, as though you sawed the coil down the middle and looked at the actual ends of the wires that make up the various coils in the speaker.

The arrangement is such that the voice coil lies in the gap between the north and south magnet poles.

This effectively cancels the action of the slight field current ripple voltage and eliminates the otherwise noticeable resulting AC power line humming from the speaker.


In many roller skating rinks, the Hammond speaker system would also be used for the playing of records and tapes and also as a PA system.

When current flows in one direction through the voice coil, it creates a magnetic field which reacts with the field in the gap and makes the cone move slightly to the right.


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