On Friday, November 3, 2017 at 2:48:08 AM UTC-4, Clifford Heath wrote:
On 03/11/17 13:31, Phil Allison wrote:
Foxs Mercantile wrote:

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On 11/2/2017 8:25 PM, Clifford Heath wrote:
Also... as a filter in the power supply? Because yeah,
the one place you really want all that filtered-out
100Hz energy is in your speaker Or perhaps it was
arranged so that enough got through to the amp to
cancel it out? Crazy stuff anyhow.

Electro-dynamic speakers had the filed coil which
doubled as the power supply filter choke.
Alon with the voice coil, there was a hum-bucking coil
that canceled the residual hum from the field winding.


so this is interesting and I never thought about it before.

Any ripple in the field winding acts as a MULTIPLICATIVE or MODULATION hum.

What I mean is....consider that there is no audio for a moment applied to moving voice coil. Ripple in the field winding would not then create any audible hum because there is no second field and no force applied. The one field is modulated at 120 Hz but there is no second field from the voice coil. When audio is applied to the voice coil, the modulating field would add AM modulation to the audio.

I imagine it would not sound the same as an ordinary hum.

Anybody actually heard the hum from one of these speakers?


Mark