We all know that energy is not created or lost, but transformed.
Suppose a sine wave of 100Hz in a woofer, how is the energy dissipated?
If we take the voice coil out of the magnet for example, no mechanical work is created and I can assume the electrical energy will be dissipated in form of heat.
However, if the VC is into the gap and attached to the cone, some work is produced... is the heat dissipation reduced by the same amount?
I've been crunching on this problem for a couple of nights and I can't find an answer.
On a normally functionning woofer, assuming an impedance of 8 ohms and a applied voltage of 20VAC, what amount of power (W) is dissipated as heat in the coil? the whole 50W!?
Obviously it has to be less, but what are the mechanics involved? How do we measure or calculate the mechanical (then accoustical) energy VS the heat dissipation?
Any amount of electrical current that passes through a circuit, resistive or inductive has to be dissipated in one form or the other so what is happening in a loudspeaker?
I'm asking the question because these days I'm reconing a lot of woofers and for fun I passed 13.8VDC in a E140-8 woofer voice coil just for fun (the cone was smashed but the coil was OK)
The coil was obviously out of the gap and with 13.8V DC at around 6 ohms it should (and did) dissipate a little more than 30W which caused it to be untoucheable after a couple of seconds and started smoking a while after.
I don't see how this coil could dissipate 200W or more even with heavy venting, hence my question.... where does the energy go?
Thanks