Originally Posted by rahula7
Power compression is a long term phenomenon.
Flux modulation compression.
Yes, thermal modulation is important, but compression isn't only due to the thermal aspects of the heating of the voice coil. Granted, a great deal of the compression results from the thermal characteristics of the assembly to dissipate heat. However, another component is magnetic flux compression.
Although the typical thermal compression most discussed is more long term, the effects of magnetic compression are instantaneous. These magnetic compression distortions, can dull transients, and render reproduction as lifeless, dull and unrealistic. The issue is quite insidious because it's not an overly offensive distortion. It just seems to thins out the playback, stripping away the life and snap.
Here's more from another post I submitted on this issue;
"The magnetic issue lies in the fact that when the drummer hits the kick drum pedal, and the beater strikes the head, the signal path results in the voltage is impressed across the loudspeaker's terminals. This results in the current flow in the VC, and subsequently the driver attempts to track the signal accurately. The problem is that when current flow begins in the VC, there exists three separate, and entirely different sources of magnetic flux in the gap. The permanent magnet's flux, the signal voltage VC flux, and lastly the flux that's generated by the varying eddy currents in the pole pieces. This is the problem, the flux modulation compression.
Whereby the thermal compression effects are a function of time, the magnetic flux compression is instantaneous. Magnetic saturation of any of the motor elements needs to be entirely avoided, as it's effects instantly impact waveform shape, the peak, and peak capability."
That's my take on the issue ...