I want to create a input energy dependent frequency shunt network, which goes in parallel with a loudspeaker,
At low volumes, a certain midrange frequency should be shunted off the loudspeaker. The shunt effect should go down as the power from the amp goes up, and more midrange signal reach the loudspeaker
Edit: I should have added that it's for guitar amps: Strum the guitar lightly and the filter eats some midrange and the sound from the speaker thins; hit it hard and the lightbulb's resistance goes up exponentially, so that more midrange gets to the speaker and fattens up the sound. That's the basic idea.
At low voltage/current from the amplifier, the shunt network impedance should be low and reduce a certain audio band that reaches the speaker; let's say center f 500Hz, with a bandwidth of 300Hz , -25dB
As the energy coming from the amplifier goes up, the shunt network impedance should go up, therefore eliminating less signal and delivering more to the speaker.
The center f and bandwidth should stay the same as the energy goes up or down.
My idea is to use an LC band pass resonance network in series with a lightbulb. As the energy increases, the lightbulb heats up, resistance increases, which raises the impedance of the shunt network, and directs more energy to the loudspeaker.
A cold 100W bulb reads around 40 ohms, it goes up tenfold when hot. I imagine 3 bulbs in parallel would be 13 ohms when cold.
I realize the following issue:
The lightbulb's resistance apparently does not influences the center frequency but the bandwidth! When cold and measuring 10 ohms, the bandwidth is around 300Hz. When host and measuring 100 ohms, the bandwidth goes up to around 3000Hz (which I do not want).
The 16 ohm loudspeaker resistance will effectively be in parallel with the lightbulb resistance.
Would this deliver a stable low resistance, to keep the bandwidth in a narrow range?
Also the damping factor of the shunt network goes from 0.3 at 10 ohms, up to 3 at 100 ohms. Can someone explain the damping factor for me? Can this be translated to a total volume loss in dB? Or in voltage or current?
Is this whole thing even a possible approach or are there other issues with this idea?
Thank you for any help in advance :)