notch filters for vented boxes

[dirkwright]

I understand that notch filters are typically used when a high pass passive filter is used where the corner frequency is near the driver resonance. For woofers in vented boxes, there are two impedance resonances. I was wondering if using a notch filter on either or both of those, when no high pass filter is being used, would change the low frequency response of the loudspeaker. Would it improve the response, or do nothing? I can't seem to find any information on the web about this.

[Ron E]

Originally Posted by dirkwright

I understand that notch filters are typically used when a high pass passive filter is used where the corner frequency is near the driver resonance. For woofers in vented boxes, there are two impedance resonances. I was wondering if using a notch filter on either or both of those, when no high pass filter is being used, would change the low frequency response of the loudspeaker. Would it improve the response, or do nothing? I can't seem to find any information on the web about this.

A notch filter across the terminals will only modify impedance. For a perfect voltage source with zero output impedance, there will be no change at all.

This impedance modification is useful when crossing over near the notches, and also for reducing the slight bumps that can occur when the amplifier being used is load sensitive (high output impedance.)