Are high Q (1 < 1.5) passive filters bad?

[owdi]

Is there anything inherently bad in using a high Q 2nd order passive filter? I am still new to this, and don't even know how much I don't know......

I have a dip in response between my woofer and midrange, and would like to fill it by using a high Q 2nd order high pass filter on the midrange. I need about 4db more output at 200hz, so Q would be around 1.5. The woofer has it's own amplifier, with adjustable phase, so I think I can adjust phase to match.

I considered using a BSC circuit, but was turned off by the lower efficiency and shallow slope. The drivers are powered by my receiver, so an active filter is not possible right now.

Dan

[owdi]

I modeled a Q 1.5 2nd order highpass crossover using passive crossover designer, and found a problem. Total impedance dropped from 6 ohms to below 2 ohms at the crossover frequency. That explains how the filter achieves +4db.

[Svante]

Yes, you just discovered the main reason.

Another reason may be that dips in the response often is shifted in frequency in different directions. This is especially true around the crossover frequency, but also if the dip is caused by cone break-ups. Compensating for the dip on axis, may result in a poor off axis response, worse than without the compensation.

The best way to treat dips is to find the cause and deal with that (if possible). It is often a bad idea to compensate for them with the electrical signal, in particular if the dips are narrow band.