Filter Query


2010-11-03 10:37 pm

What determines one type of filter from another in crossovers?

Is it the way the components are arranged, or their values?

I'm quite interested in a Bessel arrangement but am struggling to find any schematics (or the ones I do find all seem to be active)

I can get my head around 1st order, 2nd order and their roll off, just not how one would design one type over another

To increase the order of your filter, typically you need to add more parts. For example a first order high pass filter would be a single capacitor in series. To make it second order, you would add an inductor in parallel. 3rd order would add another series capacitor. 4th order another inductor in parallel, etc. However, note that this is just for the ideal electrical response. When you change from a resistive load to a loudspeaker which has an impedance that changes with frequency, to get a particular transfer function (such as bessel), you need to consider the frequency response and impedance of the loudspeaker along with the filter components. The acoustic transfer function is ultimately what you care about.