Modelling Filter NetworksAs you probably already have guessed I am a big fan of serial network for use in loudspeaker filters. They are "component inexpensive" and offer many desirable opportunities as those found in parallel filters. The main downside to the serially coupled loudspeakers is that they are virtually impossible to design using an anaytical approach and thus an numerical approach is required. By creating a few simple mathematical equations, you can simulate the responses of different networks and I have realized a few of those using Excel spreadsheets.Screen dump from a 1st order serial filter design spreadsheet. The way of using the spreadsheets is uniquely simple: First, you type in the characteristics of your loudspeaker unit (DC resistance and voice coil inductance) and then you try out some component values for the filtering. The program depicts the resulting impedance seen by your amplifier and the electrical magnitude response of highpass, lowpass and the summed response. Bear in mind that the acoustical parameters of your loudspeakers are not included and therefore, you should carefully consider the upper rolloff of the bass and the lower rolloff of the tweeter. I prefer to cutoff the loudspeakers atleast one octave before the loudspeakers rolloff due to the distortion parameters of the loudspeaker. |
1st order w. Zobel
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Zobel networkThe Zobel network is often difficult to design accurately, simply because the loudspeaker impedance is'nt linearly dependant on the frequencyThe Zobel network is placed directly across the loudspeaker before any filtering networks. |
2nd order serial network
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