High Pass Filter modelled in WinISD
WinISD has a built in filter section. Access it by selecting the EQ/Filter tab and click the "Add" button to get this screen. This allows you to model the effects of different filters.
To control cone excursion below the port tuning frequency, it is often neccessary to employ a high pass filter. The design I favour is the Linkwitz-Riler 4th order filter, which is entered as follows:
The 4th order filter has a Q of 0.5 - if you enter any other value, WinISD will ignore it.
To achieve control of excursion without compromising SPL more than neccessary, try different values for the Cutoff frequency. Here is a graph of the "Sidewinder" setup, showing how excursion changes with filter design frequency. Xmax is the thin red horizontal line at 9mm
In this example, the blue graph is the one which achieves a maximum excursion of Xmax + 10%
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