This is a 7 pole passive RC PI filter. It has a low-pass cut-off of jut over 1.5 KHZ. However, as can be seen, the actual 'knee' point starts somewhat before the calculated cut-off. It shows a >100 dB reduction in signal level at 100 KHZ, although in audio we are normally concerned with the 10 KHZ point.
The end load is set at a nominal 1K and in audio circuits its not normal to talk about a standard impedance as is done with RF circuitry. You can play with the 1K load and you'll see that it doesn't have a huge effect on the performance of the filter.
Also of interest in this simulation is the ability to choose from four different points along the filter network.
