I've taken some core ECE classes and can make simple filters. But, these simple filters are low quality and dont have any practical use. Can someone a little further along in the major help on how to make a good low pass filter? The reason I need one is that I am trying to filter out high frequencies that are going to a subwoofer using a reciever with out a subwoofer output. If anyone can assist me I would greatly appreciate it. Thanks in advance.