I'm a little confused with subwoofer crossovers. 1. A low pass filter sends everything below a certain frequency to the driver and a high pass sends everything above a certain frequency to a driver right? 2. When using the line level inputs on a sub the crossover on a subwoofer acts as a low pass crossover ( according to my definition ) right? 3. ( here's where I'm really confused ) I had always thought that when you use the speaker level inputs on a subwoofer the crossover on the sub would act as a low pass for the subwoofer and a high pass for the other speakers depending on what you set the frequency as. But, I've seen a lot of subs with their high pass frequencies set in stone while the low pass can be changed. ...help?