These filters roll out frequencies below the set point for the filter. Vandersteen has used this approach for years with his subs. It does not increase any signal above the crossover point. It is thought that by taking the low frequency load out of the mains that they are allowed to be more dynamic and transparent and the bass ius now reproduced by the sub. It is also desirable if the mains go down to a solid 40Hz.
There is a caveat to this. One, the filter has to be of high quality and two, the set rollout point must match up with the subs upper frequency cut-off point. Also, the filter will cause a phase shift that must be compensated for. Some subs allow these changes, others don't.
This works well in theory but it has to be set up correctly.
You can use the formula 1/ 6.28 x crossover frequency x input impedance to main amp to find the value of the filter. Solder the cap between a male and female RCA and plug the interconnect in one end and the other into the amp input. Usually most filters are set somewhere around 80hz by using a capacitor of the value computed above inline with the incoming signal to the main amp. For example, if the amp had an input impedance of 100k ohms and you wanted a filter to roll off below 80hz, you would place a .02uf in parallel to the input.
There is a caveat to this. One, the filter has to be of high quality and two, the set rollout point must match up with the subs upper frequency cut-off point. Also, the filter will cause a phase shift that must be compensated for. Some subs allow these changes, others don't.
This works well in theory but it has to be set up correctly.
You can use the formula 1/ 6.28 x crossover frequency x input impedance to main amp to find the value of the filter. Solder the cap between a male and female RCA and plug the interconnect in one end and the other into the amp input. Usually most filters are set somewhere around 80hz by using a capacitor of the value computed above inline with the incoming signal to the main amp. For example, if the amp had an input impedance of 100k ohms and you wanted a filter to roll off below 80hz, you would place a .02uf in parallel to the input.