No. An RC filter will have to be line-level. Typically, subwoofers have built-in amplifier and a built-in active low-pass filter (in front of the amplifier).
Active filters/crossovers also work at line-level. They are built with op-amps and they can have much sharper cut-off than an RC filter.
Sometimes the subwoofer has a full active crossover built-in with high-passed line outputs for left & right active speakers.
Regular 2-way & 3-way passive speakers have an LC crossover network.
Active 2 & 3-way speakers usually have an active crossover (in front of the amplifiers) and separate amplifiers for each driver.
Most home theater receivers have powered outputs for the main/surround speakers (so these speakers are passive) but only a line-level output for the subwoofer (so the sub needs to be active/powered or have it's own separate amplifier).
The receiver also has a low-pass filter for the subwoofer output (so you don't usually need one inside the sub). The receiver also has "bass management" to optionally mix all of the bass from the other channels with the "point one" LFE channel to send ALL of the bass to the the subwoofer.
Or, you can keep the regular bass in the other channels and just use the subwoofer for the LFE (low frequency effects) channel.