Vladimir...The capacitor idea is attractive, but...
1. The capacitor will give you only a 6 dB filter. It will significantly impact frequencies well above where you want to make the crossover.
2. The capacitors used in a line level filter will be of much smaller value than those of a speaker level filter and can be of the highest quality for less money.
3. The 6 dB filter will cause a 90 degree phase shift. An active line level crossover with the ubiquitous four pole L/R 24dB characteristic has a 360 degree phase shift, which is back to 0 degrees.
4. Active amplification in the line level filter is just several unity gain impedance buffering stages. These are easily implemented with almost unmeasurable distortion.
5. With a capacitor you will not be able to easily experiment with different filter frequencies. You will probably want to do this. Personally, based on much experience in this matter, I go so far as to vary the X/O frequency according to the particular music I am playing, and this requires a crossover with a frequency selection knob.
I have done the capacitor thing in the past, and I think that item 1, above, is the killer. Try it by all means, but experiment with inexpensive capacitors until you decide what you want.
1. The capacitor will give you only a 6 dB filter. It will significantly impact frequencies well above where you want to make the crossover.
2. The capacitors used in a line level filter will be of much smaller value than those of a speaker level filter and can be of the highest quality for less money.
3. The 6 dB filter will cause a 90 degree phase shift. An active line level crossover with the ubiquitous four pole L/R 24dB characteristic has a 360 degree phase shift, which is back to 0 degrees.
4. Active amplification in the line level filter is just several unity gain impedance buffering stages. These are easily implemented with almost unmeasurable distortion.
5. With a capacitor you will not be able to easily experiment with different filter frequencies. You will probably want to do this. Personally, based on much experience in this matter, I go so far as to vary the X/O frequency according to the particular music I am playing, and this requires a crossover with a frequency selection knob.
I have done the capacitor thing in the past, and I think that item 1, above, is the killer. Try it by all means, but experiment with inexpensive capacitors until you decide what you want.