1.Why the F-1 has no separate level controls?
The SUB LEVEL adjusts the input sensitivity only. The level of SUB OUT A and B and the satellite output will be set on the connected amplifiers.
2.Why there are 2 subwoofer outputs?
This offers 2 signals with different crossover frequencies. Example:
a) SUB A limited up to 100 Hz for main subwoofer speaker
b) SUB B limited up to 50 Hz for bass vibrator under the seat
3.What is the advantage of satellite control?
Even high end small speakers with 5-6.5? woofers allow a very limited deep bass power handling only. If limited under 80-150 Hz the mechanical and electrical power handling will be much increased and the sound is better when the distortion limit is far.
4.A 6 or 12 dB active crossover is not enough?
That would be only cheaper but less effective than the 24 dB slope of the F-1. If the low pass at 80 Hz has a 12 dB slope only you can still hear lower mids. For a preferable non-directional bass you need a steep slope with variable frequency.
5.But there are high quality passive crossovers?
Yes, but at a multiple price of the F-1. A low pass at 50 Hz / 24 dB requests huge copper coils. A good high pass has to be added. If the crossover frequency must be changed all parts must be changed. At the F-1 you only turn the knobs.