Gain:
Gain is like a volume knob on a stereo. More you turn it up more the stereo will amplify the input signal. The problem is your input signal can exceed the amplifiers output. The signals will then clip which causes distortion and no more power out of the amp. Problem is each HU has a different output of a signal, so the amplifiers gain needs to match that input signal.
Like in my stereo in my truck, I have my gain like 15% up. That way when I reach 45-50 on my HU the amp is about maximum power. Now if I had my gain all the way up then the max I will be able to turn my HU is to about 15 or so before I reach max power output.
Input Sensitivity
Same thing as Gain.
Crossover:
Crossovers limit frequencies going to a subwoofer. Higher order like 4th order instead of 2nd order, steeper the slope is of the crossover more effective it is. Crossovers gradually reduce frequencies. For more information check out this link.
http://www.bcae1.com/xovrslop.htm
Set woofer crossovers low pass 60-100hz depending on the sub midbass etc. 80hz is a good area.
Set the high pass crossover for your speakers to the same number as your woofer typically around 80hz.
Subsonic Filter:
Now Subsonic filter is a crossover, that limits extreme low bass going to your subwoofers. if you are running sealed set it as low as possible if you are running ported set it 5-10hz bellow your tuning of your sub.
Mode/Slope
Setting the steepness of the crossover slope. See Crossover
Infrasonic Filter:
This is the same thing as Subsonic Filter. Commonly found on JL amps.
Phase:
Phase changes the relative phase of the outputs on the amplifier. This is not that helpful in most situations.
Bass Boost
This amplifies a certain frequency. Sometimes it has set, usually around 40 Hz other amps have a variable frequency rang. The higher the bass boost is set more the amplifier boost a certain frequency. In typical installations, bass boost is not recommended to be on.
Center Frequency
This is found on many JL Audio amps, it is where you want the bass boost to kick in. See EQ.
EQ
This is like a bass boost, but usually is variable. Don't worry about this.
Linear Mode
