Wanted to share my experience on how to tune the Box + XLCA2 + Amp. Disclaimer: My JL Amp has a clipping LED so it made tuning the amp a lot easier.
Make sure your equalizer settings on the MCU is completely flat when tuning your setup. I used a 0db 50Hz sine wave file to test everything to simulate maximum travel for the subwoofer. Idea is to find the max before your signal starts clipping ergo distortion.
1. Based on Travisllado's post, there doesnt seem to be any factory bass roll-off so you should turn the bass-threshold arrow on the XLCA all the way clockwise. Start by disconnecting the RCAs from the amp-XLCA2 as safety precaution. You could leave everything connected but you risk damaging/blowing the sub.
2. Find the Max setting of the XLCA2 by playing the 50Hz signal at 3/4 volume or higher. Turn the Bass Output knob on the XLCA2 until you see the maximize LED go off, then dial it a tad back until it flickers or barely off. I turned it back a little more than I should but I wanted to be safe.
3. Now that you have the max signal setting on the XLCA2 dialed in, you can now feed that signal to the amp, in my case, the JL RD500/1 which has a clipping LED. Ran the 50Hz signal through again at 3/4+ volume and turned the input sensitivity knob until i saw the clipping LED flicker, dialed it back and Voila, the tune is complete! If you dont have a clipping LED, I recommend getting at cheapo multimeter to measure the actual AC voltage coming out of the RCAs.
V=√P⋅R
so in my case (500*2)^(1/2)= 31.62V should be what I read on my multimeter from the RCAs. If you have the VADM1, itd be (320*2)^(1/2) = 25.29 V.
I listen to mostly hip hop, electronic, pop, rap, etc so my bass preference is on the "higher" side. I usually have my bass turned up to 4-5 on the equalizer at 3/4 volume. Bass is more than i need. I also get the added bonus of being able to view the clipping LED from my trunk so i know if my amp is clipping at high volumes. Happy Bumping Y'all. By far the best mod I've done so far to the car.