How to tune your bass in your car

Here is a tweaking process for getting the most from your subs and amp. Additional boom from the sub(s) is/are our main goal here, so will focus mainly upon that. Here we go:
Get out a few of your favorite CD's. Something with good mix and some low thump content. Dial back on the sub amp gain so there is very little sub in the mix. Turn off any bass boost features in the amp for now. May need a little later, but for now, no bass boost for now. Let's get to work 'cause BABY, it's cold outside!

1. Set the EQ functions on HU to "0" or "flat" (no cuts, no boost)
2. Pop in the CD/tape/MP3 and select your favorite cut(s) and repeat.
3. Turn up the HU volume knob until you hear some distortions from the interior stage speakers.
4. Back off on the volume until distortions are gone. Is best to get out of the car and listen with doors open from a few feet away. If you still hear a rough sound, back off on the volume a bit more.
5. Now, time to add the sub into the mix. If amp has a low Pass filter, set it in a range between 70-120 Hz. No bass boost just yet. If you have continously variable LPF, determine what sounds best in your ears, within the range noted.
6. Bring up the gain on the sub amp, until you get it thumping and hear a "little" distortion.
7. Back off on the sub gain (a wee bit) until it sound full, deep and clean.
8. If bass seems a bit lacking of punch or deep lows, a small amount of Bass Boost, can be added. (+3 to +6dB is all you should ever need here)
9. Again, if you hear the sub getting rough from distortion, back off on the gain a bit more.
10. Now, you may use the Bass Tone control on the HU to adjust your bass from the driver's seat. This works well in simple HU's. But if you have a menu driven EQ system, this is a bit more cumbersome.

That's about it and now time for a test drive to ensure you have the system well balanced and in control. However, if you still have poor bass performance or weak bass output. May try reverse the wires to the sub and see if that improves the overall affect. If it gets better, you're good to go. If it seems worse, return the sub wires to original orientation.

Finally, if you have done all these steps correctly, and the bass is still not getting much bump or louder, and your gains are maxed out, you may have to go back to the LOC's and adjust them, in conjunction with the sub amp gains.