I spent my afternoon installing the smaller Kenwood X500-1 (300W RMS mono) amplifier along with the Stinger SGN12 line output converter (requires splicing into the factory amp wiring--which is relatively simple to do), and I must say that adding a 10" subwoofer helps out with adding in the missing bottom-end that my E53 has sorely been missing. While not windows shattering bass, which I did not want from the getgo, listening to music in the car is actually quite enjoyable again.

I had upgraded my tweeters, mids, and midbass from BSW, and I thought they were a good upgrade for cleaner sound than the stock speakers. However, the midbass speakers didn't do much for bass (no improvement over the stock speakers, except for better clarity), so I ended up with building the subwoofer box that originated with Zerochief (mostly), Essam, and a few others.

The smaller Kenwood X500-1 fit in the place that my original Alpine MRP-M500 amplifier could not fit in before. I have nav, non-DSP 10 speaker radio, and a CD changer in my 2005 X5 4.4i, and with the iBus module in the same rear cargo area, it was hard to fit the Alpine amp in place (1/8" too deep). The low footprint Kenwood fits great with room to spare on 1/2" MDF mounting plate I made (see picture). This MDF plate stablizes and firmly holds the amp in place so it doesn't rattle in the trunk nor short something out.



The amp was rotated so only the low level inputs faced the spare tire (easier to remove the spare tire by a quick disconnect of the cable), and allowed me to be able to easily access and adjust the amp settings, and lastly, made for a cleaner look (hides the bulky ground, remote, power inputs and speaker outputs).



In any event, I'm extremely happy with the subwoofer addition, and once I get a bit more tweaking on the gain, crossover, and bass boost over the next few days, it should dialed in. A hint for folks who may be tuning the subwoofer--once you put in the carpeted rear cargo floor, it will attenuate your bass a bit. I tried tuning without it in place and thought I had it right where I wanted it, but once I put in the carpeted rear cargo floor, I had to turn up the gain a bit to compensate for the damping. For reference, my Kenwood settings (per my preferences and my subwoofer box): bass boost: +3db (@ 40Hz), low pass crossover: ~90 Hz), and input sensitivity (~1.6 volts)--subject to change over the next few days as I tweak the sound a little more.

Enjoy!