[apk919]

Complete and road tested... I'm a very happy camper. Do you want to hear music with the windows down at 60 mph? No problem. You'll have to use the tach to determine shift points though... Frankly I haven't turned it up loud enough to make the amp or speakers distort... it's just too loud. No problem with amp overheating or shutdown. I stopped by the custom car audio installer where I bought the amp and sub, as per the owner's request, and he gave me a huge thumbs up (he does some seriously trick installs himself, so I felt pretty good about this).

A few notes about amp/head unit settings...

Alpine 9820 Head Unit:

1) Subwoofer OFF. There's an option to change the rear preamp out to subwoofer out. The head unit tries to do some low pass filtering and also provide level control through the tone/balance menu. I'd rather set the levels and crossover through the amp.

2) Power OFF. This turns the head unit's power amps off... I assume that since this reduces the load on the internal power supply, it means the preamp outputs will have better fidelity.

3) MX Mode OFF. What on earth is this anyway? Some sort of "loudness" processor. Yuck.

4) Tone Control to DEF (defeat). Disables all the tone controls, and MX Mode. I suppose this overrides 3) above anyway.

Alpine PDX-4.150

Channels 1 & 2 (Focal front and back speakers): Since the fronts and backs are in parallel, there's currently no way to set front/back balance. That's OK, it sounds perfect to me. I suppose a high wattage L-pad (or high wattage resistors) could be used in series with the direction that needs to be attenuated. The amp gain is set to nominal, filter to HP (high pass), and the crossover to ~100Hz.

Channels 3 & 4 (Stealthbox subwoofer): Amp gain is set to nominal, filter to LP (low pass), crossover set to ~100Hz, input channel to 3/4.

This is what I've come up with in a few hours of playing around. I may try to get some audio reference sources, measure levels with my dB meter and try for something more scientific. Or, I may just drive around and enjoy it!!!

Pic 1) Finished shot of the Stealthbox.

Pic 2) Settings on the amp.