No worries, Karma; We'll getcha fixed up.
Your subwoofer connection to the amp.
You want to run the voicecoils in series, bridged to the amp. Like this:
Speaker wires from the bridged outputs of the amp to one coil pos/neg, then a jumper wire on the other coil pos/neg.
That should give you the most available power without blowing anything up; Your amp's not stable bridged into 2 ohms.At the headunit
- bass boost off, bass to 'flat' (not plus or minus anything) These settings adjust the shape of the wave (distortion), which can bring you into clipping. However, you can turn them back to your preference after the filter adjustments - unless you're way out of spec, it's fine to turn 'em up a little.Now the gain.
Turn it down. You may have it set too high to compensate for the lack of volume. Also, down may look like up, because gain is typically represented as input sensitivity. 8 volts will be 'down' and 0.2 volts will be 'up'.
If you really want to get into it, you can set your gain using a multimeter;
. A little too precise for our purposes, really.Onto the filters. Try this;
On the amp, the switch should be at 'LPF'
set Subsonic filter 30Hz
set LowPass filter 90Hz
Realistically, 90 is a little on the high side, but it's a good place to start.
Subsonic filter is basically a 'highpass' filter. In other words, frequencies above your chosen setting are 'allowed to pass'. Lowpass filter is essentially the same, in reverse.
Together they form a 'bandpass' arrangement - trimming out either end of the spectrum, leaving a 'passband' of unbothered frequencies.
Your passband is simply too narrow. By choosing an SSF and LPF so close to eachother, the response +/- the chosen bandwidth is attenuated heavily, meaning your sub is hardly 'allowed' to play anything at all.
The filters are not a brick wall; The idea is that the frequency you select will be attenuated at a particular rate, and continue in a progressive slope. If you set the filters as I suggested above, you'll still be able to hear a 29Hz or 91Hz tone, but it will be much quieter.
Suggested settings and 'response graph'
Current settings and graph
With all that nailed down, play your music at a reasonable level, and turn the gain up to match the bass with the music's level. Hopefully that helps and now you can know what to expect when you make further adjustments.