Bad Speaker Box Design?

Hey Guys

This is a box that I designed and built for my 1999 Nissan Frontier King Cab. As you can see, it sits behind the driver seat. It currently holds a 12" Rockford Fosgate XLC 8 ohm driver. I am using a Fosgate Punch 250a2 for power.

I pretty much designed this box with space in mind. The sub points downward and the amp is on the other side of the box in a recessed space. Box design is not really my area of expertise, but I had this same setup in my car with a more traditional shaped box and it sounded great.

MY COMPLAINTS: when I first got this thing all hooked up the box seemed like it was little bit mushy sounding or ringy. I was also having a problem with hearing a lot of vocals and higher frequencies through the sub.  So I got some poly fill and stuffed the box. I didn't fill it up totally, but pretty close. I think I might have put in too much poly though.

These are what I think the problems are with this setup, please let me know your thoughts.

1. I am using the crossover on the amp, would a deck crossover or external active crossover be a better solution? Would that help eliminate higher frequencies better than the amp crossover, or is the amp crossover sufficient?

2. Is the sub facing the wrong direction? I am not getting the kick out of this that I want. Should the sub be facing another direction?

3. I have the amp bridged, but its a 4 ohm amp and the speaker is an 8ohm driver. Although I seem to have plenty of power. The box size is approximately 1.2 cubic feet. It is a sealed box design.

Is my design all wrong, or is it workable?

Let me know.

Thanks for any advice you can provide!

1.  If you hear high frequencies through your sub, your crossover is not set correctly.  Either the deck or amp xover should work - check your settings - but an external is usually higher quality.

2.  Not all subs can be mounted down-firing and function properly.  The RF Punch series has very low linear excursion specs (0.3") and is not a good candidate for down-firing mounting.  That being said, it will finction in this configuration, although not at peak performance.

3.  Running an 8-ohm speaker to a bridged stereo amp is fine.  The amp will operate at its 4-ohm stereo rating level.

1.2 cu ft sealed enclosure with 50% polyfill will result in a 1.32 effective enclosure volume.  That should work for this driver.  Be sure your enlosure is sealed and has no air leaks (including around the driver after mounting.) 

I suspect the ringy sound is mainly due to high frequencies in the system.  If the bass is too mushy, try removing half of your stuffing to tighten the box.  Also try elevating the driver more than you have it to allow more air flow in front of the driver. 

You may find this speaker will never sound right in a down-firing configuration.  Try rotating the enclosure so it is firing close to vertically and see if the sound quality improves and you will know.

DYohn gave you some very solid advice