Oh yes, the box is everything. I have always made my box to the specs given by the sub manufacturer and never been disappointed. Some points:
- Always use at least 3/4" MDF or thicker for a box.
- Never buy prefab. They are made with cheap ass particleboard and are never properly designed.
- Only mess with a box outside of the manufacturer's specs if you really know what you're doing. Even a 0.5 cubic foot variance can make a huge difference.
Bass Mechanic: A ported box will not go lower than a sealed box, quite the opposite. A ported box cannot go lower than the tuning frequency of the port you put into the box as you lose cone control below that frequency and can blow your sub. That's why many D-class amps come with a switchable subsonic filter now. Sealed boxes go way lower than a ported box, but a car's resonant frequency is generally around 40 to 45 Hz so for SPL it's a moot point. Most SQ setups use sealed boxes as you have a smoother response curve and can go a lot lower, which really helps in RTA.
-Diabolik