Originally Posted by NoTLaDStyle
a properly ported box should have a moderate gain at 40-45hz, which will sound much better for rock music. 3 db hump would be quite nice at 40hz for rap & rock music
You cannot go entirely by a chart as to whether music will sound good. Not only does personal preference have a lot to do with it, cars have bumpy response gains - a cabin gain curve is just a rough aproximation. Not to mention that some songs just sound better with freq boosts in some areas.
Lastly, power handling. Some amps have a rated SN ration that is based on fractions of their full power. You may get a cleaner response graph from the box but the amp will be putting out a much more noise and possibly clipping.
I'm not talking about "sounding good" or personal preference, I'm talking about accuracy. Ported boxes will generally not reproduce sounds as accurate as a sealed box.
The acoustics of the vehicle are another factor, so if you aim the ports/speakers at the rear glass in a hatch, you have added even more boomyness. Which some people like, but it doesn't help accuracy. Glass is the enemy of accuracy.
I know phil collins (in the air tonight) really booms on a ported box in a hatchback, not what he intended.