Ports sill make noise and kill the sound waves at extreme volumes, but yes they will get you a 3db gain over a sealed box. A bandpass will get you 3db over a ported likewise. These are figures based on just box design. Most subwoofer drivers are made to be sealed and/or ported. Bandpass roll off very nicely for the crossover on their own, but they are very peaky for sound. Higher notes (60hz and up) are ptretty much non-existant in them. If you know how to use a parametric EQ right, then you can tame them, this is how i had one in my old car.
Slots are very turbulent btw, when was the last time you saw a square TB?
'06 Vee Dub GTI 2 door Tornado Red
- 2.0 Turbocharged, Intercooled, Direct Injected, 6 Speed DSG, Underbody Aero, 17" Classix
- Moonroof, Bi-Xenon headlamps, Interlagos Plaid Sport Seats, 6 Disc In-dash, iPod integration, GTI Monster Mats (winter)
'93 Bonneville SE Purple Pearl H4U package - picked up June 23, 2003, Traded-in June 28, 2007...