My favorite loudspeaker box for bass is a sealed one; not being a fan of ports, passive radiators and transmission lines as we covered over the last few days. A sealed box simply means that the loudspeaker driver is trapped in a box with no air vents or holes in it at all.
This has the advantage of a pure output only from the front, no chuffing sounds from the port or transmission line and easier to place in the room. Disadvantages are many including the need for better drivers, more amplifier horsepower to get bass and acoustic bleed through from the back of the woofer. Still, I would not go any other direction when it comes to bass; the sonic advantages outweighing the disadvantages.
All woofers in a box roll off and produce less and less low bass as the frequency goes down. To solve that problem you can make ever larger boxes, punch holes in those boxes to relieve some of the pressure and get additional output, pump more power at those frequencies or reduce the woofer's output at higher frequencies - thus evening out the overall response.
Most sealed box loudspeakers design their crossovers to reduce the woofer's higher frequencies relative to their lower frequencies in an effort to get flat bass response; which is why the overall efficiency (sound level output per watt of input) is generally lower than other designs. We are, of course, ignoring horn types of loudspeakers in these discussions because they can actually use their horns to acoustically amplify bass - and that's another story.
My favorite bass is, as most of you know, amplified and equalized sealed box bass in its own enclosure - commonly called a subwoofer. I absolutely do NOT like subwoofers with ports - as many (read most) have such holes punched into their boxes. Yes, they are more efficient but in these days of self-amplified woofers, where you have the opportunity to equalize the response, it is far better to design a killer long throw, high output woofer driven by a proper amp than it is to go unsealed and "chuff" your way into low bass nirvana out of a port.
I know, many of you with subs have these tuned holes and I don't mean to offend, but heck, it's just my opinion after all.
Tomorrow, the Bipole.