I don't know if they're good reasons, but speakers are ported to gain the extra efficiency and a few extra hertz to the -3db point, at the cost of poorer measured transient behavior at the low end, a more difficult impedance curve, a faster roll off from that -3db point, as well as possible port noise. I'm sure there's more to it than just that.
These are very good reasons, and a very good basic understanding of the ported enclosure. Yep, sure, you betcha!
Apart from lacking the benefits of ported designs, acoustic suspension designs have to deal with the increase in air pressure in the cabinet when the woofer moves in. Some say this can negatively affect sound quality.
This, however, is er... a backwards. I too misunderstood this for several years. The ported enclosures actually have more "spring" on the driver than a sealed enclosure. This seems very counterintuitive. Further, the associated terms for ported enclosure such as "underdamped" can create confusion. I'll try to explain.
Consider that any loudspeaker driver (in a cabinet) has spring and dampening just like a car suspension. In the case of a speaker the dampening comes from almost completely from the driver. The spring comes from the driver AND cabinet. Sure, there is pressure against the driver in a sealed enclosure. However, this pretture comes on slowly as the frequency drops. With a ported enclosure, there much more significant pressure above the tuning frequency. This creates an oversprung situation. Relatively speaking (no pun intended) the system is underdamped. The ported cabinet is more spring than damping force above the tuning frequency. With a ported cabinet there is actually more spring than in a sealed cabinet above the tuning frequency. The Q of the "idea" ported cabinet is 1. The "ideal" Q of a sealed cabinet is .707. The sealed cabinet has LESS spring with the same damping. This makes for a better damped system. It is further possible to lower the spring of the sealed system by making a larger cabinet and a "low Q" system. Such a cabinet would have even less spring with the same damping. It might have a Q of .55-.65 . Many say this is "ideal".
Typically all sealed cabinets will have a lower Q than ported cabinets. However, it is possible to give a sealed cabinet more spring by making the cabinet VERY small. This could bump the Q of the sealed cabinet above 1.
One of the very real adantages of the ported cabinet is the woofer travel. The woofer travel of a ported cabinet is more firmly limited above the tuning frequency. This is a very real consideration when max spl is considered. Ported cabinets are much easier on the driver X-max for most practical applications. Even the 1801 has a tuning frequency of about 34hz. Clearly 99.99% of music is above this 34hz. The ported cabinet enables more spl with the same driver X-max.
There are further considerations in this realm, but my remarks will hopefully suffice.
