Originally Posted by
David Analog
Remove a woofer mounting screw from the box. Carefully, and in a centered manner, press in on the woofer cone. Then return the screw. Push on the woofer again. If you do not feel a difference in the resistance then the sealed enclosure is not airtight. Not being airtight compromises the bass but also effects the woofer's longevity.
Ported versus sealed? First, you want a correctly tuned ported box for a particular woofer. An off-the-shelf universal enclosure is not optimized for any given woofer. In fact, most of these enclosures are tuned at a higher frequency for more peak output (a more obvious attribute), but you lose power handling, lose deeper bass, and lose sound quality (kind of like a one note wonder). But even in the poorest version it definitely hits louder and longer.
A good bass-reflex (tuned port) sub system will give you an appreciable increase in output. The enclosure will be larger by 40% or more, sometimes much more. And if done correctly will not sound ported. In fact, the SQ can be very good.