Sealing ported enclosure to reduce boom

An in-between solution would be to change the port dimensions and thereby lower the tuning frequency. If you make the port longer, or narrower, the tuning frequency will be lowered and the bass will start to roll off higher up and more gradually. A slightly smaller diameter tube can be inserted into the port (ring the inner tube with electrical tape in two places to get a good friction fit). This smaller tube can be longer than the original port. Or, you can do it with straws, as long as they are likewise longer than the original port. Pack the straws in tightly until they deform into a honeycomb-like shape. You will probably have to remove the woofer if you do the straw-pack, so that you don't accidentally push the straws into the enclosure and end up with a pile of straws at the bottom.

How long should you make the insert? As long as possible, leaving about one diameter of clearance from enclosure walls or woofer magnets (like if the insert is 2" in diameter, you want at least 2" of clearance). If the bass is still boomy, go ahead and seal the box. If you overdid it and the bass is now too lean, the shorten the insert.

Duke
dealer/manufacturer

Thanks, Mapman!

I use a modular port system in many of my designs, and on several occasions being able to ship a longer center section to a customer has saved the day.

The ability of the end user to make this sort of adjustment is a significant, and under-appreciated, advantage of ported enclosures over most other types. There is simply too much variation on boundary reinforcement from one room to another, as well as from one location to another within a room, for a successful "one size fits all" approach to bass tuning. Imho, of course.

Duke