I liked the idea of a vent to let energy out of the enclosure and came up with a way that does not add a resonance to the output. The books say don’t put any material in the mouth of a port or vent because it will destroy the tuned aspect of the port/vent. Good. Destroy it. I use a slit, made with a radial arm saw, in the rear cover board, not the baffle. I clamp the board onto my radial arm saw and lower the blade where I want the slit to be. The outside of the rear cover is face down. I cover the inside of the slit with many layers of cloth to impede the air flow and destroy resonance. When properly done I can listen to what comes out the slit and it does not have recognizable sound. I don’t hear much of anything, even at high volume but I do feel pressure leaving the enclosure. I want pressure to come out, not sound. If the bass is a bit boomy, add more layers or use thicker cloth. At very high volume the pressure leaving out the slit should only move a birthday candle flame no more than the width of the flame when held next to the slit. At lower volume there should be almost no pressure leaving out the slit. This method improves the bottom end of the bass, maintains the punch of the bass when present, and relieves pressure from the enclosure when the pressure is high. I stole the idea from the zener diode.
sound is changes in pressure over very short time periods. As quickly as 20,000 'changes' per second is within the BEST human hearing.
If your port is exchanging pressure? It is producing sound. Restricting ports or 'slits' is not a new idea. My sub has 2x ports. And came with a 'plug' to change the tuning of the box. You can tune for maximum extension or maximum output. A switch is flipped on the amp at the same time as the plug is or isn't installed, so some kind of electronic change is made at the same time.
Some people with 'too much bass' will put a SOCK in their speakers port. I've never tried that!
If you are curious? Learn to MEASURE your speaker. Measuring bass is kind of tricky, so you might want to read-up on that art. You'll need a callibrated microphone AND some software, probably REW, which is free. Done properly you'll be able to see what effect your various 'tunings' have on the final sound.