Sealed cabinets (acoustic suspension) are known for tight bass, although bass extension is rarely as good as with ported designs (Bass Reflex). But no free lunch here: Ports require careful engineering and making good trade offs. Very easy to have ported designs that produce wooly, bloated, very ill-defined bass.
IN BETWEEN these designs you have the resistive port. This is what the OP is doing with the pillows. You get tighter bass like sealed, but better bass extension like ported. It damps the resonance peak of the woofer due to resistive air load. It’s called an “aperiodic” loading of the woofer.
Dynaudio in the 1980s sold a resistive vent called a “Variovent”. You can Google it.
A previous poster said that the cone doesn’t return before the next signal. That statement is total BS!! Air inside the cabinet always resists the woofer cone from moving out of its center position. When it moves out, it forms a vacuum pulling the woofer cone back to center. When the cone moves into the cabinet, air resists it and wants to push the cone out to its natural center position. BS that the cone can’t or won’t be able to center itself.
IN BETWEEN these designs you have the resistive port. This is what the OP is doing with the pillows. You get tighter bass like sealed, but better bass extension like ported. It damps the resonance peak of the woofer due to resistive air load. It’s called an “aperiodic” loading of the woofer.
Dynaudio in the 1980s sold a resistive vent called a “Variovent”. You can Google it.
A previous poster said that the cone doesn’t return before the next signal. That statement is total BS!! Air inside the cabinet always resists the woofer cone from moving out of its center position. When it moves out, it forms a vacuum pulling the woofer cone back to center. When the cone moves into the cabinet, air resists it and wants to push the cone out to its natural center position. BS that the cone can’t or won’t be able to center itself.