Quote Originally Posted by cradeldorf View Post
Ok so here's what ran through my head, a speaker cabinet that has the ability to breathe when it needs to but not without some effort.

.......therefore a large port would give the best lows but nothing at mid range and the horns take over above that so it is removed from the equation. So my brain fart is a cabinet with a set of valves similar to a reed valve on a 2 stroke motor one to let air in and one to let air out. This would then allow the cabinet to operate like a closed cabinet when mid ranges are playing and ported when the lows kick in providing it takes some effort to open and close them. Tuning would be achieved by the amount of pressure it takes to open and close the valves.
You're describing a Helmholtz Resonator (AKA bass reflex vented alignment, acoustic low pass filter), so no valves needed and while a larger vent is more efficient it has its own pipe harmonics that can make the vent 'sing' along. At this point then, a passive radiator (PR) in lieu of a proper vent is a viable option/desirable, so would be your 'valve' so-to-speak in that it would only allow very low frequencies (VLF) to be radiated by the cab.

GM