Passive radiators are a good substitute for vents because they can be mass-loaded to tune for frequency and because they eliminate the possibility of vent wind noise. The inside total volume is the same as if you were tuning with a vent. Vent length versus inside cabinet dimensions is no longer an issue, and outside cabinet dimensions have to accommodate the speaker in the front and the passive radiator also in the front or on one of the sides. Passive radiators should always be two to four inches larger in diameter than the woofer. Take the passive radiator cone volume into account. Writer Bio
