About this item Port Tubes Function speaker exposes the speaker diaphragm to produce sound, and there is also vibration at the back of the speaker. After installing the port tubes,as the diameter of the port tubes is smaller than the diameter of the speaker, a relatively strong sound wave will rush out of the inverted tube. the sound waves towards the front and back of the speaker are utilized, Improve the sound quality of the speaker Dimensions Outer diameter (including Flange): 69mm/2.72", Maximum inner diameter:52.5mm/2.07", Minimum inner diameter:50mm/1.97", Length:52mm/2.05" Speaker Cabinet Vent Diameter Compatible Model:SAPR402G, fit for most brands of PA/DJ Subwoofer Bass Speaker Cabinets Box Vent, Cabinet Cutout: 2" How to Choose Size Set the cross-sectional area of the Port Tubes as S1, the effective vibration area of the bass horn as S2, and S1=(0.1-0.4) S2 is the optimal. Port Tubes length LV=(1.463 * 107R ^ 2)/(FB2VB) -1.463R, among them: LV is the length of the port tubes, R=the opening radius of the port tubes, all in inches; FB is the tuning frequency, in Hz; VB is the volume of the sound system, measured in cubic inches Package Includes 2" Speaker Port Tubes - 2Pack Speaker Cabinet Port Tubes for PA/DJ Speaker Cabinets Subwoofer Bass Reflex Tube Bass Box Vent, Compatible Model Electronics › Home Audio › Home Audio Accessories › Speaker Parts & Components › Port Tubes Electronics › Home Audio › Home Audio Accessories › Speaker Parts & Components › Port Tubes Electronics › Home Audio › Home Audio Accessories › Speaker Parts & Components › Port Tubes Electronics › Home Audio › Home Audio Accessories › Speaker Parts & Components › Port Tubes