Subwoofer Speaker Cabinet Port Tubes, 3"x3", 2 Pack 3" Diameter x 3" Length, Bottom Grid, for PA/DJ Speaker Cabinets Subwoofer Bass Reflex Tube Box Vent

[Port Tubes Function] A standard inverted speaker exposes the speaker diaphragm to produce sound, and there is also vibration at the back of the speaker. If the vibration of the speaker towards the back is also utilized, it will strengthen the sound wave and the bass. After installing the inverted tube, as the diameter of the inverted tube is smaller than the diameter of the speaker, a relatively strong sound wave will rush out of the inverted tube. In this way, the sound waves towards the front and back of the speaker are utilized, improving the sound quality of the speaker.

[Dimensions] Outer diameter (including
Flange): 93mm/ 3.66", Maximum
inner diameter: 77mm/ 3.03", Minimum
inner diameter: 74.5 mm/ 2.93", Length: 75mm/ 2.95" [Speaker Cabinet
Vent Diameter] Compatible Model: SAPR402G, fit for most brands of PA/DJ Subwoofer Bass Speaker Cabinets Box Vent,
Cabinet Cutout: 3" [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] 3" x 3" Speaker Port Tubes - 2Pack