53 T/S Drivers 108 Blueprints

Subwoofer Port Length & Helmholtz Tuning Calculator

Calculate exact bass-reflex port length (Lv), reverse tuning frequency (Fb), minimum port diameter, and peak port air velocity for cylindrical PVC pipes and rectangular slot ports.

Port Length Lv
94.2 mm
9.42 cm / 3.71 in
Reverse Tuning Fb
62 Hz
Peak Air Velocity
8.4 m/s
Total Port Area Sp
13.2 cm²
1/2-Wave Pipe Resonance
1415 Hz
Min Laminar Ø
Ø 1.7 mm

JIS K 6741 VP / VU & US Schedule 40 PVC Pipe Standards

Standard Specification Inner / Outer Ø Ref Length at 8.5L / 62Hz
VP20 — JIS VP JIS VP20 — Ø 20.0 mm ID 20 mm / OD 26 mm 15.7 mm
VP25 — JIS VP JIS VP25 — Ø 25.0 mm ID 25 mm / OD 32 mm 28.6 mm
VP30 — JIS VP JIS VP30 — Ø 31.0 mm ID 31 mm / OD 38 mm 48.9 mm
VP40 — JIS VP JIS VP40 — Ø 41.0 mm ID 41 mm / OD 48 mm 94.2 mm
VP50 — JIS VP JIS VP50 — Ø 51.0 mm ID 51 mm / OD 60 mm 154 mm
VP65 — JIS VP JIS VP65 — Ø 67.0 mm ID 67 mm / OD 76 mm 279.6 mm
VP75 — JIS VP JIS VP75 — Ø 77.0 mm ID 77 mm / OD 89 mm 376.8 mm
VP100 — JIS VP JIS VP100 — Ø 100.0 mm ID 100 mm / OD 114 mm 655.2 mm
VU40 — JIS VU JIS VU40 — Ø 44.0 mm ID 44 mm / OD 48 mm 110.6 mm
VU50 — JIS VU JIS VU50 — Ø 56.0 mm ID 56 mm / OD 60 mm 189.2 mm
VU65 — JIS VU JIS VU65 — Ø 71.0 mm ID 71 mm / OD 76 mm 316.7 mm
VU75 — JIS VU JIS VU75 — Ø 83.0 mm ID 83 mm / OD 89 mm 442.1 mm
VU100 — JIS VU JIS VU100 — Ø 107.0 mm ID 107 mm / OD 114 mm 755.1 mm
1.5" Sch40 — US Sch40 US 1.5" Schedule 40 — Ø 40.9 mm ID 40.9 mm / OD 48.3 mm 93.7 mm
2" Sch40 — US Sch40 US 2.0" Schedule 40 — Ø 52.5 mm ID 52.5 mm / OD 60.3 mm 164.2 mm
3" Sch40 — US Sch40 US 3.0" Schedule 40 — Ø 77.9 mm ID 77.9 mm / OD 88.9 mm 386.3 mm
4" Sch40 — US Sch40 US 4.0" Schedule 40 — Ø 102.3 mm ID 102.3 mm / OD 114.3 mm 687.3 mm
6" Sch40 — US Sch40 US 6.0" Schedule 40 — Ø 154.1 mm ID 154.1 mm / OD 168.3 mm 1610.9 mm