Example Data Table
| Box Style | Internal Size | Drivers | Gross Volume | Displacement | Estimated Net Airspace |
|---|---|---|---|---|---|
| Sealed Rectangular | 30 × 14 × 16 in | 1 | 3.89 cu ft | 0.08 cu ft | 3.81 cu ft |
| Ported Rectangular | 32 × 15 × 18 in | 2 | 5.00 cu ft | 0.42 cu ft | 4.58 cu ft |
| Wedge Truck Box | 28 × avg 13 × avg 11 in | 1 | 2.32 cu ft | 0.10 cu ft | 2.22 cu ft |
Formula Used
Rectangular gross volume equals width multiplied by height and depth. Wedge gross volume uses average depth and average height. Cylindrical volume uses π × radius² × length. External dimensions are reduced by two material thicknesses.
Net airspace equals gross volume minus driver displacement, port displacement, bracing displacement, and other internal displacement. Per driver airspace equals net airspace divided by driver count.
Round port area equals π × radius². Slot port area equals width × height. Port displacement equals port area × port length × port count. Tuning is estimated with a simplified Helmholtz relation.
How To Use This Calculator
- Select the enclosure shape and box type.
- Choose internal dimensions or external dimensions.
- Enter width, height, depth, or cylinder measurements.
- Add material thickness when using outside measurements.
- Enter driver count and displacement values.
- Add port details for a vented enclosure.
- Enter target airspace per driver when available.
- Press calculate and review the result above the form.
Speaker Box Airspace Guide
Why Airspace Matters
Speaker box airspace controls how a driver loads, moves, and sounds. Too little airspace can raise system stiffness. The bass may become tight, but output can suffer. Too much airspace can reduce control. It may also increase cone travel near low notes. A good enclosure uses the driver maker’s target volume. It then adjusts that value for real construction parts.
Gross Volume And Net Volume
Gross volume is the empty internal space of the cabinet. Net volume is the useful space after internal parts are removed. Drivers, ports, bracing, terminals, and blocks occupy space. Their volume should not be ignored. This calculator subtracts those values from the gross box space. The result is the working air chamber seen by the speaker.
Sealed And Ported Planning
A sealed box is simpler. It only needs driver and hardware displacement removed. A ported box needs more care. The port body occupies airspace inside the cabinet. Its area and length also affect tuning. A longer port often lowers tuning. A larger port area can reduce noise. It may also need more length.
Shape Choices
Rectangular boxes suit most builds. Wedge boxes fit trucks and angled spaces. Cylindrical boxes help with tube style enclosures. Each shape uses a different gross volume method. For wedge boxes, average depth and height give a practical estimate. For final cutting, measure every panel carefully.
Build Notes
Always confirm the driver’s recommended sealed or ported volume. Use internal measurements when possible. If only outside measurements are known, enter material thickness. Add extra displacement for large braces or double baffles. Compare the target difference before cutting panels. Small errors can change the final response. Careful planning helps the box match the intended bass character.
FAQs
What is speaker box airspace?
It is the internal enclosure volume available for the speaker. Net airspace removes the space taken by drivers, ports, braces, and other internal parts.
What is the difference between gross and net volume?
Gross volume is the empty cabinet space. Net volume is the usable airspace after subtracting all internal displacement from drivers, ports, braces, and hardware.
Should I use internal or external dimensions?
Use internal dimensions when available. If you use external dimensions, enter the material thickness so the calculator can estimate the internal cabinet space.
Does driver displacement matter?
Yes. The speaker basket and magnet sit inside the enclosure. Their displacement reduces usable airspace and can affect the final sound.
Does port displacement count in a ported box?
Yes. The physical port tube or slot occupies internal volume. This calculator subtracts that port body space from the gross enclosure volume.
Can this calculator handle wedge boxes?
Yes. It estimates wedge volume by averaging top and bottom depth, plus front and back height. This gives a practical planning value.
Why is my target difference negative?
A negative value means the calculated net airspace is smaller than your target. You may need a larger box or lower internal displacement.
Is the port tuning exact?
The tuning value is an estimate. Real tuning can change because of port ends, bends, cabin loading, wall effects, and construction details.