How to choose a subwoofer driver for a sealed box
A practical guide to picking a subwoofer driver for a sealed enclosure — what the Thiele-Small parameters mean, what size to get, and how to match a driver to your space and goals.
Picking the right driver is the first decision in any subwoofer build. Here is what actually matters.
Start with the goal and the space
- Music / home theatre, normal room: a 10 or 12 inch driver in a sealed box is the sweet spot — tight, accurate, and a manageable box size.
- Large room or maximum impact: step up to 15 or 18 inch, or use two drivers.
- Car audio: size to the boot space you have; sealed boxes are compact and sound great on the move.
The Thiele-Small parameters that matter
You do not need to be an engineer, but a few numbers tell the story:
- Fs — the driver’s free-air resonance. Lower Fs hints at deeper extension.
- Qts — the total Q. For a sealed box, a moderate Qts (about 0.4 to 0.7) is ideal.
- Vas — the equivalent air compliance. Large Vas usually means a larger box.
- Xmax — how far the cone moves. More Xmax means more clean output.
- Pe — power handling.
The good news: you do not have to crunch these yourself. For every driver we publish a plan for, we have already solved the exact sealed box it wants, tuned to a maximally flat alignment.
How to decide
- Pick a size that fits your space and output goal.
- Choose a driver with solid Xmax and power handling for the loudness you want.
- Check there is a sealed plan for it — then you know the box is right before you cut a single panel.
Browse the plans by size to see which drivers already have a build-ready sealed design.
Frequently asked questions
- What size subwoofer should I get?
- Bigger cones move more air and play louder with less effort, but need bigger boxes. A 10 or 12 inch driver suits most rooms and cars; 15 and 18 inch drivers are for large rooms and high-output builds.
- What is the most important spec for a sealed box?
- Qts together with Vas. A driver with a moderate Qts (roughly 0.4 to 0.7) and a sensible Vas works beautifully in a sealed box. Our plans are solved to the exact box each driver wants.
- Can any subwoofer go in a sealed box?
- Most can. Drivers with a very low Qts are happiest ported, but the vast majority of subwoofer drivers make an excellent sealed box, which is also the most forgiving enclosure to build.