Sealed, ported, or passive radiator?
Three ways to build bass. Find the one that fits your driver, your space, and your goals.
5 min read / A practical starting point
Start with your constraints
There is no enclosure type that is best for every driver, available space, and output target. Start with the enclosure that meets your size, response, excursion, and construction constraints. Then build and measure it.
Sealed: mechanical simplicity
A sealed box is mechanically simple. Its trapped air adds stiffness to the driver, so a smaller box raises system resonance and changes damping. There is no vent to create turbulence, but output at low frequencies still requires cone travel and amplifier power.
Use the sealed-box calculator to see the volume, system Q, and cutoff together.
Ported: a resonant air mass
A ported box adds a resonant air mass. Around tuning, the port can provide much of the output while reducing cone movement. Below tuning, that benefit disappears and cone excursion can rise quickly.
A viable design needs more than a target tuning frequency: check the ported-box response, physical port length, and air velocity.
Passive radiator: a different moving mass
A passive radiator substitutes a moving diaphragm for the air mass in a vent. It can be useful when the required port is too long, but it has its own suspension, moving mass, losses, and excursion limit.
Added weight changes tuning; it does not create unlimited displacement capacity. Check both using the passive-radiator calculator.
Make the comparison meaningful
Equal-looking response curves can conceal very different demands on the driver, vent, or radiator. Use the same drive conditions, net volume conventions, and radiation assumptions when comparing a design.
