Cookbook · Sealed
Can an 8-inch driver make useful 40 Hz bass in 15 litres?
This example starts with a Dayton Audio DCS205-4 in a 15 litre sealed box. Change the driver or power below and watch both graphs: SPL shows what the box produces; excursion shows when the driver starts to run out of travel.
Why sealed here?
A sealed box removes port tuning and duct geometry from the first experiment. That leaves a clean driver-and-volume problem: how much low-frequency output is available, and what does it cost in cone travel?
We keep the box at 15 L while you swap drivers. That is useful for comparison, but it is not a recommendation that every driver on the list belongs in a 15 L cabinet.
Interactive example
Try the 15 litre box
Change one input and watch both graphs. These curves are recalculated in your browser by the same simulation engine as the main app.
- Fs
- 32.3 Hz
- Qts
- 0.37
- Vas
- 27.0 L
- Xmax
- 8.8 mm
- Pe
- 150 W
About 14.0 V RMS from Re. Actual current and delivered power change with impedance.
- F3
- 67.0 Hz
- SPL at 40 Hz
- 94.5 dB
- Peak shown
- 7.9 / 8.8 mm
- System Qtc
- 0.62
Response shape
Half-space, 1 m
Excursion / Xmax
Fsc 54.0 Hz
The graph stays below Xmax, but the solver continues down to 5 Hz and reaches 9.9 mm at 5 Hz. If the source contains energy that low, use a suitable high-pass filter or less drive.
SPL response
Power moves the curve up; the driver and box set its shape. Hover or click to read a point.
Cone excursion
Read this beside SPL. The dashed line marks the selected driver's library Xmax.
Continue with this driver and power setting. The simulator will load the same 15 L sealed enclosure so you can add filters, compare alignments and save the design.
Three things to try
Move from 1 W to 10 W
The SPL curve rises by about 10 dB, but F3 and Qtc stay put. In this linear model, power buys level; it does not change the alignment or add extension.
Compare 50 W with 100 W
Excursion grows with the square root of power, so doubling the setting adds about 41% more travel. Watch where the excursion curve meets the selected driver's library Xmax. The solver also runs below the graph's 10 Hz edge, because subsonic content still moves the cone.
Swap the driver
The box has not changed, but the response shape, system Q and excursion all do. That is the useful comparison: the alignment belongs to the driver and enclosure together, not to either one on its own.
Before you cut wood
- Use net air volume. Subtract the driver, bracing, amplifier and anything else inside the cabinet.
- Check the driver data. Fs, Qts, Vas, Re and Sd are model inputs; Xmax is a separate manufacturer limit, not a T/S parameter.
- Translate the power setting into amplifier voltage. The model derives drive voltage from Re; real current and delivered power follow the changing impedance curve.
- Decide the lowest frequency the system must reproduce. If content extends lower, include the intended high-pass filter in the final design.
After the build
- Measure the finished impedance curve. A shifted resonance or an odd peak shape can point to the wrong net volume, a leak or different driver parameters.
- Measure the acoustic response before adding room correction, and write down the microphone position and test conditions.
- Raise the level gradually while listening for mechanical noise and watching amplifier clipping and distortion. Xmax is not a promise of clean output.