Boxes · In every box
MODELQL · QA · QPLosses and damping
The three losses#
Each loss is a Q value: the higher the Q, the smaller the loss. Leakage and absorption are set against the chamber’s own tuning, so the same Q damps a small box as much as a big one.
| Loss | Q | Where | What it stands for |
|---|---|---|---|
| Leakage, Ql | 10 | Every chamber: sealed, vented, passive radiator and both bandpass chambers | Air escaping through joints, gaskets and the driver. It is set against the chamber’s tuning; in a sealed box, against its resonance with the driver. |
| Absorption, Qa | 100 | Chambers with a port | Damping of the air inside the chamber as it is squeezed and let go. |
| Port loss, Qp | 100 | Ports with the Lumped port model | Friction in the port. A port with the Distributed model uses its Duct loss instead: see Ports and end correction. |
- There is no control for them in the enclosure panel, and the 00 Simulator connector cannot change them for boxes either.
- Air that leaks from a sealed or vented box is added to what the box radiates. A passive radiator box leaves it out.
- Boxes have no stuffing or lining setting: damping material in a box is not modelled beyond these fixed losses.
How much they matter#
Leakage matters most, and most near the tuning, where the port does the work. To show it, the figures run the vented example through the same solver with a leakier and a tighter box. You cannot set these in the app; they show how far a real box could sit from the model.
SPL
dB
- Ql 5, leakierF3 33.5 Hz · At 32 Hz 104.2 dB
- Ql 10, as the app models itF3 30.3 Hz · At 32 Hz 106.1 dB
- Ql 20, tighterF3 29.4 Hz · At 32 Hz 107.3 dB
From Ql 5 to Ql 20 the level at 32 Hz rises from 104.2 dB to 107.3 dB, and F3 falls from 33.5 Hz to 29.4 Hz. The air in the port speeds up with it: 16.2 to 22.8 m/s at 100 W. With next to no losses at all (every Q at 1,000) the example would play 3.0 dB louder at the tuning; the leakage alone accounts for 2.5 dB of that.
Impedance
Ω
- Ql 5, leakierPeaks 20.3 Ω and 18.2 Ω · Dip 5.6 Ω at 31.6 Hz
- Ql 10, as the app models itPeaks 22.8 Ω and 21.0 Ω · Dip 4.6 Ω at 31.6 Hz
- Ql 20, tighterPeaks 24.4 Ω and 22.8 Ω · Dip 4.1 Ω at 31.6 Hz
Impedance shows losses most clearly. A vented box has two peaks either side of the tuning and a dip between them; the leakier the box, the lower the peaks and the shallower the dip. The example’s peaks are 22.8 Ω and 21.0 Ω.
A sealed box feels its leak too. Without it, the sealed example’s F3 at 50 W would fall from 62.2 Hz to 59.7 Hz, and its impedance peak would rise from 40.4 Ω to 63.7 Ω.
Check it against your box#
Measure the impedance of the box you built and import it as a measured trace: it draws over the Impedance tile beside the simulation. Peaks taller than the simulated ones point to a tighter box than Ql 10, lower ones to a leakier box or more damping. Expect the response near the tuning to differ the same way.
Horns and the air#
- Horns work differently: their paths can be stuffed segment by segment. See Stuffing.
- The air in every design is at 20 °C: sound travels at 343 m/s and its density is 1.201 kg/m³.
Ask your AI#
Ask your AI
Using 00 Simulator, compare the measured impedance trace in my open workspace with the enclosure it belongs to, and tell me where the measured peaks and the dip between them differ from the simulation.
Connect your assistant so it can open your designs.