Enclosure Losses, Leakage, And Damping
Canonical Definition
Enclosure losses are mechanisms that dissipate, redirect, or time-vary energy in the driver-box-port system. They include air leakage, damping absorption, port resistance, panel and structural radiation, joints, material loss, and model error such as unrepresented suspension creep.
Loss Terms Are Not Interchangeable
| Mechanism | Typical evidence | Physical check |
|---|---|---|
| Air leak | changed pressure, peak shape, or modulated turbulent noise | gaskets, seams, terminal cups, dust cap |
| Absorption | reduced resonance energy and changed apparent compliance | fill type, density, position, port clearance |
| Port loss | level-dependent output reduction, resistance, and tuning shift | area, geometry, flow, boundaries |
| Panel radiation | cabinet vibration and extra acoustic output | bracing, joints, panel scan or accelerometer |
| Driver model limits | fit error that changes with frequency, level, or time | creep, temperature, nonlinear parameters |
Ql Is A Model Parameter, Not A Leak Detector
A single enclosure-loss quality factor can help fit a simple model, but it does not prove that literal air leakage is the cause. More complete models can separate leakage, absorption, port resistance, and viscoelastic driver behavior. Always return from the mathematical fit to a physical inspection.
Why Impedance Alone Can Miss A Defect
A small leak may generate audible turbulent noise while barely changing the low-level input impedance. Combine impedance with near-field response, leak-noise or random-distortion analysis, panel checks, and one controlled physical change at a time.
Verification Sequence
- Capture a cool, low-level impedance and acoustic baseline.
- Inspect and document seams, gaskets, terminals, ports, fill, braces, and panels.
- Measure leak or turbulent noise at a repeatable low-frequency stimulus.
- Raise level to expose port or panel nonlinearity.
- Change one physical mechanism and repeat the same tests.