Choosing a soundbar for an off-road vehicle requires more than reading a peak-wattage label. RMS output shows the power a speaker can sustain during a controlled test. It is more useful than a brief marketing peak. IEC 60268-5 provides a framework for loudspeaker measurements, including rated power, sensitivity, and frequency response. A reliable comparison should use the same signal, mounting position, impedance, and measurement distance. Small setup changes can alter the result.
THD, or total harmonic distortion, shows how much unwanted harmonic content appears beside the original signal. Lower THD usually means cleaner vocals, especially when the system plays loudly. Measure it at several RMS levels, not only at a comfortable volume. A soundbar may stay clean at moderate output, then become harsh near its limit. Listen for buzzing around the enclosure. It matters.
In a practical vehicle test, I would record RMS output at one meter and note the tested frequency range. I would also log THD at low, medium, and high levels. These details reveal more than one impressive number. However, IEC-style laboratory results do not perfectly predict performance inside a cabin. Wind, engine noise, reflective panels, and uneven mounting can change what the listener hears. My own measurements would need repeated trials, because one reading can be misleading. A better model may measure well but sound less convincing from the driver’s seat.