winkychevelle 10+ year member
CarAudio.com Veteran
I must be confused what cabin gain is. Back to school for me. Where would my box peak outside of my truck?
Outside your truck pointing in a direction with no immediate reflections and measured 1-3ft away you box should peak at tuning. Then running the same volume on the radio same amp same frequency sweep test track and same meter distance in the truck, the difference between the two should be the gain.
This is easiest to measure with a sealed box since the graphs are generally smoother.
Smaller vehicles usually gain at lower frequency larger vehicles gain at higher frequency. That super tight kick in the chest bass is often caused by cabin gain where as most vehicles have a null in the same frequency range.