ultrasonic volume of older subs question

[maxx55]

I believe the volumes are different! I have AoS and BIATBWS, they both have Trickling Stream tracks (obviously), but they are different sounding. And one IS louder than the other, the AoS is the quieter and I believe it's older. EPRHA and BIATBWS had the same sounding trickling stream track so I assume both are newer. So you have calibrate the ultrasonic to it's respective masked track to accurately measure the volume.