I just got my second PB13-ultra and I noticed the new one seems to have more output then the original which is only three months old. They are both corner loaded in the back of the living room facing each other. With both gains set at 10 o'clock the new one seemed to have more extension and be pushing more air. measurements with my spl meter confirmed the new one is 2-6 dbs louder. I took the measurements at my usual music listening level. I measured about a foot in front of the driver and the new one was at 120 dbs while the original was at about 114. I took measurements with the BFD filters on and also in bypass and the results were the same. I adjusted the gain on the original up, but by 2 o'clock on the dial it still wasn't caught up to the new one and I didn't want to push it any further. It is it usual for two identical subs to have such different outputs?