I just installed a skar audio rp1200.1 amp and a skar svr 12 in a ported box. The sub has an rms of 800 watts at 1 ohm and the amp 1200 rms at 1 ohm. With my head units volume at 90% using a 40 hz test tone Spotify, I am having trouble getting the required voltage of 28.28 according to the...