it's the same for me; i calibrate my sound system and the results
give me weak output from the sub; maybe it's flat frequency response, but it's too weak.
the first time i increased the gain on the sub, i discovered some very low frequencies in the music that i have not heard before.
i discovered also that tv programs often do have those lows too.
then, i decided to do it by ear on easy to judge scenes in some movies, like the ring drop in LOTR.
when those few seconds are played over and over while adjusting the sub vol. control, one soon sees/hears, according to the distance and the sound qualities, what the right sub volume should be.
for me i had to increase the sub's output in the receiver by 3dB.
since then i've read from a lot of other people that they find the +3dB increase is the right one to use. it gives to the ears a flat freq. resp.
