I just bought my 25-31PC+ from a friend (you know who you are Thank you ) and I think I know how to tune it to 20Hz? You pry the grill off, then put in one port blocker and set the dial to 20 instead of 25 right ! now the real question! is there a lot of content that I am missing leaving it at 25Hz? The reason I ask is sometimes I see LFE activety and I don't feel or hear anything! Also how far in do you put the blocker and how do you get it back out once its in there? Thanks for your help!! I will give a small review once I put the unit threw all the motions!! So far I love this thing!