Yes, the SPL meter should be used to set the sub, as well. It sounds like something is wrong if the sub is only getting to 55db.

You want to set the meter to C weighting. It's how responsive the needle is. Set it to A and it jumps all over the place with quick readings. C slows it down so it's easier to read.

You might go through all the settings on the sub and in the receiver to see where the problem is.

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose