I found this link to SVS that shows how to compensate for the bass rolloff in Radio Shack meters. While it doesn't deal with your general problem, it might help your tuning.

http://www.svsubwoofers.com/faq_rscomp.htm
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Living Room 24x18 open 1/2 flight up to a raised dining room/hall 24x12
Outlaw 976 pre-pro running 5.1 system
Outlaw 750 for Artison Masterpiece LCR and 2 NHT SuperZeros rears
Velodyne Servo FX-1200
LG OLED65C8PUA via HDMI2 to/from 976 HDMI ARC
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