As no one has posted these for a while and there may be new members here playing with new subs and/or anyone dipping their toes into room acoustics, here are some correction values for the Tandy (Radio Shack) spl meter (both the analogue and digital versions as they use the same "engine") to be applied due to mic inefficiencies.
The left column represents a/the test tone frequency
the right column represents the value to be added to the recorded value of the frequency of the left column.
16hz Add (+) 11.5db
18hz Add (+) 8.0db
20hz Add (+) 7.5db
22hz Add (+) 6.5db
25hz Add (+) 5.0db
28hz Add (+) 4.0db
31.5hz Add (+) 3.0db
36hz Add (+) 2.5db
40hz Add (+) 2.5db
45hz Add (+) 2.0db
50hz Add (+) 1.5db
56hz Add (+) 1.5db
63hz Add (+) 1.5db
71hz Add (+) 2.5db
80hz Add (+) 1.5db
89hz Add (+) 1.5db
Steve.
The left column represents a/the test tone frequency
the right column represents the value to be added to the recorded value of the frequency of the left column.
16hz Add (+) 11.5db
18hz Add (+) 8.0db
20hz Add (+) 7.5db
22hz Add (+) 6.5db
25hz Add (+) 5.0db
28hz Add (+) 4.0db
31.5hz Add (+) 3.0db
36hz Add (+) 2.5db
40hz Add (+) 2.5db
45hz Add (+) 2.0db
50hz Add (+) 1.5db
56hz Add (+) 1.5db
63hz Add (+) 1.5db
71hz Add (+) 2.5db
80hz Add (+) 1.5db
89hz Add (+) 1.5db
Steve.