I always thought my sub was pretty flat in my room, was I ever fricken surprised. I down loaded some test tones and I started making some measurements with my digital rad shack sound pressure meter. I did not use my reference volume because the test tones were just to dam loud, I picked a volume I could stand and was consistent throughout. My tests consisted of 18 hz to 85 hz. If I had a BFD, could it help me and where would I start. Here are my results.

18hz-77db
19hz-79db
20hz-83db
21hz-83db
22-83
23-91
24-94
25-95
26-95
27-95
28-95
29-94
30-94
32-94
33-93
34-92
35-91
36-90
37-89
38-89
39-90
40-91
41-93
42-94
43-95
44-97
45-97
46-98
47-97
48-96
49-95
50-94
51-92
52-90
53-88
54-86
55-82
56-79
57-73
58-71
59-72
60hz-78db
61-81
62-83
63-85
64-87
65-87
66-87
67-87
68-86
69-85
70-84
71-81
72-76
73-76
74-80
75-84
76-86
77-87
78-88
79-90
80-91
81-92
82-92
83-93
84-94
85-94
I start getting some good output starting at about 23 hz but look at 58hz, it just dies. And look at 72hz, It's 1 db lower then at 18 hz which to tell you the truth, when I started at 18 hz I could barely hear anything, if it wasn't for my meter I would have swore my 18 hz test tone wasn't even playing. Between 23hz and 80 hz I could be as low as 71 db and as high as 98db at 46 hz. That is a 27 db difference with alot more differences in the 15 db range. If these were your measurements, what would you do and where would you start.