If this helps, using a Fuji JPII C90 in my oldest Tascam 244 recording at 0dB on VU meter Track 1 with dbx I measured the following on replay (other tracks pretty much the same):
25 Hz      -3dB
40 Hz       0dB
100Hz      0dB
400Hz      0dB
1000Hz   -1dB
10000Hz   2dB
12500Hz   2dB
16000Hz...