yep, that matches the measurements I did a little after buying it, heres the wholes song average.
As far as *musical* bass is concerned, I find there is very little content under 30 hz in electronic music tracks (that sell over 100 copies). There will surely be the tail end of sweeps that extend down into the mid to low 20s, but as far as actual components of the bassline, thats where people usually draw the line, esp in in deep bass music like this, because the whole idea is to be immersed in bass, not imagining where the bass would be if those 12 dual 18s in front of you could actually play the notes
Its actually probably not a good idea for you to blast your tune on the AE tdh18 in 8 cubic feet, as the heat of the bassline will be around tuning... meaning the cone will be moving verrry little, so even with its 2 to 3 times heat dissapating action... you might still turn this track into a woofercooker.
We're still wondering what type of music you actually listen to though OP! most of the designs have been sacrificing efficiency and output to get you a solid 30hz, because this is the floor for music, and the wheelhouse for HT.