Add onto previous thread about transmission line speakers.

Hello everyone its Bazza.
So an add on to previous thread, about the bass. Iv done a low frequency test from 25hz to 150hz amd this is what I got. Up to 49hz nothing 50hz it begins up to 80hz. From 75hz to 120hz ish flattens out onwards to 150hz.
What I don't get is this, songs that I know produce the hi pressure in the gut type bass I should get..I don't! I get instead a vibration a heavy type. .
50-70hz is nice. I don't understand?