This is weird.

[mlstrass 5,000+ posts]

Can anybody vouch for the validity of this?

Sit in a car that does mid 50's @ 30Hz, it'll move a TON of air, but not really hit your body or ears. Sit in a car that does mid 50's @ 45Hz and your ears will hurt and you'll probably feel it in the throat...

 

[mlstrass 5,000+ posts]

...

 

[mazdakid 5,000+ posts]

Lower to a point usually sounds louder to the ear, and higher "usually" meters better. Depends upon vehicle, sub, tuning, power, ect...
I also wouldn't expect a single SA 15 to be painful

But its sundown.

 

[mlstrass 5,000+ posts]

But its sundown.

My bad, didn't realize that and I know nothing about being loud so I'll shut up now...