25hz bass but none at 30

[admin_exported]

bit odd but with my main speakers i get no response at 30 hz but at 25hz the bass was quite strong. (sub was off) anyone able to shed any light on why this may be. When pushed bass is very strong to 65hz and strong down to 45hz.

 

[MattSPL]

Rooms suffer from uneven frequency response.
The size and shape of your room will determine certain frequencies that suffer both from suck outs, and boosts in bass performance.

If you google 'Room mode calculator', you should be able to calculate your rooms problem frequencies.

Sub position could help greatly with your problem, and adding a second sub would be even better.