An octave is 10 Hz then 20 Hz, then 40 and so on. There is a formula for room gain: C/2*L, C is the speed of sound and L is the length of the room.
Example: 1130/2* 20 ft. =28.5 Hz so you will start gain 12 db/octave starting at 28.5.. This mean at 14Hz you will be up 12 db. Room gain is not boundary gain which is usually 2-5 db.
Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus 200 Five, Dayton 18 Ultimxa Dual Sub Cab(2), Dayton 18 Ultimax Large Vented Sub Cab (2), on Berhinger I Nuke DPS amps, Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500