The small sub may not keep up with the larger one. Set the large one further away and integrate it with the mains. Then level match the smaller one in a nearfield location to match the larger one with an spl meter. Eventually sell the small one and get another 12 in sub.
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, Aura Bass shakers, Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500