The JL Audio Fathom f113 has a setting called the E.L.F trim (Extreme Low Frequency). It can either boost the low end by 3 dB or cut it down by 12 dB (or anything in-between). The range of the setting is wide and also the corner frequency is high enough so that the subwoofer can be also set up in the very smallest rooms without excessive low end output. The JL Audio has executed this control very well.
The measurement below is showing the extreme ends of the setting (fully variable control).
