Just to clarify. If you have a bass bump below 150 Hz, it's very difficult (not impossible) to treat it with physical devices. There are really only 2 physical devices for this: absorbers and resonators. An abosber that is efficient at that frequency (say 100 Hz for example) is only as efficient as the area of the space that is accentuating the frequency. So, if 2 parrallel walls are accentuating the frequency and you have an absorver that is 95% efficient at that frequency, but you only cover 5% of the wall space--then you've only made a 4.5% difference on the problem (not even audible). This is why people wonder, when they buy bass traps that are proported as being 90% or greater efficient at their frequency problem--why don't they hear a difference (or very much of one). The other way of dealing with problem is resonators. Yes, these can go to just about any frequency and almost any Q factor. The only problem is expense and size of their construction. They also have to be placed at very critical points in the room, where the peaks are maximized (not the pressure points like an absorber). In addition they re-radiate energy--so the design is critical in that the re-radiated energy doesn't cause more problems than the resonator solves. And yes, it's just under 2.5 octaves, but you can't use the piano as an ear test for this because so much of the energy is higher ordered harmonics. To test this theory you have to use pure tone generators don't have (other than what the room produces) harmonics.
