Shawarma, the wavelengths are too long to be affected by your ceiling in any meaningful way. At higher frequencies yes but, not in the bass. If you use a digital preamp like The DEQX Premate, the MiniDSP , The Anthem SLR or the Trinnov Amethyst you can correct this at the listening position nicely but there will still be areas in the room that will be out. Play a bass heavy song and walk around your room. You will hear the character of the bass change as you move around. If you move the measurement mic just a few feet you will get an entirely different frequency response curve. It is just the nature of the beast. Some rooms are better than others. Bass is particularly difficult and all the room treatment in the world will not change that. Room treatments are very useful at higher frequencies. Best is to use speakers with controlled limited dispersion but still bass will be a problem. This can be fixed at the listening position with DSP at the expense of amplifier power and worse response at other places in the room.
What are ways to fix speaker dips in my speaker or audio room
I have recently hired an acoustic engineer and after a day of measuring room acoustics and he came back with what I needed to fix and one of my speakers dip at 54 HZ and would DSP help or a lot of bass traps in the frequency work better?