Look at the graphics equalizer settings to see if you have selected large hall, large room or any other setting that is available. Then turn that setting off.
If you are talking about the driver cones in each of the units, then it's odd that they should have gone, unless they have driven too hard or damaged (say by a child poking them). Double unit speakers have a crossover built into that separates the sound into treble and midrange or bass.
If the sound coming out is "treble" the high frequency that shows the bass units are not working.
Make certain all the wiring is good to the speakers and if you can see the bass speaker check it is not damaged.
If you need to, go inside the units and connect a 1.5 battery across each speaker terminal for a second. If it "pops" then it's working.
