You would lose the frequencies below 80Hz if you set your front speakers to "small" in your receivers speaker menu, and if the crossover is fixed at 80Hz, or you manually set it to 80Hz. And actually, the crossover is not a brick wall. It's not like everything below 80Hz is gone.
80Hz is where the volume STARTS to drop off. How much below the 80Hz is audible is a factor of the crossover
slope. As you can see, with a 6dB per octave slope, anything available at 40Hz (1 octave lower than 80Hz) would be 6dB quieter than anything at 80 Hz. (Have I got that correct guys?)
However, if you don't have a sub, and you set your front speakers to "large" in your receiver's menu, they will reproduce the entire frequency spectrum they are capable of reproducing. You would only set your main speakers to "small" if have a sub.
