Bitrate, whether transmitted digitally or with analog radio, should only affect the upper frequencies. This is because you need to sample an audio wave at a rate of at least twice that of the wave itself. To capture a 20kHz signal, you need a sample frequency of at least 40 kHz. Therefore, to sample 40 Hz, you only need a sample frequency of 80 Hz.
Any bass you're missing is probably due to the equipment that recorded or is processing that signal, at the transmitter end.
Don't quote me on this, but I think terrestrial TV is encoded with FM modulation, for a frequency range of 20 to 20 kHz. It may have a maximum of 15kHz though, I need to check my textbooks.