WIthout a schematic its hard to say, but I wouldnt think so…having missing low end…seems like an issue like this could be many things.
If the bass is there but at a reduced sound level…maybe the amp on the one channel?
Crossover in a speaker possible.
Tone control in the amp?
Try different speakers on both channels?
Put an O-scope on the output and play test tones or freq generator sweep on amps outputs…to see for sure…