2015 stock HU rear speaker output question

Does anyone know if the rear channel is filtered or is full output?

I have 6x9’s running off an amp that is driven only by the front channels. So I decided to install some aftermarket tweeters in the stock tweet location and run them off the rear channel, in that they would be better than the headliner speakers. i went with Alpine type s tweeters. I installed them with the supplied crossover but the sound was pretty weak and so I removed the crossovers and it sounds better, no low end but some decent mids which has me worried about blowing. It’s not that loud though, so I think maybe the HU is filtering the output to the rear because the headliners were so awful. Does anyone know what the output of the rear channels is?