Solution for Bass Rumble?

Solution for bass rumble?

Hello, I am a newcomer and need advice from you. I bought Klipsch the Fives for my new apartment. As soon as I set it up and played music I noticed really disturbing bass rumble when I sit on the couch, especially in the corner. It even happens when a truck passes by the building. It’s definitely caused by the shape of the room. I am thinking about lowering the bass of the speakers through the Klipsch app and add a subwoofer to the opposite corner of the room to still be able to have sufficient amount of bass. I draw a simple diagram of the room. Please tell me if this is a stupid solution and I am open for your completely different advices.