How harmful is it to play regular music on a bass subwoofer?

[BB]

I hooked up my MTX jackhammers to my friends amplifier in his car, a 900 watt sony mono amp. He pressed play and all I heard was the music and not bass from the song since the song had no bass in the beginning. So after no more than 10 seconds, I said shut it off and disconnected my subs from his car. I connected my subs back to my car and it sounded fine. I was just wondering if it harmed the sub or could have harmed the sub.

Thanks