True ultra low frequencies below 30Hz take a lot more sound pressure to be heard and to damage your ears but the sub and speakers are going to produce a lot of low-mid and mid bass also.
The hair cells in your ear do not have the capacity to heal themselves. 80dB or higher over prolonged periods will cause hearing damage. So even though each time you watch a movie you only loose 1/10,000 of your hearing capacity, do it enough times over your life span you'll be hard of hearing.
http://www.nidcd.nih.gov/health/hearing/noise.asp
Who knows though with medical technology they might be able to grow you a new ear or use nanotechnology to repair it in the future.