A couple of years ago, I bought a house that had a theater room in the basement. The previous owner left the rear speakers installed in the wall. I pulled one out and learned they are Tannoy iw60 efx boxes. I found the manual online. I'm a speaker noob. I read the cinema mode is 4 ohms while a music mode is 8 ohms. My receiver only goes down to 6 ohms. So, I assume I need the speakers to be in music mode. I have no clue how to do this. I would appreciate any help. Also, advice on whether these will be good rear surround speakers would be great. Thanks!