I think you do not understand what is Rembrandt lighting... Rembrandt means 45/45 lighting... you can get it even with 1 light.
It is NOT placed 90 deg to the subject. It is NOT having 2 softboxes with the weaker one in front. The Key light of Rembrandt lighting, is placed 45 deg from the front, at a high angle pointing 45 deg downwards at the subject. That is why it is called 45/45 lighting also.
Please get your lighting basics right before you jump out and tell others how to do it.
Rembrandt lighting - Wikipedia, the free encyclopedia
And BTW, Rembrandt lighting has absolutely nothing to do with separation from the background. Rembrandt lighting is more about the Key light only. Only hair lights, kickers and background lights are used to get separation.