Looks like you are lighting the bg separately from the subject. The tonal difference between subject and bg can be controlled separately. Looks like you have plenty of distance to the bg, 8-10 feet? If you slide the subject and lights closer to the bg should be able to pick up some more brightness there from your bg light based on inverse square rule. I saw your other post with this shot in it. The bg is pretty narrow for more than one or two of people so I don't expect it to be a group shot. I don't expect this is a full length shot with no sweep and the bg/floor arrangement, so you could avoid the hazard of dropping a light on someone's head, having to work with a cumbersome boom and not have to climb a ladder or pull down the light to adjust if you don't have wireless controls if you mounted a stud to a board an placed the light right behind the subject or used a bg stand as another poster showed. Easily accessible, for power and aiming. You don't need a soft box, a light reflector is all needed and if I want to create a fall off, just pop in a grid. As to the tone of the bg, it is dependent on the difference from the exposure on the subject and bg. Decrease the power of the light on the subject, re set the camera exposure and the bg will be relatively brighter if you leave it the same. I use a reflective meter reading of the bg from my stool, and adjust it to the desired difference to incident reading of subject and get exactly the shade I want instantly. No fumbling around shooting, chimping shooting chimping endlessly, not very professional or efficient. Messing around like that can lose the connection with the subject and the mood. I can take spot reflective readings all around the subject to check they are pretty even. If the incident reading and bg reading are the same, the bg will have it's actual tone.