Does min distance from diffuser apply to source of sound also?

I understand than when listening to playback there is a specified minimum distance that should be kept between the diffusion device and the listening position with that distance dictated by the design of the device. But what about the distance between the source of the sound and a diffusion device? For instance, if I want to set up some mobile QRD's behind a drum set or acoustic guitar does the minimum distance for the diffuser design apply to that scenario, as well? Or what about an array of diffusers on the wall behind dipole speakers (where the distance from the speaker panel to the tallest point on the diffuser is around 4' and the distance from the listening position to the tallest point on the diffuser is around 14')? If the source of sound is located closer to the device than the minimum distance specified for device/listening position will there be any artifacts in the diffused sound field?

Does min distance from diffuser apply to source of sound also?