For me I think its equality in signals or a memory setting in the receivers.
Let me explain what I've found.
Radio broadcasts seem to have more of a full range of frequency versus CD input, CD player itself. With this placement isnt critical as much since it blends so much better. I can set for small speakers and its really a continuation of the frequency the mains are'nt set to play. I can go large, the same thing, Dolby, Stereo, Full Stereo, it doesnt matter, it blends well.
Running CD's which through either my CD player or my DVD player, it just it seems to have a gap no matter how I set everything up, so mostly during those times I dont run the sub at all and set to large. It seems to have to much distinction between bass management and the other frequencies the speakers get. If I run the sub I end up setting the crossover much higher, all most peak and turning the sub down to get a decent blend, but not as good as radio.
DVD watching is like radio, but I think its how it makes a scene impact better.
For me its all most impossible to get a good blend for all formats and wish something along the lines of a memory setting that locks in the setting , per format so I didnt have to fiddle all the time. Even better would be a format adopted by all formats so this difference didnt exist!!!