The receivers always start to rolloff the frequencies a little above the crossover frequency. You usually lose 12 dB per octave so a crossover set at 80 Hz would be down 12dB by 40 Hz. With JRSS, at 40 Hz you are still receiving the full signal in your mains.
This is be related to how you have your system calibrated. You might have the gain on the subwoofer turned up too high and your receiver is compensating by lowering the level on that channel (if you have Audyssey or some other room correction in your receiver). You could lower the gain on the sub so that the redirected bass is at the same level as when you just play in stereo. You could also just use the Room Correction DSP in MC to lower the volume level of the sub channel. Then you would probably need to increase the gain in the receiver for that channel. The main point to consider is that currently your subwoofer is playing too loud in relation to your mains when using MC.
I was trying to clarify that if you use the receiver for bass management, you also must use it to upmix. This is because if you upmix to 5.1 in MC and even with the crossover set to None, the full range signal is still sent to the subwoofer. This prevents you from doing any bass management with the receiver. Does this make sense?
Hello, sorry for the extremly late reply, i have been busy getting married.
To clarify, the problemm isn't simply one of the sub gain beeing wrong, the problem is that the relative level of the usb is different in MC in upmixing mode than in stereo-mode, if its perfectly calibrated in stereo, the sub will be to high in upmixing, or the other way around, if i lower the gain, it will be to low in stereo, this is the case no matter what is actually setting the gain (the sub itself, audessey and so on)
I can't see how setting no crossover prevents the receiver from doing managment? First of all, the LFE-track is only up to 120 Hz(?), so MC should only send up to 120 Hz on that track. Secondly, if the receiver has the crossover at for instance 80 Hz, it will only send info that are from 80 Hz and below from the LFE-track, even though it has inof up to 120 Hz, shouldn't this be the case also when MC outputs the 5.1-signal?