No, I'm not sure where that gets me, why I'm asking you. Doesn't answer the question in the way I was thinking at least. AVRs aren't all the same I don't think, have seen some mentions of those with adjustable slopes but rare indeed. Why not just seal the ported speakers when working out a good crossover with them and subs? Why would that not work with the assumption of most avr slopes? Explain this for the OP, not me.
No, I'm not sure where that gets me, why I'm asking you. Doesn't answer the question in the way I was thinking at least. AVRs aren't all the same I don't think, have seen some mentions of those with adjustable slopes but rare indeed. Why not just seal the ported speakers when working out a good crossover with them and subs? Why would that not work with the assumption of most avr slopes? Explain this for the OP, not me.
You may be right that there are AVRs with adjustable slopes, but I have never heard of one. As far as I know AVRs all follow the THX spec of 12 db high pass and 24 db low pass. If you know one that is different I would be very interested. I'm not saying there isn't but I don't know of it.
As I explained sealing the port of a ported speaker is not the answer. For one thing the driver is probably optimized for a ported design. If it is bookshelf then the F3 has a good chance of ending up too high. More importantly the optimal box for a driver sealed is universally smaller than the optimal ported box. If the box is too large, then Q rises and that means boomy.
In fact getting really accurate well defined bass is one of the most difficult challenges in audio. I have wrestled with it for over 60 years now. For classical music it is crucial. For music of the baroque a well defined damped bass is essential, or it sounds laughable and elephantine. For the symphony orchestra having articulate but powerful bass on the lower strings, makes it sound like live. For Wagner, in particular, the hypnotic bass line must be reproduced accurately. Realistic piano reproduction sounds simply awful with an inaccurate resonant bass. For organ music, and especially Bach, the pedal line must articulate clearly with real definition.
I think the issues discussed are why a lot, if not the vast majority of classical music listeners forsake subs and bass management as it is currently conceived.
Pop and rock largely have a synthetic contrived bass before you start, so the issues are different.