Wouldn't the speaker crossover networks determine the slope, whether it be 12, 18, 24, or whatever dB? I have never read this spec for any crossover in a HT receiver.
Yeah, whatever the internal crossover networks are would need to be matched by the digital filters that you would substitute for them (after removing them from the signal path).
Some receivers/pre/pros specify crossover slopes and some don't. Frequently, it's a second-order (12 dB per octave) for the HPF on the mains and a fourth-order (24 dB per octave) for the LPF on the mains. I would imagine that some receivers/pre/pros allow variable crossover slopes, though I don't have any first hand experience with any (something high-end like the Anthem D2 or the Lexicon stuff...). I know it was spec'd as a second-order HPF on the mains for my Outlaw 990, even though it was implemented as a fourth-order when I measured it. The sub out LPF was spec'd as a fourth-order, and measured as a fourth-order.
As I mentioned before, most HT receivers are crossed-over before being sent to the mains anyway.
Yeah, but that's a different crossover point. In that case, you're imposing a filter at the
low end of the speaker's operating range, which is normally goverend by that speaker's bass driver's natural roll off. There wouldn't normally be a high-pass filter on the speaker's low end (although I wouldn't put it outside the realm of possibility).
So, in a powered sub system, there is no way the slope in the receiver matches the slope in the mains.
Well, there's generally no high-pass filter on the overall frequency response of a stand alone speaker. There are crossovers between each of the different drivers in a speaker system (e.g., between the 6.5" driver and the tweeter), but there's not a high-pass filter on the 6.5" driver at its low end.
If your speaker is naturally going to fall off at, say, 50 Hz, then
you want to impose a crossover at something like 60 Hz. At that point, you have set the slope and the frequency of the crossover via bass management.
Same with the sub. If you turn the sub's built-in crossover to its maximum (basically take it out of the loop), and apply a low-passed signal (via bass management), the receiver has again decided the slope and the crossover point. If the receiver/pre/pro is well-designed, the mains and the sub will be crossed over correctly, the slopes will be correct and the integration between the sub and the mains can become somewhat seamless (with some work from the end user).
Bottom line -- the crossovers applied a receiver's bass management between mains and sub are controlled and defined by the bass managment circuitry. There's nothing else to get in the way of those crossovers (no other passive or active circuitry in either the sub or the mains). The passive crossovers inside the speaker cabinets deal with separating frequencies applied to each individual driver within the cabinet, and are totally indepedent of the bass management of the receiver.
And for most, the mains, sub, and receiver are all of different brands.
Yes, but it won't matter because you've defined crossover point and slope via bass management at points that are outside the operating range of any other crossovers in those mains and sub.
