(a) We agree on some points and disagree on others. My apologies if I am missing any of your posts, but I went through all your answers in this thread and could not find any figure in dB or degrees. If so please just say me the post number and I will re-read it. As some people seem to believe that anyone using digital can reproduce ANY transfer function exactly with great accuracy and success I find the point relevant.
1. Wilson Audio includes some damping resistors of different values (typically one value around 25 and the other around 30 ohm) that can be assembled in parallel with drivers. As they have high value compared to the resistance of the coil, changing them has almost no effect in speaker response - I have measured it. However it changes sound quality a lot. I have read that one of the effects of the usual L network used to attenuate level in crossovers is also damping the speaker unit.
2. OK
3. AFAIK we are debating why there are no more active designs that are competitive with high-end loudspeakers in this thread. Quality of existing reasonably priced and accessible crossovers is an issue. I am sure that there are many DSP hardware platforms that are suitable for the development of active crossovers that can compete with the best passives. But the lack of expertise to use them and the total cost can be one reason of the lack of enthusiasm of the community, although we have seen high-end solutions from companies such as Meridian, Cabasse, B&O and Backes & Müller.
Although not directly related with this thread subject recently Amir presented us with ARCOS- a SOTA bass management system by Harman. Curiously the steps for amplitude of each setting were very large - I think around 6 dB. However a very clever system managed to get an excellent solution just playing with Hertz resolution, four Q factors and 7 values of delays. I found it great. I think that an innovative approach (please do not ask me which, if I knew I would not be here now!) using the unique capabilities of digital is the way to go for active digital designers if they want to be competitive - just replacing the passive elements of the crossover, and trying to reproduce or ameliorate the existing speakers is not a promising way. All IMHO.
I added numbers in your post when I quoted, 1, 2, 3, to make it easier to keep track of your points. No dB, phase, or worthwhile engineering terms. Language barrier, sorry.
1. The added resistors have an impact at audio frequencies because they affect the signal going into the (inductive) voice coils. They will modify the frequency response as well as lowering the Q of the system as you said (reducing ringing).
2. You could check the website; I will take a look at what the program says if I remember but I have a very busy weekend (concert weekend).
3. I probably misunderstood the thrust of your posts and this thread; my assumption was this was just to list things rather than debate the pros and cons here since there is another thread on passive crossovers. However, the exchange is good. My apologies, long week and I am grumpy today (and have rehearsal tonight so am still many hours from going home after a 12-hour workday).
On the DSPs, I think the problem is not a lack of good DSPs but rather people who understand how to program them (as you said), and good interfaces (ADCs and DACs) on either side of them (my adddition). Plus the lack of desire to work at something like that rather than having a plug-and-play speaker. I suspect those are more the reasons than cost, but I think we generally agree on (3).
All the best - Don