Hi
IN our hobby it is difficult to escape dogmas and declaration of faith. The reality is that Integration of subs with mains require flexibility. Nothing is as flexible as digital filters. Analog filters are bound to do much more harms than digital down low ... Repeating down low. I could add everywhere but ... let's leave that fight for another time
There is nothing added in term of circuitry for the Devialet or other Digital DSP to do their things, just processing and in the big scheme of things audio is a low bandwidth application wich is handled with aplomb with modern (and some last century too ) processors.
INtegration means that sometime you have to curtail the top end of the subwoofer response . IOW make sure it doesn't play over a certain frequecy range , many subwoofers do ... so while we concentrate usually on the low pass we forget the high pass. in several instances some subwoofer play loudly up to 200 Hz with often a very jagged and irregular repsonse adding much "muck" to the main response with the resulting "slow" muddy and lack of definition... and that is putting aside the intrinsic quality of the sub in the region of interest that is <50 Hz or so ...
there are many professions of faith concerning the best approach and 4 towers is good given a dedicated and well treated room and luck. Distributing subwoofers provide the best performance in most cases.
Choosing subwoofers is not an easy task: It takes a long time to integrate any subs with mains. it takes a long while to dial them in the room. It takes some education to understand good bass. I am not by any means being pedantic or condescending. Good , clean bass is quite strange at first. Most people haven't heard a clean 40 Hz let alone 20 Hz in their environment. 20 Hz is not heard, hardly so it is felt and it requires some healthy output to be perceived .. at 60 dB of SPL, 20 Hz is so faint as to not be perceived by most people's ears although your walls will likely rattle and things will shake. The problem is compounded by the fact that many subwoofers distort a lot when asked to reproduce 20 Hz at realistic output say 90 dB, > 20 % THD is not uncommon.. It is not rare for some celebrated subs, to output a lot of 60 Hz when asked to reproduce 20 Hz at say 100 dB you would find some serious 60 Hz component at 70 dB SPL which is easily heard. The better subs don't and sound strangely enough at first less "bassy" .. It takes time to understand that and notice the improvement in FR almost everywhere .. to arrive at the integration will test the patience of many audiophiles
The problems are multiple and usually the audiophile tackling subwoofer integration gets to a point where the trade-offs are not worth the results, especially when the person eschew DSP. DSp is not a panacea, not a cure-all but in the realm of subwoofer to main integration DSP is the best tool there is.
O.T.
I have to stop writing , perhaps later. For now we are bracing ourselves.. waiting to suffer from (or hopefully not) the fury of a Cat 4 hurricane moving very slowly ... the South peninsula Haiti, has already being hit with some other are waiting ... It seems to move a little bit of our coast but part of .. We'll see... Discussing with you guys takes the worry off my mind ...