Eh hem!...Subwoofers... What do ya know?

Just wanted to add that using the downloadable calculator here I think the measurements I entered fairly well replicate what I am hearing.

For fun I put in specs for speakers I am interested in and they really do add seem to alleviate the issues.

Assuming this calculator is symbolic of my issues of course.

I didn't enter what Focal says the low frequency roll off is, but rather Stereophile's summed measurement at -3db

redmosessc10 posts12-16-2019 11:35amEverytime i hear a rig with a sub for 2 channel, i can HEAR the subwoofer, its not a balanced / natural tone to my ears. I know this can be tweaked but i have yet to hear one that i liked. Golden Ear, Martin Logan and other speakers that have self powered subs do a better job at integration than an external unit but i still always HEAR a sub in the room. I do have a sub for cinema but when listening two channel i prefer a passive speaker configuration.

I agree.
 
Speakers with built in subs can have better speaker to sub integration. Unfortunately optimal speaker locations may be a poor choice for subwoofers with extra low frequency capabilities exciting a rooms bass modes and nulls. Raising the speaker subs low pass filter helps but defeats the subs capabilities of producing a surprising amount of recorded ELF.  

Multiple stand alone subs can reduce or eliminate room interactions but that's only one aspect of subwoofer integration. Unless there is some means of comprehensive multi-band parametric frequency equalization, Q, and gain control through the crossover region without using high pass filtering, matching the stand alone subs to the speakers presentation is impossible.
An alternative is to select a hard crossover point and reduce the gain until the subwoofers noticeability is reduced which many consider state of the art. Its not.

n without using high pass filtering, matching the stand alone subs to the speakers presentation is impossible.

@m-db is not impossible, on my specific case the subs and the speakers are manufactured by the same company, speakers crossover and speakers themselves are tuned to the 4 subs and integrated with dsp amps.
The beauty of it is you can follow the designers integration recommendations or you can try to play and better the designers intentions (not that you could have a real chance to improve it much) tweaking dsp etc.
As and added convenience 2 out of the 4 subs share the same footprint as the speakers so no extra space needed. I have to add that I personally like the idea of separate subs from the speakers better in terms of location, true you need some extra real estate but not much and you have more options to locate the subs, you can even tweak with the vertical plane and locate 1 or 2  in your ceiling if you are up to the task (I am not)
In the case the designer is not the same you still can find speakers with proper integration, most speakers are ranged starting at 50 hz 60hz you could use dsp to match these values as well or modify the xover like you mentioned

Erik said it best, " Hard to integrate well. Glorious when done right."

I've used subs for many years now, mostly to augment stand mount two way's.  Up until I had my current setup, my system had to work the best it could in our living room, with minimal options to make changes to the room to accommodate the sub.

Now that I have a dedicated room, one that is much larger than the living room and whose dimensions are nearly square, integrating my current subs was incredibly frustrating!  Before applying room treatments, the only way to minimize the room adding a single note to whatever the bass line in the music was, was to position them behind the sofa, in  approximately the mid-point of the room.  The problem with that was the "disconnect", where the performers seemed to be in front of the listener, but the impact of the low bass came from behind.

I eventually was able to "tame" the added "single note" by purchasing a calibrated microphone and REW, to help place 10 bass traps.  Now when I listen, as my wife says, it's in my "padded cell".

pretty solid article on sub integration.
https://jlaudio.zendesk.com/hc/en-us/articles/205061040-Adding-a-Home-Audio-Subwoofer
I am preparing to integrate a pair of JL E112 subs in my system...showing up in a few days...
I will first try high level connection right from the amp terminals to the subs HLE input...then try a Jensen Iso-Max speaker level to line level isolation device...I think ultimately though the JL CR-1 (or similar) the ideal solution for integration mostly because the latency can be better controlled;

I initially plan on placing them like this (on the insides of the speakers);
https://imgur.com/Paj46Ti

feedback welcome!