i checked out mj acoustics, in wisbech cambridgeshire, near where i used to live in the early 80s, i hope to get one or hopefully two of their entry level model when i can afford it, their better models look great and different design to the standard square boxes most companies seem to make 
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Well done Brett, scary scale though, bit still nice…! I’ll post mine in two weeks.
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I still need to measure with the correction in place. Too busy enjoying the music.
Keep in mind the graph above has no smoothing applied. Typically smoothing is applied.
Here’s with 1/12 smoothing applied.
Below is zoomed it a bit more to illustrate where one sub is ‘deficient’ the other is filling in and vice versa. Deficient in quotes because it’s room modes causing this variance not the inability of the sub to reproduce the frequency. To me this is the real value of two or more subs. The increased headroom is just icing.
Once these locations and settings are fine-tuned there is no reason to adjust again - no need for app controlled phase etc. These settings can be set by ear but not very accurately, thus one should set them and not change them unless the room changes - my experience and opinion only. I do use several sets of convolution filters that have more or less bass to manage poor recordings or sometimes my head hurts, etc. but I don’t change the subs controls.
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Sure, start with a sub in the main listening position (MLP) and move around the floor to listen for the ‘best’ response. Put the 1st sub there. Repeat with the 2nd sub. If the locations are non-negotiable, skip this step. I like mid-wall opposite or even offset a bit from each other, not near corners, if possible.
A basic SPL meter will help with the gain and more importantly the phase adjustment set. Phase can be used with two or more subs to smooth response in room. We don’t hear phase changes all that well (some argue not at all) so use it to smooth overall response. Using real-time measurement like REW and a calibrated mic makes this part fairly easy and being able to see the effect of constructive or destructive phase adjustments is priceless.
Lots of how-tos for this: https://www.pooraudiophile.com/2017/06/how-to-calibrate-dual-subwoofers-anthem-avm-60-mrx.html
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My point being would I endlessly mess with it because it’s easy? My wife would probably tell me to set it and leave it alone.
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Now you have what I have except I use the “sound of the amplifier” crap as it is so much better than the method you are using now. (IMHO)
And then once you see it sounds better that way you can ponder spending $500 for an upgrade cable for each. Then there is the power cable to consider. (sinister laughter)
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Now I see what you meant! Actually Al, when I first got it, I adjusted it to sound best in my room and for the most part I don’t have to touch the controls at all. Every so often though, I make an adjustment to compensate for a really horrible recording with ridiculously too much bass.
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What I have found with connecting to the amp for the subs is far better coherent sound from the bass. Smoother overall. But you don’t know until you try it. Once I did I never went back and I tried every other way.
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Ok ok ok ok ok ok ok ok 
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Ok ok ok ok ok ok ok 
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I have to share this. I woke up last night, bathing in my sweat dreaming of high level inputs. I started digging and found a typical schematic that should not be much different than the ones we all use in our sub’s. Now think for yourselves…! For once, do not take for granted what everyone else claims. Just follow the high input going thru an impressive array of STEP DOWN RESISTORS (certainly hope that it’s not a transformer in other cases) to then go thru an extra AMPLIFIER and then (by all means) thru a CAPACITOR, because y’all know: THERE ALWAYS IS DC ON YOUR AMP’S SPEAKER OUTPUT…! The signal then follows the “normal” amplification path after it has gone thru a variable low pass filter, which has hopefully in our case NO CAPICITOR in it’s path…!
Then there’s this other thingy that kept me up… Most of you have one of those hot shot BHK fully balanced amp’s right…? Do you know what REL’s trick is to prevent that y’all connect your HOT speaker outputs straight to GROUND…? JUST USE ONE FRIGGIN’ OUTPUT AND CONNECT THE DARK WIRE TO THE CHASSIS…
So as some of you and REL imply that the sound of your amplifier (…?) is mixed into picture, obviously only being SUB 50HZ (…!) I suggest you’re ONLY listening to HALF of that sound… And what half might that be…?
But as I said again: I will try… #nothingbeatsagoodconversation
@Elk point taken and thanks for sharing that detail. However, my speaker system includes an LMS (loudspeaker management system) with room correction. So I place a mic at my listening position and frequencies below 500 Hz are corrected for the most part. I worry about proper integration of sub(s) with my Sanders hybrid electrostats because Roger has gone to great pains to make the TL woofer in these speakers blend very well with the panels (read “the woofers” have very fast transient response). I may take the plunge some day just to try out subs, but very satisfied with my SQ presently so the old saying “if it ain’t broke don’t fix it” applies for me.
I found it was really useful to make adjustments to the cut-off frequency and volume until I thought the sub was well integrated. It took me a while to realize that with a sub, often less is more.
After that I have just left the control alone for the most part, except when the volume and musical program needs a tiny adjustment on the fly. I didn’t develop any new audiophile OCD symptoms (that I am aware of, anyway).
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Bass management can certainly help, but multiple bass sources makes it more likely to actually smooth out the bass response, especially the suck outs. It is just a matter of physics.
But you indicated you are very satisfied. If this is the case, do not touch anything.
Absolutely - the Bassline Blue cable was a great upgrade in my system.
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If you can stretch the budget dual JL Audio! My 2 JL’s have made the biggest difference in my setup! JL Audio subs can be expensive but I can testify the cost is justified. I’ve owned SVS and Rel both great subwoofer makers with great subs but the JL Audio subs are in a different league!
Well, it seems to me that you’re doing nothing more than attempting to disprove everything everyone here is telling you, including Paul himself who has always said that feeding the subs via high level is better and sounds better.
So at this point, I’m dropping out of this conversation. No point talking to a brick wall.
Interesting. I’ve owned both JL Audio and REL, and I’m the most pleased with my SVS sub. Bang for the buck is important to me. Now that I have a sub that goes from 18Hz to 240Hz ± 3dB, (I have it crossing over at 50 Hz) I realize just how much truly low information I’ve been missing all these years. I like that the SVS sub gives me a sense of the size of the room that the music was recorded in.
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Totally agree… which one do you have and how many…?
Pfew, that is fast Chops. I am not that much of a “believer”. I am more an “argument” type of person. That began 58 years ago when I first started asking “why…?”. I still have no regrets doing that. I mean, how else can I afford being an audiophile… Right…? 
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