I’m no expert with regards to subwoofer integration, but certainly have been playing with them since the early nineties- and learned over the decades that follow that mains sans sub is a much more coherant system sound.
Until I played with REEQ and things like XT32 (with multiple subs) and Anthem ARC…
ARC is a cut above, but XT vs XT32 can come down to ‘number of subs’…
Top to the tree room re-eq stuff (eg Lyndorf etc) is out of my price point, but certainly going beyond making a frequency sweep smooth, and having setups that can ‘remove room factors’ from the playback- is incredible.
I put the Anthem ARC capable setup into the den to see if loosing preamp quality (absolute) and ADCing my DAC were worthy sacrifices on the path to ‘better audio’
yes and no…
lost a lot of fidelity from one point of view, and gained a stable reference (that was a lot less motivating to listen to, even though it sounded technically brilliant).
My often recommended trick is to ‘steal’ (borrow) the re-requalising surround processor from the lounge room and to briefly install it in the ‘den setup’ (hifi rig)…
Using the rendered graphs generated after a room measure - I can adjust speaker positioning and ‘levels’ using the visual feedback VERY EASILY.
Once I have the speakers and sub integrated to the best they can do -sans modifiying the audio signal- then I consider that the baseline setup for the room… (those playing with REW software would be asking a LOT LESS from it to achieve its’ goal-)
Sometimes it is amazing how much a ‘rear ported’ speaker can alter its lower frequencies with a little extra distance from the wall (happens with toe in, too),…
A room read and reset the speakers will never equate to phase/timing adjusted THROUGH THE FULL FREQ RANGE that modern front end processors can achieve…
… but can massively lower the the fatigue- but of itself will not reveal second reflections and ‘brightning’ of sound though unoptimised room layout structure.
Some of the best installs I have ever had the fortune to listen to have been ‘pure math’ affairs, having been designed on paper (calculating reflections/decay) and are brilliant.
A lot of the math, once we digest it, is straightforward.
Our ears need around a metre of space (timing difference) between reflection ‘layers’.
The second harmonics I hear from the side walls are not time aligned with the ones from the ceiling.
Having my chair forward of the rear wall at least ‘half a metre’ (factoring bounce is greater than a metre), adds another ‘clarifiying’ harmonic…
They clarify the sound if the brain can isolate and identify them… they need to be 1m+ further away…
Once we see a room as a number of surfaces and distances to ‘play with’ this can be quite fun…
And is generally a ‘set and forget’ aspect to hifi setup (work done once and then ‘many years of enjoyment’)
I use Vanessa Maes Butterfly lovers concherto (or whatever name is ‘similar’) for toe in changes as the stage in this piece of music (first track) is so ‘back’ and room reflections really can muddy or clarify this stage setup.
I spent many many hours ONCE listening to the stage change with a few millimetres ‘more’ toe in (/‘less’ toe in)… could change the depth of the stage beyond my rear wall, and with that imaging change, comes a sense of perception as to how wide the stage is etc… when toe in changes the stage dimensions so noticably… reaffirms the value of ‘why we need to set this’.
It is better as a two person task/‘panel’, so long as the testers can be fully relaxed (and have the time) to do the due dilligence…
TL: DR - I love to cheat; and use surround amps in my hifi setup to ‘check the room’/‘speaker and subwoofer integration’ and adjust using the visualised graphs that the room test/calibrate function of modern surround processors allows.
Toe in is best done by listening to a familiar track (and maybe using notes to record findings and tape on ground to take note of the positions)