Do I need all the fancy alignment that is incorporated into the high-end boxes?
Definitely. And it’s not that easy.
I do not use 802D, so I cannot be particularly helpful with recommending sub for them, but I spent enormous time for testing and integrations (including measurements) and one might consider my experience useful.
First of all if you don’t really need them, do not waste time. Otherwise you will spend a lot to choose one that integrates well and then to integrate it.
In general (and this is quite of generalization) subs are good for rooms with less than optimal acoustics, they allow to tune results by introducing more options to position them, but in exchange to a more work required to accurately time align them (it is as painful as accuracy of a pot on sub that usually is not that good).
But the first real hard task is to choose one. Questions that come to mind are: what size, ported or sealed, etc? From scratch I would definitely choose the one offered by vendor for exact mains model if there’s any available. That way you save time by easier integration in terms of crossover and spl levels. I am not aware of B&W offerings for your speakers, but I would check that and definitely go that route (if there are no specific requirements that dedicated gear is not able to fulfil, or dedicated subs are unexpectedly subpar).
If there’s no dedicated sub, things are getting tougher. It’s very likely that independently from vendor of your choice you’ll be forced to find and tune a dedicated crossover (if you set subs to go higher than your mains can- not recommended, but sometimes useful when room has some deficiencies) or at least lpf (if you set subs to start working where mains cut off-recommended in most cases). A real pain. I haven’t found a sub’s built in crossover/lpf that worked well (to match mains factory characteristics) enough for my ears. With this you can go digital, but it will make amplification yet another step of difficulty.
Things got even more complicated if you prefer sealed subs and your mains provide quite high pressure levels. This is where subs size matters, but even then in most cases you will end up with integration that will work correctly at limited range of levels. Closed (EDITED: was ported) subs definitely work better for smaller rooms too, so if you prefer ported designs for some reasons (most people behind critical listening I know prefer closed ones for a reason) but have kind of small room you’re going to have kind of tied hands. On the other hand in bigger room you’re also under constrains- subs setup must be well-thought too.
I have a luck of running triple mains/sub setup that allows me to run mains in their full range with a subs lpf'ed, subs at their whole range with mains with a higher hpf than default (than factory designed rolloff), and mains only. Although all modes are available at a fingertip (my console with monitor controller is custom- it is a byproduct of my previous setup with two separate rooms and separate speaker sets) I rarely run subs for critical listening despite custom filters design (my mains are -6dB at 38Hz by default and my room is quite good: +-3db 20Hz-300Hz with a controlled decay times and no electronic correction). I can still hear the integration in action- it still requires some work, it’s not that neutral as I wanted it to be. I mostly use subs in two cases: when I suspect something is going on when mains are unable to show and when I want to impress some less experienced people (subs are adding a little in bottom when tracks are really well produced with those octaves in mind, it looks like a little more hmm euphonic for some).
The question you might ask why I went route with subs (and why not a dedicated ones for my mains)? This is a good question
. Well, we all have these limited resources and abilities to listen to what we are willing to. I also thought that it would take less time, really.
I think that dedicated subs for my mains are really excellent in terms of integration. Unfortunately I was not able to listen to such dedicated setup in my room. My current setup is more of a workhorse, subs are going much lower (sometimes it’s needed) and I prefer definitely sealed ones. I also don’t think that I would be able to get that frequency response from any reasonable (economically too) real full range mains. It all of course doesn’t end on FR, it rather begins there. Finally, my room was built around this setup and it’s hard to beat argument.
These are my reasons. And experiences.
Good luck with your journey! You’re going to need it.