most of what I’ve seen here about the Forscan sub settings is subjective, and I believe it was
@dhmcfadin who indicated the for scan changes weren’t effectual for bass roll off. Even if it were to do something it wouldn’t eliminate bass roll off, it would maybe make it less.
I’ll happily defer to someone who’s got the b&o system here.
You can save money by doing it right the first time, but unfortunately it’s not a cheap buy in. Best bet is to redo the stereo all at once.
Again, even if you get a shallow mount sub to work; you could probably just re-purpose a ’17 or older sony sub enclosure, you’re limited to about 300w max for that class of sub. That’s enough for about 20-25w rms ... maybe. Factory sony system was 25w ... allegedly.
By the time you’ve done this mod, you’ve spent probably 350 ? in parts. don’t. If you had a ’17 and were on a pretty strict budget I’d possibly think differently, but you’re not going to get there or close with just a sub and amp.
I’d suggest starting out by checking out the under $500 thread in the audio section. Pickup the zen, big @ss battery home runs for the amp(s), sub and box.
if you need the rear area for storage, MTI / Mobile Toyz makes a behind the seat enclosure they sell loaded for about 1k. I have a single 10” JL x 1x500w JL amp. It’s great. If you buy once / cry once, you’ll save in the long run.
I didn’t think I would need to redo the system at first, but one trip on the highway with the windows down and I couldn’t hear the sony system at max volume. At max volume, it didn’t really sound good, then I started noticing that some music was just bad sounding due to the signal... “mixing”(?) the guys at Ford did. I did the upgrade in stages with sub/amp first, then speakers and dynamat, and finally new amps/sub/enclosure and signal processor. I didn’t budget for that big of an upgrade at first, so I spent some extra - like the kicker 8” in the stock enclosure, to at least make some improvement until doing something more significant. Once I had some spare pennies, I followed advice of others here.
I ended up doing
signal processor (DSR1 for me), battery home runs for ground/power
Morel components up front, replaced the tweeter in the pillars with the component piece, wired from the crossover.
left the rear door pioneers in place.
MTI sub / amp
about 75w to the 4 main channels.
adjusted a few times to get sound close to where I want it.
I’m probably about 2500 all in and did the work myself. Total would’ve been about 400 less if I’d done everything at once.