I meant to say revert Sonos sub back to previous sound signature 

I’m not sure there’s a way to revert firmware (the software that runs on the Linux computer in the Sonos device). I’d probably mess with the sound profile settings in the controller for the device. It shouldn’t be that far off. I’ll admit I don’t have a 3rd gen Sub, though. And I wouldn’t trust much I Google about Sonos, honestly. There is so much disinformation out there, the ‘AI’ tends to pick up on it, for some reason. 

I love Google answers these days.

I'm also the guy that said "Go for it, I'll hold your beer." back in the day.

Aside from intentionally or incompetently poisoned information most searches are very poor at sorting information that applies to older hardware/firmware/software from current offerings. AI assisted answers actually seem worse in many cases.

Be careful what you trust.

I have a Sub4.
Yesterday I watched Mission: Impossible – The Final Reckoning. I noticed the bass was more pronounced than usual, actually quite a bit and in a cool way :)
Today I searched for updates and there was one just for my Sub4.
Now it's updated and we'll see if anything has changed.
Version 17.2 (build 90.0-68120)

Guys, FYI…

What Happened

The team identified an issue that unintentionally increased bass output for some Sub (Gen 3) and Sub 4 users. This was not an intentional tuning change. This change, resulting in an increase of 6dB to bass frequencies, could lead to rattling and sound distortion like clipping - depending on how much the Sub Audio Level was already increased. Some of you have already experienced this and posted about it. To ensure a consistent sound experience across all Sub generations, we’re reverting the sound profile to its original state.

An update is now available that restores the intended tuning. While we’re not pushing it automatically (yet), you can update manually in the Sonos app:

Settings > General Settings > System Update > Check for Updates

https://www.reddit.com/r/sonos/comments/1mtmba5/sub_bass_output_trueplay_issues_following

Hmm, looks like I just need to turn up my bass to get the same wow feeling :)

Sub gen3 it’s been 4 days now after Sonos update to revert subs back to previous settings all I can say is what have you done my subs are nowhere near as good now I used to have sub level on 5 it was perfect now after update to revert back I have it on level 8 and still might have to turn it up 

if there is no improvement on this in the near future Sonos is going to loose a loyal customer I will sell all my equipment which is worth £4000 and go with something else I’m sure I’m not the only one thinking this just listen to what the customer wants and provide