disabling a blown speaker

Not that I’m aware of, no. 

If you can get to the wires for that driver, either from the rear where they are exposed or from the front where they may be visible or you may need to cut the cone material to get to them you can snip either or both and disable the driver.

You might want to put a bit of foam over it to keep it from vibrating from pressure from the other drivers.

Removing the driver and finding something close to it to use as a replacement might also be a possibility. If the sound is too far off you could always revert to disabling it.

There was a couple of videos on this on YouTube where they bought replacements from Aliexpress to fix their soundbar.

Not sure if this helps or not

I had the same thing happen. I contacted Sonos and they wouldn't offer me any repair options or any recommended third party repair services. 30% off wasn't going to cut it so with nothing to lose I opened my soundbar. You need to pop off the little gray rings on either end that are held on by double-sided tape. Once these are off you'll find four screws on each side. You can remove them and then remove the screens. Once the screens are off you can pop the clips to remove the black portion of the cover. Once that is off you will have access to all the drivers. I quickly determined which driver was damaged. There is about a 1-in tear in the foam surround. At this point you could easily take the four screws off that hold the driver in place and disconnect the driver from the unit. Or you could do what I did and use some RTV gasket maker to patch the tear in the surround. It took maybe about an hour of delicate work but it works as good as new now.

Pretty terrible service on sonos's part. I wasn't even asking anything that was free. Just a way to keep my unit going without having to pay for a current unit That even after a discount will cost more than I paid for my play bar. Seriously not cool. If they could provide a replacement driver for a reasonable cause this repair would be pretty straightforward and take less than 30 minutes. 

Good luck figuring it out. RTV gasket maker is readily available No more than about $10 for a tube.

It’s the lawyers.  The liability involved with encouraging a customer to open a piece of electronics comes before any stated customer service goals. 

Perhaps but I'm not buying that excuse. And, even if true it doesn't explain their inability to offer a  repair service or at least contract with the third party repair services. Not offering repairs, or repair parts to DIYers or authorized service centers seems to fit well with their business model.....Planned obsolescence

Also, internal components for plug in electrical equipment are available across many industries. I don't know why a Sonos speaker would be any different than something like a vacuum cleaner, a computer or a refrigerator, which have readily available OEM parts.

Not many companies offer repair services anymore.  At least not for electronics.  Even for warranties, they issue a replacement, then refurb the return for issuing as another replacement.  My suggestion is to seek out a small appliance/electronics repair shop (which are also going the way of the Dodo).

That's true but they exist and many still contract with third parties who can offer repair services.

I repaired it myself with RTV. If that doesn't work long term I'll open it back up and order an aftermarket driver. 

Sonos could do a lot more to elevate their customer service in anything that resembles an attempt to keep their customers loyal. They're choosing not to.

There are workarounds but there shouldn't need to be.

I’m telling you, as a software engineer who deals with embedded hardware all the time, it’s the lawyers.  They are scared stiff of encouraging the opening up of something which can be connected to AC power.  Matter of fact, I’m surprised they let this and other self-repair suggestions stand.  But there is a disclaimer in the TOS, so I guess the lawyers have it covered. 

If true, that only explains their unwillingness to sell parts directly to the consumer. It does not explain their unwillingness to authorize third party repair services.