Why is there such thing as a mandatory firmware update for a set of speakers? Now I'm not an audio engineer, but frankly I would never purchase hardware that hostile to user agency.
I can see a mandatory update in the form of legal requirements. For example I think Apple had to implement headphone safety limits in some countries leading to very frustrated customers .
Often, including in your example, "legal requirements" just means the risk-adverse desires of the legal department, which doesn't really address the core concern of why a company should be forcing users' devices to implement the company's desired policy post-sale.
Furthermore in the case where there really is law passed that mandates device firmware be updated to certain functionality, the ability of the manufacturer to force that update onto an end user should be viewed as a security bug in the original firmware.