This is a really underrated comment. A 36 dB reduction is a factor of 4000 in power, so if the speaker could output 40 watts of power before the update, now it can output 0.01 watts.

These numbers puzzled me as well. As others said, that's several kW of amp power needed there.

And 126dB is really a lot of sound pressure. In a forest, absent of room gain... My not-so-tiny speakers would require close to 10kW to reach that level.

So that guy probably did a pretty bad measurement. Smart phone mic at a random but close distance?

Oh, if the sound quality really improved, an updated DSP filter could be to blame. If the lower end can push up to 96dB and the upper 112dB, reducing the overall gain by 16dB and adding a 16dB gain to the low end can make for a nicer frequency response curve overall, at the expense of maximum volume (reality is a bit more complicated, but that's the rough idea & what I did to one of my systems).

//Edit

Some seller lists these as having 3x72W on two 10" subs (96dB) and one tweeter (104dB). So yeah, close to 126dB (as promised by the manufacturer) might be possible. I guesstimate that's now limited to <1W?

It's "half" on the manufacturer's 1-11 scale

You have a point. Even if the manufacturers needed to reduce power consumption by a half, it shouldn't have led to a 36dB loss. More like 3dB. So why did they make it so much quieter? This has me thinking that regulation of noise pollution in vehicles might be why, rather than the battery issue.