I test the stock Bose subwoofer from my 2011 mazda 3! How loud can it go?
Sub is dual 2 ohm, roughly 80w RMS, 6.5", tuned to around 40Hz, not a bad unit!
Tested using SSA APM X

Results! (spoilers)

Music (Unoptimised) - 116.23dB (52Hz)
Sub in spare wheel - 120.26dB (55Hz)
Port facing corner - 120.05dB (52Hz)
Gained 4dB going from music at max volume to tones and optimised interior.

SSA APM X-
https://store.soundsolutionsaudio.com...

Pendulum- Immunize
   • Immunize (feat. Liam Howlett)  

Sine sweep made by Kuma.-
   / thekirzle1  

Tones made using Audacity-
https://www.audacityteam.org/download/

Thanks for watching!