Very possible.
Fungua subwoofer. Hapo nyuma kuna ile transformer yenye hustepdown 230V~ to around 12v-30v~. There's a rectifying/converting circuit that turns the smaller voltage into DC. If you're in luck, this final voltage is indicated huko ndani Kwa hio kacircuit.
If it is 12V, ruka hio circuit ya transformer uconnect battery yako kwa + na -. Sasa tisha wanakijiji na ile ohangla unataka.