subwoofer out

Hello, Speakers - Hivi Swans D1200 (No sub-out) -> connected to my amp ifi Zen Dac V2 via RCA -> Connected to my PC My speakers have 2 line, 1 coaxial and 1 optical inputs ifi zen dac v2 has 1 line input I want to buy a subwoofer but I don't know how to connect a subwoofer without a sub-out...

I just purchased a used but pristine Yamaha A-S501. I paired this with brand new Klipsch Reference Premiere RP-600M II bookshelf speakers and my Technics SL1950 Turntable. Digital music is through my Sharp XL-HF102B, which allows me to connect via Spotify/Bluetooth and also the built-in CD...