Are these internal system speakers? Or where are the speakers connected to, exactly?
I'm guessing that you're probably trying to use two different audio interfaces at the same time (Tascam + onboard computer sound card).
In this case, since you are using Windows:
- You can either try using WASAPI (shared mode) as Audio System in Reaper and select the available inputs/outputs
- Or try using ASIO4ALL to make an Aggregate Device of both and use this as Audio Device in Reaper:
https://www.image-line.com/support/F...s_asio4all.htm
If you have external speakers, I'd recommend to connect them directly to the Tascam, if possible (so you're only using one audio interface) ...