Trying to figure out how to get my Subwoofer working with a 2.1 set up on my computer.

I bought two JBL 305P MKII speakers to use as my regular left and right channel speakers. I also bought a LSR310S to use as my subwoofer. It works perfectly while listening to music on my phone and my computer that the bass from the subwoofer sounds good.

When I watch a movie it is noticeably absent or very weak. I currently have it set up with using Male XLR to Female XLR from each JBL 305p MKII speakers to the LSR310S subwoofer. I am then using a 3.5 MM TRS to Dual 1/4" TS Stereo breakout cable from the subwoofer to a groundloop isolater to my computer. Was looking into buying an external DAC like the Topping E30. I use Media Player Classic to watch media. They are at least 5.1 to 7.1 channel files. Is there a setting I need to change?

Codec Tweak Tool > Audio Output > Select Stereo and enable "Include LFE"

Then it will include the subwoofer channel in the downmix.

It is grayed out for some reason. Won't let me click it

Edit: I just decided to reinstall from scratch. Why would I use Stereo with LFE instead of 2.1?

Stereo+LFE and 2.1 result in exact same configuration.

So yes, you can just select 2.1 in your case.

Thank you. it works great now.

Is there a center channel bar I could buy to add to my 2.1 setup for my computer that would go well with my current setup you could recommend?

I don't recommend that because three regular speakers is not a standard layout, and hence not supported by the codecs.

Ah, ok. Is there a way I can convert these speakers and subwoofer I bought into a proper 5.1 completely then?

A proper 5.1 setup would obviously require 6 speakers. Trying to emulate it with less speakers will not give good results, so a waste of your effort.

Sorry, I wasn't clear. What speakers brand and model and other equipment should I buy to turn it into a complete 5.1 setup for my computer that would go well with each other?

5.1 speakers should be bought together (as single product with 6 speakers).
I'm not 100% sure but I don't think you can get separate speakers to work nicely together

I don't have any advice for brands of speakers. I know nothing useful about that.

ok, Thank you then for all of y'alls help. Happy Holidays