Very quiet subwoofer/bass from RCA input, fine from front 3.5mm input


Apr 27, 2015
So I have been struggling with a new 2.1 setup for a couple of weeks now and have no idea what else to try.

The setup is as follows:

Amp: SMSL SA-60
Sub: BIC F12, Volume at 5, Crossover at 100hz, set to Dolby Input [not 5.1,7.1, etc].
Speakers: Infinity Primus P163
Soundcard: Creative SB Zx, set to 2.0/2.1 setup, Full-Range Speakers off, volume at 80%

I have a 3.5mm to red/black RCA from the SBZx to the SMSL SA-60 Amp, speaker wire from the amp to the BIC F12 sub, then speaker wire from the sub to the Infinity Primus P163 speakers.

When I use the front input on the SMSL SA-60 from a tablet, phone, mp3 player etc. everything sounds great and balanced. Most importantly, the sub does its thing and I never have it above 5 volume [6 and it is noticeable throughout most of my house].

However, when I use the rear RCA inputs and am playing through my computer, the sub is barely audible. Even if I crank it up to 9 on the sub.

I have:

Fiddled with the SBX Pro Studio options,
Run a single 3.5mm to single RCA input from the SBZx Center/Sub out to the Sub In on the F12 and changed the Software to 5.1 mode while having the amp go directly to the speakers,
Triple checked all of the speaker wire connections,
Updated the Creative drivers,
Uninstalled the RealTek drivers,
Turned off onboard audio in BIOS,
Replaced the amp,
Changed speakers,
Tried different 3.5mm to RCA cables,
No idea what else to do.

Nothing above helped at all [except changed the amp when sound was only coming through one speaker].

I am open to any and all suggestions, thank you for your time.


Apr 27, 2015
I have gotten my desired result. I don't know why I didn't try this before, or, if I did, why I didn't think it was the solution.

I set the software to Stereo Direct under the Speakers/Headphones section.

Everything sounds beautiful and I have the expected output I was looking for.
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