I'm attempting to set up a 2.1 system, and am having some issues getting my sub to work correctly.  Both of my cards are working correctly - which I can tell by hooking up a set of spare powered speakers to each port and running "Test" - I get the chime for all signals from all ports, so that is good.
 
The problem comes when I plug an actual powered sub (SACS-9) in and attempt to get it to work.  I get absolutely nothing.  I've confirmed the sub works properly, and have tried multiple cables (which have each also been confirmed independently to work properly) with zero success.
 
If someone has had success, could you please provide a list of the exact components you used to go from your surround card to the RCA jack on your sub? 

I have a Nu Audio 7.1 setup with both cards.  I have a pair of Sony SACS-5 bookshelf speakers powered by a FOSI amp, and a Sony SACS-9 powered subwoofer.
For my speakers I have a RCA to 3.5 mini jack that plugs into my FOSI amp, then has speaker wires going to the speakers.
For the sub I was trying a 3.5 mini jack to RCA.

Copy. I'm surprised that this wouldn't be supported on sick an enthusiast card setup.

When attempting to use the sub plugged in on 5.1 and 7.1 it still doesn't work. How would this need to be wired/connected to function with regular music?

Seems like a sub plugged into a sub port should support regular sub usage for music and regular computer use/gaming.

Thanks for your continued followup!
 
I'm not currently plugging in a center speaker, but likely will use a spare set of powered speakers I have for this.  When plugging this set in directly to the CSUB port the left speaker works as center and the right as the sub.  I would need to run a splitter to divert the left for the center and right for the sub signal.
 
I can't be alone in thinking that a $300 sound card setup for a PC should support use of a subwoofer for everything that PC audio would generate (using only the CSUB port)... Not just movies specifically in 5.1 or 7.1.

Hi GeJayGe,
 
Our team is looking into a couple options to bring functionality to the C/Sub port when trying to play audio in stereo.  We have some ideas, but it's going to be one of those things that will take some time.  It won't be a quick update, and there are a number of projects scheduled ahead of it.  It is something we will try, but I won't pretend that you'll see it happen in the next couple of weeks, let alone months.
 
Our configuration (which worked at the time), was to use a 3.5mm male connector split to two female 3.5mm connectors.  One of those was connected to a 3.5mm to RCA cable, which connected to the subwoofer.  The other 3.5mm connector was used with a 3.5mm to RCA cable, which connected to one of the Edifier 980T speakers for the center channel.  I do recall that we had to connect the red RCA to the white RCA port on the speaker (or vice versa) for the center to play audio.  There was some degree of checking to make sure the Sub was set to the appropriate level on the sub itself, and I believe we left the phase switch at default.  Beyond that, we didn't need to configure anything else in the software to make sure the sub output properly.
 
In hindsight, I would have tried a 3.5mm to RCA, and then use a RCA splitter on one of the RCA ports to peel one of them off to the sub, and the other end to go into the main 980T speaker.  Because of the other configuration, one of the speakers would not output audio, so we went with just one.  Mostly, we had little time to get the system setup before shipping it off, so I'm afraid I don't have a best practices suggestion for this.

GeJayGe
A few questions on your configuration:

• "3.5mm male connector split to two female 3.5mm connectors"
  • Was this a splitter that continued to generate two stero signals, or truly split to generate two mono signals? 

It was a basic 3.5mm splitter for stereo, like this: link.  We had a budget, lol.  This is one of the cheapest things we used.  As I mentioned, I'd probably have gone with a 3.5mm to RCA splitter out of the card if I was doing it again.  Maybe something like this: link. 
 

GeJayGe

• "One of those was connected to a 3.5mm to RCA cable"
  • Was this a stereo RCA cable or mono cable? 

I believe we used a regular stereo RCA cable, since we had a few of those on hand.  Then we just plugged one of the two ends into the sub.
 

GeJayGe

• "The other 3.5mm connector was used with a 3.5mm to RCA cable"
  • Was this a stereo RCA cable or mono cable?

Also a stereo RCA cable, both plugged into the speaker. 
 
If you're not familiar with the Edifier powered speakers, the "right" powered speaker acts like the main speaker.  The speaker has an RCA input, along with two outputs via speaker wire for the "left" speaker.  In theory, you should be able to use two of these speakers together for a center speaker (just place the tweeters next to each other).  However, due to the ill-planned cable setup, we could only use the main "right" speaker as the center, as the signal would not pass through to the other speaker (worked fine if tested as front L/R, so it wasn't the speakers).  Moreover, it didn't work in a straightforward manner either.  If the red/white (right) RCA connector was connected to the correct port on the speaker, no audio would play; eventually, we realized that the splitter was probably switching the signal around, so we put the red connector on the white port (or vice versa) and suddenly we had a center channel.


In hindsight, I would probably go 3.5mm to RCA first, then a straight RCA to RCA mono cable to one of the ports on the center speaker, and an RCA mono splitter like this [link] with one mono RCA cable going to the other port on the center speaker and the other mono RCA cable going to the subwoofer.  I believe that's a more efficient setup than what we did.
 
Now, if your center speaker just uses a 3.5mm connection, then the 3.5mm splitter might be the better choice.

I've been scratching my head about this but what about a soundbar for the center with sub out?

Detleg
I've been scratching my head about this but what about a soundbar for the center with sub out?

In theory, I don't see why that wouldn't work.  I considered doing something like that for our CES show.  The main and really only reason I can see that you'd not want to do that is because "soundbars" command a slightly higher price than some of the alternatives simply because there's a big market for soundbars currently.  From a technical or operational standpoint, this seems like a viable option to cover the center/sub option.  Just remember that the main point of a center speaker is to handle a mono signal, so you can usually go cheaper for this speaker.

For those not watching the other thread, I wanted to mention the workaround I posted there.
If you are willing to give up Nahimic EQ (de-select it during NU driver install), you can use the Windows Bass Management audio enhancement to get your sub working. Of course, this is an imperfect solution because it won't work with ASIO/WASAPIexclusive/DSD, but depending on your usage, it might be worth trying until EVGA can implement bass management directly in the NU Audio driver.