Long answer: If you replaced the sub with one that has its own amp, and RCA style plugs, then maybe. You could also try getting 3.5mm to RCA adapter cables, but my guess is that you'd be less than happy with the results.
Essentially you have your desktop speakers intended for use with computers, and speakers intended for use with a receiver or some kind of amp. Trying to mix the two rarely works out well unless you really know what you're doing.
I personally have my sound going to my hi-fi. This necessitated that i get three 3.5 mm jacks to six RCA outputs. I can tell you that it sounds brilliant! Theres really not much loss in quality, and also my hi-fi speakers look much better than those puny desktop speakers. So back to answerig your question. As long has the sub has access to an amp of some sort, whether built in or external, it should work, if you could get the signal from the pc to the sub using converters. But as far as powering an unamplified aub directly from your pc, nope sorry won't work.
Thank you guys. The thing is that I will have a reciever but in a few months and I want to connect the pc to the reciever and then to the speakers, I want to test if there is difference If I skip the reciever.
But I don't know much about this. What do you mean with an "amp"? I mean I know that stand for amplificator, but why I need one. Sorry if the question is too noob.
Haha no problem. An amplifier boosts the power being sent to the speakers. I'm not entirely familiar with exactly how an amplifier works, but basically it reduces the amout of power needed to make the sound. Like let's say you have a 12v battery connected to a speaker. In this configuration u barely get a peep from the speaker. Now, you connect the battery to an amp, and the amp to the speaker. Now you get a crystal clear sound.
Most speakers are designed to work with an amp, or have a built in amp. I wouldn't try running speakers that were designed to work with an external amp, without an amp. You might damage something.
ok got it. So the best option is wait for the reciever I guess, right?
Absolutely. If you wanted you could get a cheap set of desktop speakers, maybe a 2.1 set, to tide you over without any kind of significant cash outlay, but I wouldn't bother trying to connect speakers intended for a receiver to a computer. Once you get the receiver however, make sure to connect it via that toslink connector you have on your motherboard. That leaves open the option for true surround sound, not just upmixed stereo.
You can connect your onboard audio to speakers and subwoofers directly, via spliced 3.5mm cords. The cones will move and sound will come out; the only problem with that is the sound level will be extremely low, nearly inaudible but measureable.
with the optical output you do not need to use an HDMI output for sound and I do not know of a reciever that has an HDMI input.