Stop by your local home improvement center, electrical supply house, home audio store, or other place that sells wiring and pick up enough "speaker wire" to make the runs you need.
Also, make sure that the wire is rated for in-wall installation. There are certain insulation materials that are rated for in-wall use, many are not.
Unless you're an audiophile who claims to be able to hear the sampling rate of a standard CD and finds it irritating, your speaker cable (even though delivering an analog signal) won't be significantly degraded on an 11m/33ft run.
It's probably more important that you keep the speaker cable away from any mains voltage electrical wiring than the actual wire you use for the audio signal.
If you have a couple of options for wire gauge and the price difference isn't significant and it makes you feel better, splash out a little extra cash for a heavier gauge.
Funny, this is getting down votes, but it does answer the OP's question. His question is about the length of the run, not the purity of the audio quality. As a matter of fact, the OP specifically stated that he wasn't particularly worried about quality loss:
@FreeMan I'm definitely not audiophile, 0,001% loss in quality is not an issue for me.
It seems everyone's voting this down because it's not the "audiophile purist's proper answer". Well, go spend $100/foot on expensive wire that makes you feel better.
This is 100% correct for the OPs desire.
Oh noes, people don't like me and I've lost some pointz, whatever am I to do??