Loop sound from the middle to the end

Nevermind, I found a solution on my own. If you are interested this is the method:

 IEnumerator PlayCustomLoop (AudioSource sound, float endIntro)
     {
         sound.loop = false;
         float l = sound.clip.length;
         int t = 0;
         sound.Play ();
         yield return new WaitForSeconds (endIntro);
         t = sound.timeSamples;
         yield return new WaitForSeconds (l - endIntro);
         LOOP:
         sound.timeSamples = t;
         sound.Play ();
         yield return new WaitForSeconds (l - endIntro);
         goto LOOP;
     }

Unfortunately you have to know first the value endIntro, namely the time in which the sound has to start the loop. I hope this can help you.