I have been having the exact same issue, sorry to resurrect an old question, but the answers on here aren't quite usable on 13.10. So, I went messing about in the Pulse Audio controls and I figured out that there is a way to do this similar to what Sergey provided.
You can no longer go through the default sound settings, you have to change a setting within the PulseAudio Volume Control application. If you don't already have it installed you can run
sudo apt-get install pavucontrol.
As for how to change the default sound going to wherever (I know it works with GTK-RecordMyDesktop), read on.
You have to actually have something recording audio, such as GTK-RecordMyDesktop, otherwise you can't access the setting that you have to change. Here's a screenshot of the PulseAudio Volume Control window prior to the start of the recording:
Now, I started recording via GTK-RecordMyDesktop and you can see the screen has changed:
You have to change the drop-down menu from
Built in Audio Analog Stereo to
Monitor of Audio Analog Stereo and it should record the sound that goes to your speakers, at least it did for me. Beyond that it is an Intel sound card, I don't really know any details about my sound card, it's in an old Toshiba Satellite A105 laptop.
Hope this helps someone!