The forward slash is
a problem, but it isn't
the problem. It appears that with soundcloud.com you can't build the embed code from the URL.
Here is the embed code for that composition:
Code:
<object height="81" width="100%">
<param name="movie" value="http://player.soundcloud.com/player.swf?url=http%3A%2F%2Fapi.soundcloud.com%2Ftracks%2F6928510&secret_url=false"></param>
<param name="allowscriptaccess" value="always"></param>
<embed allowscriptaccess="always" height="81" src="http://player.soundcloud.com/player.swf?url=http%3A%2F%2Fapi.soundcloud.com%2Ftracks%2F6928510&secret_url=false" type="application/x-shockwave-flash" width="100%"></embed>
</object>
<span>
<a href="http://soundcloud.com/chimpstudio/tes-27-apr">Tes 27 apr</a> by <a href="http://soundcloud.com/chimpstudio">chimpstudio</a>
</span>
And here is the URL for the page:
http://soundcloud.com/chimpstudio/tes-27-apr
Nowhere within the embed code is any identifying portion of the URL. The id of the video (for use in the embed code) appears to be 6928510, but that isn't in the URL.
I don't see any easy way to use soundcloud.com as a BB Code Media Site in xenForo.