Thank you for contacting Slingbox Forum. I am sorry you are having audio problems with your Slingbox in Spain. I would suggest replacing the coax cables to see if they may be defective thus causing the audio issue.
In order to get further assistance, please consult the following link: Contact Sling Media Support . If you are in Spain you can call (091) 375 4529. They may be able to better assist you being familiar with TV in Spain.
Hope this helps with your issue!
Have a great day!
Sling Moderation Team
This phone number from Madrid is NOT working. After 4 months of not solving ANYTHING (they even made change something in the router to have full access to the slingbox..) they told me to send the slingbox back and of course I didn't want any other slingbox after this awful experience so I asked for the monet back. After three weeks and two mails with no answer I'm still with no money and no slingbox anymore. This is so DISGRACEFUL.