horn electrical problem

Hi I have a problem with my horn!! the problem is that the fuse keeps blowing. I have disconected both horns put a new fuse in turned ignition on pressed both horn buttons and the fuse is ok. I then do the same with only one horn connected and the fuse is ok,I then do the same with the other horn and thats ok, But as soon as I connect both horns together the fuse blows.There must be a simple explanation but I am totaly baffled hope someone can help