Try using the regular angularFire service, and specifying the type of your single object:
app.controller('ctrl', ['$scope', '$timeout', 'angularFire',
function($scope, $timeout, angularFire) {
var url = 'https://ex.firebaseio.com/stuff';
angularFire(url, $scope, "obj", "");
}
]);
Note the 4th argument (" " means string, you can also use booleans, numbers, objects and arrays).