Adjust default sizes for embedded content

Adding this snippet to the functions.php of your wordpress theme will let you update the default embed sizes

function wps_embed_size($embed_size){
    if(is_single()){
        $embed_size['height'] = 240;
        $embed_size['width']  = 380;
    }
    return $embed_size;
}
add_filter('embed_defaults', 'wps_embed_size');