Custom Shortcode + Querying and Ordering Posts using multiple Advanced Custom checkboxes

try this:

$args = array(
    'post_type' => 'speaker',
    'posts_per_page' => -1,
    'post_status' => 'publish',
      'meta_query' => array(
                array(
                    'key'       => 'featured_speaker',
                    'value'     => '1',
                    'compare'   => '=',
                ),
        ),
     'orderby' => 'meta_value',
     'meta_key' => 'speaker_order',
     'order' => DESC,   
    );