If the theme uses the_archive_title() to output the archive title it will output something like: 'Archives: Events' on your event list, use this function to just output the title without the prefix.

example.php

<?php //Please do not include the opening PHP tag if you already have one 

function tw_ee_get_the_archive_title( $title ) {

    $ee_post_types = array( 
        'espresso_events', 
        'espresso_venues',
    );

    if( is_post_type_archive( $ee_post_types) ) {
        return post_type_archive_title( '', false );
    }

    return $title;
}
add_filter( 'get_the_archive_title', 'tw_ee_get_the_archive_title', 20, 1 );