sE Electronics X1S Studio Bundle X1 S with Acoustic FiltersE Electronics X1S Studio Bundle X1 S with Acoustic Filter If you're recording in a non acoustically treated space (bedrooms, closets, etc.), a Reflexion Filter helps keep your signal clean without the sound of your room around it (learn more here). The X1 S Studio Bundle has everything from the Vocal Pack (below), plus our simple and effective RF X so you can record anywhere you want. Contains: X1 S microphone RF X Reflexion Filter sE Isolation Pack