a friend with an old, well used Pre and post filters. Despite my best efforts to keep both clean, I always noticed that the suction power wasn't what it should be and that the vacuum was louder than other similar models I've used before. After my pre-filter fell apart during a stressful session I decided on a new set and holy beans, I'm glad I did. The vacuum cleaner runs like new, 50% quieter and my carpets thank me. I can't believe I didn't do this sooner!