Actually, I do know how to set up a system and from my experiences, anything above 30 hz and systems start to sound more like a pa system. The most important part for me in setting up a system is main speaker placement. Then, where do I have my components. Sticking a huge subwoofer in an area close to my other components causes problems. Ideally, they would be on a side wall but that is a luxury in my view. Subwoofers are made to reproduce low frequencies, not be a midrange. If my speakers only go down to 50 hz, I cannot expect miracles. I will never get the soundof a true full range speaker, but their are compromises there two. Most full range speakers are rather large objects so they need a larger room. Speakers that go down to only 50 hertz are not made for a large room. So a sub crossover set at under 30 hertz should give you more than enough low end and integrate fairly well with main speakers down to 50 or 55 hz.
