I wholeheartedly agree with Duke. Some good reading on the subject is found here:
http://www.etfacoustic.com/demoroom.all.html
As well as elsewhere on that site. The documentation there leads to a very strong argument for using subs regardless of your main speakers ability to reach the lowest octaves. It all depends on your room, and the placement options for your mains and subs. It could be that the best place for your mains is not the best place for the subs, so the mains shouldnt necessarily try those frequencies. Always though, this all depends on your ability to tune to subs properly to integrate with your mains.
In my set-up I was surprised that the speaker designer suggested simply orienting one sub 90 degrees in relation to the other. I tried a lot of positions that looked really nice, but this suggestion ultimately gave the best response. Maybe it was just coincidental, since I really didnt have many placement options.
http://www.etfacoustic.com/demoroom.all.html
As well as elsewhere on that site. The documentation there leads to a very strong argument for using subs regardless of your main speakers ability to reach the lowest octaves. It all depends on your room, and the placement options for your mains and subs. It could be that the best place for your mains is not the best place for the subs, so the mains shouldnt necessarily try those frequencies. Always though, this all depends on your ability to tune to subs properly to integrate with your mains.
In my set-up I was surprised that the speaker designer suggested simply orienting one sub 90 degrees in relation to the other. I tried a lot of positions that looked really nice, but this suggestion ultimately gave the best response. Maybe it was just coincidental, since I really didnt have many placement options.