May sound like a dumb question. But what is the difference between the different series of speakers. Maybe I don't mean difference. Is it just that each yr they give the speaker a different series letter. I have R50s. But I see RT, FX, LS...etc. Does that mean my speaker is do much more inferior or just an older model being phased out. Sorry for such a dumb question. Just trying to sort out all the different types. Thanks for any help you can give. This forum rocks.