I think I'm going to have to start some serious auditioning. Every sub I've ever heard ruins the music I'm listening to. I have a pair of M60's, and they are a delight to listen to at all volumes, including excessively high volumes. Add a sub, and the experience is ruined, which begs the question: Do all these audio places have their subs set up right, or are subs putting out distorted crap, which people have been trained to accept as good.
This has been my experience. I am not claiming subs are crap, but everyone that I have ever heard sure sounds like it. And if these audio guys are trying to sell product, you'd think the theater room would be set up right, wouldn't you.
