Sub In The Fireplace

Thanks for the responses... Rives, I guess I should have been more specific. But, yes, the fireplace is actual brick, and sits on the same foundation as the rest of the house which is a concrete slab. As far as the leveling jacks... are you suggesting this as a method to couple the sub to the concrete (in a sense)? Or simply as a way to cover the flue?

Sogood51, I wasn't sure if you were referring to me or not...
"I'm not sure that the center of the rear wall is the best place for a sub".

The sub is in a fireplace that is in the middle of a wall which one would face when listening to music.

And Flex, I see what you're saying... but I can't say that I've run into that same problem.

Sorry, should have read, center of the front wall. I need to start reading my posts over more often.

Sogood,
I measured my room response before, during and after treating the fireplace. Placing absorbers or diffusors inside the fireplace cavity, or covering the front with glass doors and partially treating the exterior did not work either. 8' tube traps do work.

Vectorman, if you haven't found the problem so far, then you probably don't need to worry about it.

By the way, I should mention that my main speakers at the time were rear-ported, which probably exacerbated the energy distribution into the fireplace behind the speakers. But Vectorman didn't mention what his main speakers are, and IME the speaker radiation pattern affects some room acoustic problems.

This is the best thread title I've seen in a long time! My suggestion would be to stuff the chimney with fiberfill and turn it into a giant transmission line by opening the flue... ;^)