In a domestic situation, it's nearly impossible to do such a thing. Here's why:
To reflect a wave (in this case, sound), the reflecting object needs to be at least the same size as the wavelength of the sound you're trying to reflect. A Cona will make sounds down to about 35 Hz, which means you'll need a reflector 5m in size! Make it any smaller, and the bass will just 'wrap around' it.
Even then if you do get an object 5m in size, you'll need to make sure it actually reflects the sound, rather than just passing it on to whatever it's sat on (the floor, which will in turn vibrate and take you back to square one). Therefore, it'll need to be very heavy and solid.
The best way to isolate sound between rooms is to literally build a room within a room, and physically disconnect the inner room from the outer room. This is obviously something you think of at the building stage, and is how studios manage to isolate sound between rooms so well.
I would say I hope this clears things up for you, but it's probably given you a headache! 