Room setup

I have a two car garage.  Last winter I blew in almost 3 feet of insulation.   The walls are lined with shelves with bags of smoke pellets and miscellaneous junk. 

I took the old stereo out to the garage.   I mounted the speakers six feet high in the back of the garage.   It's almost a completely square room.  

Here is the thing.  The stereo sounds amazing in my garage.   I can't get that sound  in the house.  I sit just outside the door drinking coffee and listening,  and it's amazing.   Damn, wish my living room sounded that good.  Has to be the room. 
Partly because of the cement slab foundation? That's assuming the floor of the house is a suspended wood structure.
The garage is big. Its not over damped with wall to wall carpet, and all the odd shaped stuff stacked around the perimeter and covering the walls is perfect for randomly scattering the sound. Lots of hard surfaces combined with random scatter, its the garage equivalent of a concert hall.
Yes, I take my inside equipment out to the garage to see what it really sounds like, then take it back in with some disappointment.   I can live with it, but it was an unusual discovery.