It's Your Choice/prefrence
Adding insulation or placing a speaker in an enclosure usually results in a "warmer Sound" or a sound with deeper or round bass. If U have 4 X 8 or deeper ceiling joists you can make an enclosure with 3 piece of wood. measure the width between the ceiling rafters. Let's assume its 16 in. If you are installing a 6 inch go to your local sterio shop and measure the demintions of a 6 inch speaker. " You dont have to be exact, you are trying to get close to the size of that box. Cut 2 pieces for the sides using 3/4 ply : 5 1/2 inch X 16 inch next, Cut 8 inch X 16 for the top. Screw together to make a "U" shape. Hammer between the rafters using. The drywall of the ceiling makes the front of the box. The box improves the bass and prevents the sound from leaking into the floors/rooms above