Usually 6x9 car speakers are designed to be installed in a very large cabinet, since they are typically installed in the rear deck of a car having the trunk as the rear chamber. Trunk volume is usually at least 10 cubic feet, so the drivers are designed to work well in spaces this large. If you put it in a small box, say 1/2 to 1 cubic foot, then it will lack deep bass and will probably have a huge peak at midbass or lower midrange frequencies.I suggest if you want a portable speaker in a small box, don't use 6x9 car speakers at all. Get a speaker designed to be used in a smaller space. There are lots of round 4" and 5" speakers that work great in small boxes. Some are designed to go in the front doors of cars, because the rear chamber is much smaller. Others are speakers designed to go in portable radios and the like.