Yea its what is called an infinite baffle or free air setup. Your trunk has to be completely sealed from the cabin and you have to have speakers made for the setup. They can get loud and have great extension, but you need alot more power and usaully more woofers than you would use in a regular boxed setup. These are very popular in home theater setups using the attic or basement as an enclosure. But they also use 6 or more 15's and a ton of power to get their volume up