The MTX Jackhammer is one of the largest (if not THE largest) subwoofer loudspeakers ever manufactured. It is often used in automotive applications, where it needs its own dedicated alternator, battery, and capacitor bank. It is very large and weighs several hundred pounds. It is in fact so large that it will not easily fit in a normal car. It is best suited for minivans, SUVs, Hummers, and the like. Speakers this large are often considered overkill for car audio.
My friend just got an MTX Jackhammer for his riced minivan.