What Is The Cra In The Stereos Summer Girl Video Car Audio Question: Subwoofers?

Car audio question: subwoofers? - what is the cra in the stereos summer girl video

So I wanted to install some subs in my bow for a while and watched the models ..... I buy a speaker and then create a forum .... and I do not buy one with a box because they have to be expensive ..... tend then an idea emerged in my head, what happens to the bass amp? If I know a bass amp you buy (that would work with the box and the speaker and all) this? I went to the speakers connect directly into my car and not using the U-boats in the amplifier built in all polling stations ...... professional-looking bass amplifier and speakers are given in the first place ?...... I know the correct speaker impedance 4 Ohms) (must be performed by the stereo, and must be sensitive enough .... But this idea seems feasible?