To install a subwoofer, you can change the complete stereo system and add an amplifier and a crossover or you can use the stock crossover on your Bmw E34/E32.

2 way components speakers are a set of 2 tweeters and 2 woofers, used in conjunction with a passive crossover. The passive crossover takes the signal from the amp and direct it to the right speakers: tweeter signal and woofer signal.

Let's install a set of component speakers. It is the same procedure for just changing speakers. The bigger speakers you can use without major modification are 6.5", they need a little bit of modification for the front and rear. I run 5.25" front and 6.5" rear component system JBL.

Amplifier / subwoofer

http://albums.photopoint.com/j/AlbumIndex?u=1114759&a=9311971

Except I have a 15" Orion that needed a bigger box. I knocked out the metal plate that covers the opening and put some rubber tubing around the edge (to keep from getting things caught, cut, or ripped). I then pushed the box right up to the opening. I'll take a few pics tonight and post them tomorrow. I promised pics earlier, but never followed through, sorry. I also bought some black speaker cover fabric and put that behind the back seat back to cover the hole. The armrest really needs to be down in order to get the bass response. It's a tough judgement call to put the sub in because in hindsight, you really have to tear at the car and all it does is cause rattles anyway....oh well, time for some dynamat!