[marcmicalizzi]

Friday I added speakers to the rear doors of my 3 series with base audio. I had already redone all the other audio in the car and had amplifier in the trunk to connect the speakers to. I used JL Audio C2-400s for the speakers which are almost a perfect fit for all except under seat speakers, with only a small gap which can be filled any number of ways. I couldn't find any instructions or examples of this anywhere online, so I thought I'd share a few pictures and instructions for cutting through the door panel, installing the grill, and installing these speakers in a way that looks stock and is very clean incase anyone else is considering doing this.

First you need to remove the door panel, I didn't take any pictures of this, but it is done in the exact same way as the front passenger side door, except with one fewer torx screw under the trim panel. Disconnect the door handle and power windows from the switch, and you'll have your door panel off looking like this:


You can see here that despite not having a hole for a speaker, there is a clear place for the speaker to go. This means no measuring or spending effort to make the speakers in the same position on each door I used a utility knife to cut through it, pushing into the door panel with it along the circle, and then cutting slightly outside the circle in each of the slots on the outside of the circle for the speaker cover to clip in to. For my car the part I ordered was 51 41 7 144 553, however obviously it depends on your trim. Also obviously the leather needs to be cut as well, I cut through the middle of the new hole, to the edge from the inside, then from the outside i cut around the edge of the hole. I didn't remember take any pictures of the hole before installing the speaker cover, but after the speaker cover is installed in the hole it should look something like this:



Now unlike replacing speakers in the front doors, or if you already had rear door speakers with a top hifi, there are no bolts here to screw the new speakers on to. Since the speakers I selected have 4 bolt holes instead of 3, this works out well for me. With the C2-400s, it comes with 8 screw clips and many different screws. Among these screws are 4 very short screws which I used, and because I also had bought these for the front speakers I had additional screws of the same length (approx 5-7mm long), but I would imagine a hardware store would carry the same screws.

Again I forgot to take pictures at this point, probably because I managed to cut my thumb open on the knife. Be careful guys, they are quite sharp

The board paneling of the door is in 2 layers, which allows the back side screw clips to be placed in between the two layers allowing them to stay in position nicely while you put the other clips on and screw the speaker in.

It would also probably be a good idea to use something to seal the small gap on the outside of the speaker, as the C2-400 is about 2mm less in diameter than the hole, for this weather stripping, as in other howtos might be your best bet, I used hot glue myself, but that may not be the best solution for everybody.

The end result of the speaker installed before putting the door back on the car looked like this:


After this you will need to run the speaker wire through the hose between the chasis and door, to your amplifier and solder it onto the speaker. Again forgot to take pictures at this stage, sorry about that guys, but it is done the exact same way as would be for the front doors, reattach the door panel, rinse and repeat for the other door, and voila, you now have rear door speakers

[djkevinnn]

Great speakers, I loved my C2-650's and the component C2's when I had my 03 Maxima. I considered putting the C2-400's as replacements in my doors, but at 35 watts RMS, it probably wouldn't be worth the hassle. I think I'll just eventually ball out and go with the C5s

[marcmicalizzi]

Originally Posted by djkevinnn

I considered putting the C2-400's as replacements in my doors, but at 35 watts RMS, it probably wouldn't be worth the hassle. I think I'll just eventually ball out and go with the C5s

Actually with the C2s in my car it is quite loud, at full volume it is pretty deafening with little to no distortion, the only issue is that you really need to have a high pass filter on them as the don't handle a lot of bass at high volume that well. The main reason I went with the C2s over the C5s is that I have the base audio in my E90, so I have no place for tweeters and as such a coaxal speaker was my best bet. But with a subwoofer in the trunk and the 8" under seat midbass drivers, it sounds great. I put a ~150Hz 6db per octave high pass for the front door/center speakers, with a ~500Hz 6db per octave low pass for the front midbass drivers, and then used the amplifier (JL Slash 300/4v2) high pass filter for the rear channel (subwoofer is on seperate amplifier, with low pass filter, hooked up to rear channel, but seperate from the rear channel's high pass filter obviously).

[bmw325i]

Your high pass for the door speakers and low pass for the underseats should be the same frequency.

[djkevinnn]

Originally Posted by bmw325i

Your high pass for the door speakers and low pass for the underseats should be the same frequency.

Not necessarily. The high pass for the door speakers should be the range of frequencies that you only want those drivers to play. In this case, we want no where nearly as much low frequencies getting to those speakers. But with the underseats, we want to get not just sub bass out of them, since he has a dedicated subwoofer in the trunk. The underseats are providing more of a mid-bass set up here.

[bmw325i]

Originally Posted by djkevinnn

Not necessarily. The high pass for the door speakers should be the range of frequencies that you only want those drivers to play. In this case, we want no where nearly as much low frequencies getting to those speakers. But with the underseats, we want to get not just sub bass out of them, since he has a dedicated subwoofer in the trunk. The underseats are providing more of a mid-bass set up here.

Your low pass for the underseats is way too high. That is bringing down the soundstage and also you have 2 completely different types of drivers playing the same frequencies.

You should have the sub playing up to around 60hz the underseats from 60 to around 150 or 200 and the door speakers from there up.

[taibanl]

Originally Posted by bmw325i

Your low pass for the underseats is way too high. That is bringing down the soundstage and also you have 2 completely different types of drivers playing the same frequencies.

You should have the sub playing up to around 60hz the underseats from 60 to around 150 or 200 and the door speakers from there up.

+1

Even if your underseats are playing that high, youre going to lose more in destructive interference than you will gain.

This has been beaten to death in this forum

[kaigoss69]

500hz is way off and the 6db slope makes it even worse. You can probably hear 2khz tones from under the seats, not good. Likewise, the 6db slope for the midrange is too shallow as it sends too much low frequency info to these particular mids, which really should not see much below 100hz as they have a fairly high fs.

[cdgatti]

OP, I'll let the other guys sort out your crossover frequency issue. I am wondering about how you have these hooked up to your amps? Are they playing the rear channels? Do you also have rear deck speakers playing the same thing? Wired in parallel or series?