Want to add Sub to stock unit [Archive] - Bimmerfest - BMW Forums

: Want to add Sub to stock unit

07-24-2007, 07:53 PM
Im pretty good with audio installation but theres a problem.... BMW's audio wiring. I dont want to change the headunit or the speakers. just add a coupl of subs and an amp. i have a 01 740iL. I can do all the wirign myself but how can i wire the amp to the stock head unit to give the amp the sound signals thru the rca's. do i have to splice in to the rear speaker wires to get the signals? id prefer not messing around with the stock wiring as the return current from the sub amps could screw the head unit or the stock amp.

08-02-2007, 09:50 PM
Darn right! That's what fuses are for :) Just wire it all in, although you will have to spice and run wires, and -- don't run them off the rear speakers! Run them off the head unit!

Forewarning: the head unit is a pain in comparison to domestic vehicles when it comes to disconnecting the wiring harness; although once you know how it works it's pretty easy.

08-07-2007, 08:50 AM
I have the same car. I have been playing with my stereo a whole lot recently trying to get it to sound right. For just adding subs, get a high wattage capable line output converter (LOC). Connect the LOC to the sub wires in the rear deck. Then connect the LOC to your amps. I am amping a full range singnal, which is a huge pain in the ass to get. But the subs were easy. I will note that the trunk is heavily sound proofed so you will need some serious power back there. I have played around with all of the speaker signals, and the woofers found in the doors have a fairly high crossed over signal. I would definitetly just snip the wires from two of your subs in the rear deck and use that signal for your amp.

08-08-2007, 06:45 PM
thanks for your replies. Ya i already bought an LOC. its from PAC model TRUNK-LOC. i can adjust the wattage on the signal with this LOC so i think i should be fine. it goes up to 8 volts, more than enough. thanks

08-25-2007, 11:06 PM
He guys i finished my setup ill post some pics later. i got a ?. i think i may have made my box bigger than i needed to. Would filling up the box with some poly fill help reduce volume and help the subs hit harder? thx

08-26-2007, 11:22 AM
If the box is too big, you can screw blocks of wood inside the box to decrease the volume. Polyfill will have the opposite affect. It makes the box seem larger than it is.

08-27-2007, 11:59 AM
How does it sound? Do you have a good amount of volume coming though to the cabin? Or is that bullet proof trunk trapping most of it? What kind of equipment are you using? I am just trying to get a comparison to make sure that I am getting everything out of mine that I can.

08-27-2007, 02:19 PM
i have two alpine type-r 1242ds with a cadence txa-1000d amp. the subs are loud inside the car and i like it. there is no complain from me about the loudness of the subs inside the cabin. some songs the bass hits pretty hard but i think that these subs have more room to hit harder. i made the whole thing into a custom setup. it looks like sex :D. lol

I had a question. My trunk rattles like crazy and its not the license plate. its the entire trunk itself. i can push on the lid hard and it wont rattle a bit, its perfect that way. but obviously i cant keep it like that while im driving. are there any solutions to this? thx

anyway i have some pics posted:

o and the second picture is not completed yet. I am actually engraving a picture i drew with a sharpie onto the wood by burning it on with a soldering iron/wood burning iron.

08-27-2007, 03:57 PM
Nice work. Gotta appreciate a trunk full of bass. Mine rattles too, but its not too bad. I cant hear any of it in the car. I have absolutely no rattles in the car, sounds real tight. Im not sure what to do about the trunk rattle. Im not sure I would waste much time on it, its probably body panels vibrating.

Mine will go real loud too, but I feel like the signal coming from the DSP system sucks because it seems to be enhanced a little at low volume and limited at high volume. I can crank the gain to get it to be nuts, but I am constantly adjusting the bass depending on the volume. Do you have the same issue?

Pics of mine below. 3 JL 10w3v3 off a JL 500/1. I always thought having 3 10s would be sweet. The picture is a little old and I have since replaced that bent box cover.

One more question... How did you secure your box? I am using a nylon rope attached to the cargo net hooks. It works ok but I was wondering if there is a better solution.


08-28-2007, 10:27 PM
ummm.... i dont really have problem with the dsp or maybe i dont notice it. idk. but i have the bass boost knob installed under my steering wheel so i can control it from there. i dont have any rattle either inside the car. i heard the only solution is to dynamite the whole trunk. anyway my box is not secured at all. i just slid the box all the way back and put two strips of the sharp half of velcro to the bottom of the box and it sticks to the carpet. the main thing that holds the box in place is the floor board you see in the picture. it keeps the box from sliding forward. pretty much it