View Full Version : Sub amp wired to bmw factory head unit.
09-20-2011, 01:27 PM
I'm fairly familiar with how to install stereo equipment, however I do not know if it's possible or how to install a subwoofer and amp to a factory bmw head unit. How easy is this? I would most likely be installing 2 10" subs with a 500 watt amp. I like the look of the stock head unit in the bmw, so I don't want to change it. I'm pretty sure it can be done, I'm just not sure how to do it, so if anyone could inform me that would be great.
09-20-2011, 02:36 PM
I'm fairly familiar with how to install stereo equipment, however I do not know if it's possible or how to install a subwoofer and amp to a factory bmw head unit.
How easy is this?
Very. BMW's, IMO, are some of the easiest cars to work on. Everything comes apart and goes back together easily and the battery is in the back. Doesn't get much easier than that.
I would most likely be installing 2 10" subs with a 500 watt amp. I like the look of the stock head unit in the bmw, so I don't want to change it. I'm pretty sure it can be done, I'm just not sure how to do it, so if anyone could inform me that would be great.
Find your factory BMW amp. If you look at the wire harness going into it you'll notice a series of wires that are twisted; those are the amp's input. You'll also notice a white wire; that's the remote turn-on.
What you have to do from there is use the amp's high level inputs (usually a separate small harness) and tap into the amp's inputs. Positive/Negative should be easy to find out as each set of twisted wires will either have 1 wire darker than the other or 1 wire with a stripe on it. I forgot which. To figure out left and right, front & rear, use the fade control on the HU and test for voltage.
Use Scotch Locks (available at a hardware store) and some primary.
Another neat thing about having the battery in the back is you can get away with smaller power wire. So an amp that normally requires 4ga can now use 8ga b/c the run is much shorter. That'll save you a few bucks so you can buy a better amp.
BTW; what kind of amp are you looking to purchase? I'd also see if you can find a 2nd hand JL Stealthbox for your BMW (I'm assuming you have an older 3-Series) or think about a pair of 8" free-air woofers. BMWs are difficult to get a lot of bass in them and the difference between a pair of free-air 8's and a pair of sealed 10's won't be much. If anything, the 8's will probably be a little louder and play deeper.
09-21-2011, 10:36 AM
Well, here's my deal on this... Does your factory hu have a sub out already? Because I know that at least with my tribute it came with a stock amp/sub but it was standard speaker wire, If this is the case, then i would just get a loc and wire it into the pre-existing sub channel.
Scosche LOC80 2-channel line output converter at Crutchfield.com (http://www.crutchfield.com/p_142LOC80/Scosche-LOC80.html?search=loc)
Hope this helps!