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X3 F25 (2011 - 2017)
The second generation X3 added style and new features to the BMW's mid-sized SUV. Talk about the BMW F25 X3 with other X3 owners now!

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Old 11-04-2012, 01:45 PM
Vortec4800 Vortec4800 is offline
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Location: Dallas, TX
Join Date: Jun 2006
Posts: 419
Mein Auto: 13 X3 35i MSport, 09 135i
X3 Stereo Upgrade Build

In my past several vehicles I've always done stereo upgrades, and I knew the X3 would be no different. I specifically ordered my X3 with the most basic stereo possible for this reason, and planned out something pretty nice.

Here is the equipment list:

Jehnert 3-Way Flat-Line Speaker Kit (Front)
Jehnert 2-Way Flat-Line Speaker Kit (Rear)
Mosconi AS 100.4 4 Channel Amplifier
Mosconi One 120.2 2 Channel Amplifier
Mosconi 6to8 DSP

The 3-Way kit is for the fronts; 2 speakers in the doors and an 8" driver under each seat. The 2-Way kit is identical to the fronts but without the 8" speakers. The AS 4 channel amp will be used to power the fronts, 2 channels for the doors and 2 channels for the 8" drivers. The other 2 channel amp will be used to power the rears. For the moment, there is no subwoofer in the system - the idea is the two 8" speakers will take on subwoofer duty. We'll see how that goes, we built it in a way that I can add a subwoofer to the system pretty easily if I want it in the future. The DSP will handle EQ duty and everything is connected directly to the low-level outputs from the factory source unit using a plug-and-play harness built by a fellow forum member. Battery in the trunk means no wiring has to be run at all from the trunk anywhere else in the vehicle.

Before I show the photos, a quick thank you to Jacob Brown of High Desert Mobile Electronics for making this possible. He helped plan everything out and then ended up doing the install. Everything went perfectly and - as always - I couldn't be happier with it all.

Without further adieu, here are a few choice photos from the install, with the entire album available at my Flickr album:


These are the front and rear door speakers, both the tweeters and mids.

These are the under-seat 8" speakers, which are very thin (the magnet is inverted so they fit in the OEM enclosure).

Here is Jacob working on removing the OEM under-seat speaker. These were actually the easiest speakers to install, they fit right in and were a piece of cake.

Comparison shot of the new under-seat speaker and the old. The OEM speaker was really weird, it was totally inverted, not just the magnet.

Comparison shot of the new mid-range and the OEM one.

Second comparison shot of the new and old mid-range speakers, here is where you can really see the difference.

Here's how we wired the door. In order to get the crossover to fit we had to disassemble it a bit and mount the PDB directly. The wiring swings around the bottom of the door and up to the speakers to connect to everything.

Here's the speaker mounted to the door. We added some felt to the underside of the mounting ring to ensure it has a good seal and doesn't rattle.

This is a shot of the OEM integration harness all wired up and ready to go. This gives us factory remote turn on for all the amps, speaker wires (which are nice, twisted pair wires) and balanced RCA outputs from the source unit. This made the install so easy.

Here is how we mounted all the equipment in the rear. I've never used any of these compartments so I didn't have a problem giving them up, and with the floor down everything is hidden. In this photo, the input RCAs are run as are all the speaker wires.

Here we are with all the power finished along with the remainder of the RCA cables.

First boot-up and we're setting up the DSP using the laptop. The DSP has bluetooth so all adjustments are made wirelessly.

Here's what it looks like all finished, right before the floor goes back in. Everything mounted securely and wired cleanly.
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Old 11-04-2012, 10:05 PM
Evlengr's Avatar
Evlengr Evlengr is offline
Ukemi - that's how I roll
Location: MD
Join Date: Feb 2007
Posts: 4,252
Mein Auto: 2013 Audi S4 2010 MT MCS
Excellent layout and work. I have installed several stereo systems in the older X3's and advised even Crutchfield Electronics. I presume you kept the H/U in place and used an in line dsp.

Not familiar with the audio speakers used, but they look like some good gear. I actually used two amps. One a 5 in 1 and a two channel. This enabled me to use the 4 channels for the doors, the mono section for a 10" subwoofer and the other 2 channel amp for the 8 inch under the seat.

This allowed for a 3 way Xover.

I have noticed that BMW puts the worst sound systems possible in the X3. Dont know why, but they do.

Great work.....
2013 S4 Loaded (and NO RFT's) Awesome is an understatement
2008 MT X3 RIP you were a faithful sidekick and will be missed.
2007 AT X3 RIPOS
2005 GC
2000 Jeep Cherokee
1997 Twin Turbo RX-7
1984 GTI Wolfsburg Edition Neuspeed and more
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