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Old Sun, Apr-14-2019, 08:41:02 PM   #1
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Default Xtrons 7846BP Review (E46 M3)

This is my medium-term review of the Xtrons 7846BP for the E46 platform. I say that since I’ve had installed since December 2018.

I had initially had a Dynavin D99 head unit installed. I upgraded for the following reasons:

• Gain Google Maps in the dash for improved navi experience.
• Additional music, ‘search across device’ history and services via the Android ecosystem (Google Play, VLC, YouTube, etc.).
• Use of Harry’s Lap Timer in dash (to avoid having to tether my phone and its power connection).
• Re-gain the ability to play CD’s in addition to a better file browsing GUI experience when using USB sticks and SD cards.

My setup is fairly straightforward and is as follows:

• Head unit is feeding a MiniDSP C-DSP 6x8 processor with a Wifi adapter controlled by a Macbook Pro. This processor feeds an Alpine PDX-5 which feeds a Morel two-way component set and a pair of 6.5” Sundown subwoofers in a small removable enclosure I built in the trunk.
• A TPMS [05] unit is installed in-dash with internally mounted wheel sensors installed on 18” Apex FL-5’s.
• External, wired microphone installed in the OEM overhead space near the sunroof button.
• No rear view camera, no OBD connector or reversing camera, no 3G or 4G dongle, DVB_T.

I plan to use my Sony Android phone’s hotspot feature when I need to go online in-car. Google Maps via offline maps works for addresses only, not POI names. When offline, it also won’t get any search history that you made while on other signed in devices.

I’ll keep this is short as possible to avoid writing a book here.


Mine was unique in that I was re-using some of the Fakra cable connections and the remainder were direct runs to my downstream electronics. The label on the head unit has the wrong colors for the majority of the harness wires. Have a multimeter to confirm everything. This may get all worked out if you go the plug and play route. I deviated from this given my car setup and found issues (e.g. the steering wheel control was unsuccessful).

IMPORTANT: If you are using RCA connections and encounter alternator noise and have the head unit grounded to the same point of your amplifier, in the trunk disconnect that ground connection and drill a hold into the dash frame to the left of the head unit and connect there instead. 95% of my noise was resolved in this way.

• This unit powers up from sleep very quickly. Less than two seconds…to the last source you used.
• Google Maps works great.
• The highest output levels are achieved when using the CD drive. This is where I want the most output for my needs.
• Harry’s Lap Timer accelerometer calibration will not finish when you start this function. But the timer function will work without issue. To test it, I created a ‘custom track’ using my neighborhood and it was measuring time without issue. Having a large display in the dash on the track should be a welcome this season (white numbers, black background). I have my season’s tracks already loaded and will try the first (Palmer) out at the end of this month.

• The unit will not re-acquire the current time via GPS or network 90% of the time. I will need to learn how to get root access for this unit to allow another app to force time correction. The workaround is to go into Settings and toggle the GPS time selection, then it corrects. Otherwise when you turn the car off, time ‘stops’: if you come back 10min later, the time is 10min behind.
• Google Play will crash more often that on my Sony phone. It’s rare though.
• The display is near invisible in direct light.
• I haven’t been able to get TPMS to finish calibration. I noticed the thread about the Avant 4 had issues with this function as well. I will keep trying, but no pressure or temp measurements are possible when my track wheels are on the car. If I make progress on this, I’ll follow-up.

• Get into the factory menu to maximize the head unit output (to 0dB). It’s set at -12dB be default. I still think I need to get an Audio Control Overdrive Plus to give me more output so I can further reduce my amplifier gains.
• While you're there, adjust the sound mixing for maps versus the music output so that when she gives you direction, your music still plays, but temporarily at a lower level.

I haven't used the unit to handle calls from my Sony phone yet so I can’t comment on the microphone quality. I did take it apart and hot glue the transducer to the microphone panel for the best access to the cabin sound. It just required a small flathead driver to take it apart.

Let me know if you have any questions. I wanted to share my high level experience so others can make an informed decision regarding all of these units. Hope it’s useful.
Dakar Yellow E46 M3: TC Kline coilovers | Bimmerworld Delrin front/Turner Monoball rear arm bushings | Turner Aluminum Subframe Bushings + Reinforce | 3.91 M Diff | Fabspeed Headers & Cats + Status Gruppe Section 2 | Lots of maintenance
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Discussing Xtrons 7846BP Review (E46 M3) in the Audio/In Car Entertainment (I.C.E.) Forum - Place to discuss sights and sounds. at BMW M3 (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)