How to Upgrade the E9X E90 E91 E92 E93 HiFi Sound System (option 676)

The HiFi Sound System (Option 676) is composed of the following:

6 channels
10 loudspeakers
• 2 treble loudspeakers, front 26 mm
• 2 mid-range loudspeakers, front 100 mm
• 2 bass loudspeakers, 217 mm
• 2 mid-range loudspeakers, rear, 100 mm
• 2 treble loudspeakers, rear 26 mm
Bandwidth: 40 Hz to 20.000 Hz
Max. acoustic pressure: 104 dB

Amplifier power:
2 Under seat Sub-woofers x 40 W (2 Ω) Bass
4 Speakers x 25 W (2 Ω)

Supplies Needed:

• 2 x Helix Match MS 42C Universal 4" Component Speaker System
• 4 x Four point to 3 point speaker mount
• (Optional) 4 x BMW Speaker Connectors if you don't want to cut the wiring
• (Optional) 1 x Foam Tape & 1 x Sound Deadening if you want less vibration
• 5 or 6 channel AMP
• 4 Gauge or Larger AMP wiring kit.
• Wire Strippers or similar
• (Optional) Wire Ferrules if you want a cleaner install

Total Cost: A little over $700

Step 1. Speakers

The OEM Speakers are 25 W @ 2 OHM’s (Ω) .

The Helix Match MS42C are 35 W @ 4 OHM's (Ω) .

NOTES:

1. This means we'll need a bit more power or to turn up the volume quite a bit.
2. For Example if I had used a 50 W @ 4 OHM's (Ω) I would need double the volume on the stock amp.
3. These are not BMW specific so some retrofitting will be needed.
4. Speakers that use more power than amp can put out can damage the speakers (clipping).
5. It is better to overpower the speakers and be conservative with the volume than under-power and try to do the same.

Link: https://www.amazon.com/gp/product/B00PCLVNJO/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

To

Step 2. Replacing the Stock HiFi Amp

NOTE: High level inputs means that you are using the speaker wire leads off of the back of the radio instead of using the RCA connections. Making RCA connections from the speaker wire leads on the back of the radio does not change the fact.

1. Get a "BMW E90/F10/F20/F30 Hi Fi AMP Connector Harness", as I would highly recommend not cutting up the wiring harness here.
• Link: https://ebay.us/jSo3ZV  (or similar)
2. I used a "Pioneer GM-D9705 AMP" with the High Level Input (Speaker level) and the one sub channel. 
3. Since this is a 5 Channel amp you will need to combine the 4 sub-woofer inputs into 2 inputs because there is only one sub channel. This will create a higher 4 OHM rating.
4. I used another 100A fuse with 4 gauge wire between the positive battery terminal and the amp.

AMP Wire Harness from eBay

High Level (Speaker Level) Input Instructions from Pioneer GM-D9705 Manual

You will need to cut the 4 RCA's on the Harness above to attach here.

How to wire the 2 under-seat sub-woofer into one channel

The Power Wire with a 100A AGU Fuse

Full Diagram

Stock Speaker and Sub Specs if you didn't upgrade some stuff

Step 3. Tuning  (Done but not satisfied....In Progress)

1. I used the high level (“speaker level”) wiring harness provided which connects to the speaker wiring from the radio directly into the amp. 
2. To tune you will need to go through a variety of test tones (40, 100, 400, 800, and 1000 Hz) at either 75% or the max volume you will need. Then backing off when you see clipping or hear buzzing.
3. To get 75% volume or close to any reading you will need to get a volume meter out of the stock HiFi radio. Here is a quote from the 1-series thread, also found on an E90post:
1.  turn on the radio
2. press button "m" or "tp" for at least 8 sec.
3. "+" and "-" to navigate through the menu (there must be a submenu "volume" or something like that, then use the volume-knob to see how high the level goes)
4. turn off radio and on again
4. I have the gain set to 50% on the "Pioneer GM-D9705 AMP" to provide a clipping, buzz free, and alternator whine free experience. I'm still not 100% satisfied as I could like a little less bass but overall it turned out great.

Step 4. After Market Radio (Future Project)

NOTE:

1. The Stock HiFi Radio is codded to have a flat EQ apparently.
2. A double din aftermarket radio would require a relocation of the heated seat buttons. 
3. Although the EQ is flat it is still a High Level Output. "Most" amps like to take Low Level Output.
4. If you need to convert the High Level to Low Level just use a LOC (Line Output Converter)