Polestar Audio


HK Amplifer Teardown

Block Diagram

Upgrading Audio

Introduction Adding a Power Cable Centre speaker Front A pillar tweeter Front door speaker Rear door speakers Surround speakers Adding a subwoofer Adding a DSP / amplifer Schematic of my system

Wiring info

Speaker Wiring Colours


CANBUS Overview CANBUS Codes Module Location and info

☰ Menu Polestar2

This upgrade sections covers the following:-

Please note that any items that I have used in this install are items that I selected for my own personal preference. Do check that they fit your needs before purchasing anything.


The connection methodology of adding a DSP to the output of the factory fit amplifier is not ideal. In an ideal world you would connect direct to the audio source from the head unit and thus provided the cleanest source material possible. In the Polestar2 this is not possible (yet) as the connectivity is done via a digital optical signal. Existing MOST solutions like the Valse MOST150 and Audison DIT-DMI reportedly don't work in the Polestar due to Polestar security implementations. I have read that if you can get Polestar to disable their security settings then these items may work, however they are reluctant or typically refuse to do it. In the mean time I will continue to use the analogue output from the factory amp and try and reverse engineer the amplifier to get to the pre-DSP'd I2S signal.

Things to consider when using the output of the factory amplifier:-

Adding a larger Power Cable

Adding a larger power cable to supply an extra amplifier is essential.
The first thing to check was if the 12V battery could cope with the extra load. Given that EV's don't have an alternator that charge the 12V battery I tried to find a wiring diagram. For the polestar they just don't seem to be available. Living in the UK I don't have access to the VIDA support program. I eventually found a forum post that claimed 220A charging.

For my needs I installed a fused 4-gauge cable direct to the 12V battery. It is the yellow cable in the images below.
To do this start by removing the frunk. There are two bolts in the base of the frunk that need to be removed. After that the plastic surround can simply be removed. The plastic surround is held on with small clips, lift the centre pin and the clips are easily removed. Frunk removal only took about 5-10 minutes.

Once the frunk and surround have been removed you will see the 12V battery.

 ⚠  Don't touch or play with anything orange, it's 400V!
 ⚠  It goes without saying, run all of the cables before attaching the cable to the 12V battery.

The reason for sliding the battery forward is so that you can access a large rubber grommet that goes through the bulkhead.
Note that this grommet is double skinned, I had to use a draw wire to get the cable to go though both sides. Threading this cable through the bulkhead took me over an hour. Hopefully with these diagrams and pictures it should be easier for others to do.

I threaded the cable from the battery side through to the inside.
Note that my car is a right hand drive. The grommet is located behind the glove compartment. I had to remove the glove compartment to access the cable.
Once the cable is through the bulkhead it can simply be run up the side of the car by removing the side trim. There is plenty of room in the access channels.

You can see the inline fuse below. I cable-tied it to main loom for stability.

When you are happy that the cable has been routed and the exposed end terminated or insulated, the final connection to the battery can be made. I connected it securely to the location point shown below.

Speaker upgrades and sizes

Centre Speaker

The centre speaker is 10cm full range speaker. I didn't bother replacing this speaker I simply turned the gain down of this channel in the DSP. I do not favour a centre speaker featuring in my soundstage.
There are no off the shelf speakers available as a replacement. Although some of the BMW fitments are incredibly close.
The grill for the centre speaker is easy to remove, it simply unclips.

Front A pillar tweeter.

 ⚠  Caution. There is an airbag that is located behind this panel. Take care to treat it with the appropriate amount of caution.  ⚠ 

There are four stages to removing this panel:-

The frame that holds the tweeter to the pillar simply unclips.
Again caution is advised around the airbag ties, make a note of how the ties are threaded through the tweeter frame.
The tweeter itself can now be unclipped from frame. I drilled a small hole in the frame and attached a 25mm Helix driver to it

Frame with 25mm / 1" Helix S 1T fitted.

I packed a small amount of filler material under one side of the tweeter so that it tilted it towards the cabin and faced the correct direction.

 ⚠  Note that this tweeter does not have a high frequency crossover fitted as it is driven directly from a pre filtered channel on the amplifier.
      Either ensure that you use a channel on the amplifier that has been configured for high pass only or add a crossover.

Front Door midrange

There are 4 screws that secure the door panel.

The whole panel will now lift up. Do not lift it too far as you will need to remove the cable that is attached to the pull handle, also unclip the connector for the wiring loom.
Go careful with the pull handle clip, whilst I didn't break mine it was a little tough and feels a bit fragile.
Despite some forums saying that the centre speaker and the front midrange door speakers are the same, they aren't. The front door speaker has a different mounting frame.

I replaced this speaker with 10cm Helix S 4B in conjunction with InCarTec 40-1683-100 mounting rings. The speaker itself has some metal tabs that will need removing for it to fit.
The mounting ring needs to be placed behind the speaker to clamp it in place. This is not the way that the bracket was intended to be used, but it works with no modification!

Again no crossovers were used here as the output is filtered at the amplifier.

Rear door midrange and tweeter

The rear door panel removal is the same as the front door.
All of the rear door speakers are part of the Helix S 62C.2 2-way component set.

The tweeter is mounted on the door panel, the midrange driver is mounted to the door itself.
Both of these speakers are driven from a single amplifier channel and a crossover is required.



I have again used the 25mm Helix S 1T tweeter. This fits perfectly in the place of the removed factory one. I fashioned a small brace to hold it in place using the original mounting posts.
This time a crossover is required and mounts nicely on the back of the brace. There is sufficient clearance that it does not foul the door when it is refitted.


For this I have used the 16.5cm Helix S 6B speaker.
Adapter rings InCarTec 40-1793W-165 were bought however the footprint of these is not correct and is not suitable for direct use.
The construction of the adapter rings are actually in two parts. A 16.5cm ring and then the adapter frame. I split the adapters and just used the top 16.5cm ring.

This ring was screwed directly into the basket of the door, with a small hole added at the bottom for the speaker cable to exit.
The speaker itself was then attached to that ring.

You can see in the image above that there is a small amount of room above the speaker to mount the crossover.
When replacing all of the door speakers take the time to add sound deadening / anti vibration material to the door skins etc.

Surround Speakers

To access these parcel shelf speakers the surrounding trim simply unclips.
As the replacement for these I used the HELIX S 3M 75 mm / 3" cone midrange speakers.
To mount these I trashed the original speaker and removed the cone and driver. A small amount of the circular frame was cut back and then the new speaker was screwed into that original frame.


Front Air woofer and Subwoofer

I did not upgrade these. I have used the front air-woofer as a bit of front low volume, low range fill, but it is not doing any heavy work.
This is a dual coil speaker that is driven off of two low passed amplifier channels.

The rear subwoofer has been turned off in favour of my subwoofer.

Additional Subwoofer

The subwoofer design section is not intended to be a full lesson on box design, that really is an art in itself. This is a high level overview of the design practices that I used.

This consists of a Focal FPX 2.750 amplifier and a JL Audio 12TW3-D4 subwoofer.

My initial subwoofer design just didn't perform to my expectations. This design was a sealed enclosure that would fit in the liner of the boot tray.
It's rear capacity was limited to about 18 litres and simply was not good enough. While the quality was OK the SPL and low end response was very poor.

My final design is a 33 litre ported enclosure that uses the boot floor itself as part of the enclosure.
You can see from the design below that there is a huge benefit in using the ported design over the sealed enclosure.

The achievable gross rear enclosure volume was calculated to be 33 litres. A port tuning frequency of 32Hz was selected with a 6 x 14cm port of 66cm long. These mostly match the JL recommended ported enclosure parameters
To achieve the 66cm port length a slight curve was required, this helps it fit within the base of the enclosure and make the port exit from the top of the speaker. As long as tight right angles and air disturbance are avoided this is OK. Worst case air speed was calculated to be about 24m/s, this is higher than the target 17m/s but it occurs in an area when the overall system peaks are reducing.

Note that Net rear speaker volume is Gross rear volume (33L) - Speaker displacement (0.82L) - Port displacement (5.83L) = 26.34L

After creating a cardboard template of the boot shelf, a frame was made out of MDF and bonded to the boot floor. A liberal covering of sound deadening material was used to stiffen the floor and create an airtight enclosure.
The port design and construction needs to be accurate or you will suffer from poor frequency response, distortions or port farts.

Showing the MDF frame and the sound proofing.

Added Carpet and showing the tuning port.

DSP / amplifier

There is no physical remote turn on wire available for the amplifier so I rely on the auto-remote function. This seems to work well. The remote out pin of the Helix DSP controls the remote on/off of the Focal amplifier.
The focal amplifier is driven from the phono output from the Helix DSP

The factory speaker wires were cut and wired directly into the amplifier.

Point of note, I'm not creating a 'show car', this install is functional and for 99% of the time all of this is hidden under the boot floor.
I could make a nice carpeted cover to go over all of the wires and add some fancy LED's. Who knows that may get done at a later date.

The speaker out connector of the factory HK amplifier was soldered to extension wires, these go into the inputs of the Helix DSP.
All 12 of the factory HK amplifier channels are fed into the Helix unit.

The cables do not really need to be quite this thick, the input to the DSP is higher impedance than a speaker so there is less current flow.

 ⚠  When using the Helix DSP you will need to configure the input gain correctly.
Refer to the Helix manual for how to configure the input sensitivity.
From my understanding the HK outputs are ~28W into 4ohm, this puts it in the High Voltage Range
If you do not change the configuration you may get clipping at high volume.

In the Helix manual it refers to connections to class SB amplifiers. One of the IC's within the HK amplifier is of this type. However I have not noticed any issues with this as yet and I have not had to enable it.

Basic input and output mapping could look like this:-

The outputs can be arbitrarily wired. You should try to group the inputs as it will allow for more flexible control over the main input sensitivity gain (This is done in pairs)

I'm not going to cover DSP configuration as it is really down to a matter of personal taste.
A few words of caution though:-

I've not yet purchased a calibrated microphone however I did have an Audyssey microphone to hand that I used for my initial setting up.

Final Equipment list