R53 HK audio system architecture
 

I have a 2005 MCS with the full JCW package (engine, suspension, aero kit) and the HK sound system in it. The sound system works fine and sounds at least acceptable. I am considering some upgrades though in search of better iPhone support and SiriusXM capability. The information I need so that I can plan things is:

1. How is the head unit wired to the amp in the right rear, what sort of connectors? Line level or speaker level?
2. Where is the crossover for the front door speakers (woofer/tweeter)?

I couldn't find this info by searching the forum, thanks in advance for any info you can provide.

The HU drives the amp with high-level (not really speaker-level) audio over two twisted pairs. In a typical head-only upgrade, these can be fed with speaker-level signals without hurting the HK box.

Crossover and signal conditioning for the front speakers is handled in the preamp stage inside the HK unit; each of the front speakers have their own amplifier channel.

There is a massive amount of information here, although difficult to search for. You can start in the sticky threads:
https://www.northamericanmotoring.co...-upgrades.html
https://www.northamericanmotoring.co...nd-system.html

The head unit drives the HK amp with high level audio signals, but there are separate control signals for volume, balance, fading, etc on a digital bus between the HU and amp.

Have you seen the Grom unit to do this?

Also, do you have the sound settings on h/k mode? This uses the rear speakers as subs and produces very clean sound. You will spend LOTS of money getting a new system to sound better than the h/k amp & speakers on that setting. You CAN upgrade the head unit and still use the h/k amp & spekaers if you buy the hk enabler.