In the UK, BMW offered 3 audio levels in the 3 and 4 series platforms.

 

Base Audio - no amplifier, no tweeters, 4" in the front door, 6" under seat 'woofers', 4" in the rear door.

Hi-Fi - analogue fed amplifier in the boot, tweeters in the front doors with non branded grills, 4" in the front door, a centre speaker, 8" under seat woofers, 4" in the rear door.

Harmon Kardon - digitally fed more powerful amp, tweeters with branded grills, 4" in the front door, a centre speaker with tweeter, 8" under seat woofers, 4" in the rear door with tweeter, surround speakers.

 

While the Harman Kardon in these cars isn't 'bad' for a factory system, there is still a huge amount to be gained dynamically and tonally in adding a DSP amp, replacing the cheap factory speakers and adding a dedicated sub to give real sub bass.

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There are many upgrade options, which isn't helped by the fact the 3 OEM systems all have unique challenges and characteristics and where the upgrade route is slightly different for each audio version.

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Therefore in some instances, we have set a sound package for each OEM system. if in doubt, please feel free to give us a call.