JBL and Smart designers have collaborated on the creation of the system, which is designed to deliver "optimal sound" despite the compact interiors of the cars. The first cars are due to hit the roads later this year.
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One of the features of the new system is a removable subwoofer should more space be needed in the boot – something that's described as a "clever solution that is a perfect fit with the smart driving experience".
The Smart fortwo will have a six-channel DSP high-performance amp and eight speakers, with the centre speaker in the middle of the dashboard and two tweeters located to the left and right of the A pillar.
Low mid-range speakers are fitted on the bottom of the front doors, with the two surround speakers placed at head height. The Smart forfour will feature two extra pairs of high-frequency and low mid-range speakers and an eight-channel amp.
Michael Mauser, president of Harman's Lifestyle Division, said: "Drivers of the new Smart can look forward to a thrilling sound experience when they take their new car onto the roads."