A guide to upgrading the sound system on A3 8v (so that it's Hi-Fi and better than the B&O system) | Audi-Sport.net
Audi A3 FWD Underfloor Sub Box (2006-2013)
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For Audi A3 S3 Q2 2017-2019 Bo Horn Bo Speaker Audio Subwoofer Car Door Horn - Subwoofers - AliExpress
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M.A.P Audio & Customs - Custom made fiberglass 8" subwoofer enclosure for an audi a3 8v. This was hand made with mdf rings and support braces. It was then fiberglass and covered
Upgrading Audi A3 OEM Subwoofer with aftermarket 8" JBL woofer and DS18 Candy Amp in stock location. - YouTube
Sold 2017 Audi A3 Audi Subwoofer Speaker Unit 8V0-035-412-B,
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2016 AUDI A3 (8V) SEDAN - RADIO STEREO SUB SUBWOOFER TWEETER SPEAKER SET-10 | eBay
Wicked C.A.S. > Audi > AUDI A3 Magic Box 10 / 12 / 13 SUB BOX SUBWOOFER ENCLOSURE