A:Answer The yellow tipped cable for a Composite or RCA cable has nothing to do with audio. The yellow cable carries the video signal. The Red and White tipped cables are what carry the Stereo Analog Audio signal. Current TVs do not have an RCA Audio Output that you can use to connect to a mini shelf system like the LG 700W 2.1ch Mini Shelf System with Built-in Subwoofer and Bluetooth®, Model # CM4550 which has an AUX Input. The LG 4K UHD HDR Smart LED TV - 55" Class (54.6" Diag), Model # 55UJ6300 only has an Optical Digital Audio Output as the only Audio Output on it so it would not have worked with the CM4550 which is why you didn't get any audio. You basically connected an input to another input. The only way that you could have connected the TV's Optical Digital Audio Output to the AUX In on the CM4550 would have been to purchase a Digital/Analog Converter. One end of the converter has an Optical Digital Audio Input that you can connect to the TV's Optical Digital Audio Output with an optical (Toslink) cable and the other end has the RCA Stereo Analog Audio Output (Red/White) that you can connect to the AUX In on the CM4550 using an RCA Stereo Audio Cable. If your Best Buy store does not carry the Digital/Analog Converter, you can find it on Best Buy online...^IFV