I don't manage to output the audio from my projector Mitsubishi HC4000 to my harman speakers, with a RCA to 3.5 jack adaptor.
I've connected the adaptor to the blue and red RCA output in the picture and to the speakers jack. Also, I've connected an Apple TV to the projector with HDMI cable.
I've also tried to increase the speakers volume (very loud), but I can't even listen to the "soft" signal (I've checked this because I was afraid I needed an amplifier. Even without amplifier the audio signal should be slightly perceptible, but I can't really hear any difference).