Square dance audio on the 4558 is an operational amplifier, can amplify the audio current, audio on the two 4558 because of the audio volume to amplify or reduce the adjustment.
Speaker refers to the audio signal can be transformed into a sound device. In layman's terms, it means that the speaker host box or subwoofer box with its own power amplifier, the audio signal amplification process by the speaker itself back to play back the sound, so that the sound becomes bigger.