You can only connect speakers here that are equipped with a power amplifier. Speakers that have a power amplifier can be recognized by the fact that they have a volume unit themselves, so you can adjust the volume of the speaker on the speaker itself. If you connect these speakers to the radio, you can only control the sound from the radio speakers via the radio. So you adjust the volume level of the speakers via the speakers themselves. So you cannot adjust the sound level of all speakers in one go.