How do I adjust the volume for speakers themselves?

I have 5 speakers hooked up to 2 1/4 stereo plugs and those two plugs are connected to a Y adapter, which is then going into my laptop/ipod. It seems like my ipod and laptop don't supply enough volume for the speakers to be worth setting up. Is there any manual adapter or other way I can manually adjust the volume of the speakers with aid to the volume control of my ipod and laptop?How do I adjust the volume for speakers themselves?Your laptop or your ipod don't have enough power to work with all those speakers. You need to get an amplifier with its own power supply. An amp usually has its own volume control too.