Hi I am new to this forum and this question might not be in the right place. I am mounting an amplifier and extension speaker on a metal detector which normally uses headphones. The speaker is small diameter about 2inches wide. It is only 0.5 watt by 4 ohm. would a 5watt by 8 ohm speaker use more power. I am only getting 3hrs usage before the battery is flat in its present set up and dont want to reduce its time any further. Thanks Nello