Batterys and Voltage Question
im planning on building a speaker rucksack, i.e modifing some speakers into a rucksack. now the speakers i have chosen to mod into the bag are mains powered but i want to power them with batteries.
The speaker adaptor looks like this...
and reads "Logic3 AC/DC ADAPTOR CLASS 2 TRANSFORMER, INPUT : 230V 50Hz, OUTPUT : 15V 1200mA MODEL : D57-15-1200"
I have 2 batteries which combined i think i could use to power the speakers, they look like this...
Small light coloured one reads "VALVE REGULATED RECHARGEABLE BATTERY, HGL3.2-6, 6V3.2Ah/20HR, CYCLIC.
Big dark coloured one reads "SEALED MAINTENANCE-FREE RECHARGEABLE BATTERY, UL3.4-12(12V,3.4AH/20HR).
As i understand it the speakers run off of 15V 1200mA and the batteries together will produce 18v. this is too much power for the speakers so i need something to step down the power to the right voltage for the speakers.
what do i need to do this? a certain component, resistor maybe?
any help would be greatly appreciated, thanks :)