The power specs will be shown on the compliance label on the speaker. If this is the right one, then you need 14v and 1a.
Devices are pretty forgiving about these things, and having more is better than being low. So a few volts higher is fine, and amps can be as high as you want. But low amps would mean no charging, and low volts can mean frying things. VERY high voltage can fry it, but slightly low can also.
I can stick a 15v 2a power supply in the mail to you if you want. Just not sure which size of plug the speaker has.