Computer speakers to Battery powered speakers...conversion problem need help

I recently converted a pair of old computer speakers to be powered by a 9v battery. basically i attached the 9v battery to the output end of the transformer..

HOWEVER

The output from the transformer is AC 8v / 250mA

Now the sound is different, for example vocals can't be heard as well where as lower tones can... How can i fix this... is it something to do with not enough power?

Any help would be really appreciated

You connected a DC only battery to the output of an AC transformer? Do you intend for the transformer to gently blow the music into the battery?

I hope you don't mean a 9v battery like they kind you put in a smoke detector. These are too small to run computer speaker amp. There is too much series resistance in these batteries for that application, not to mention you will run them to depletion in no time.

You can probably run the speakers on 9 vdc, of sufficient capacity, because the spkr/amp just has a bridge rectifier and filter cap to convert the 9vac transformer to DC to run the amp. You will lose about 1.3 vdc for the bridge rectifier forward voltage drop.