The device can probably work at 5v but if not here is a URL to a nice dc to dc unit that will regulate 9 to 40vdc down to 3.3vdc

I was looking at this one.

lm3940

That's just the LDO, you'll need to make a circuit to use that one, personally I'd use a pre-made regulator over making one, you know it's going to work and generally the cost difference is minimal, throw in the time taken to make it and it probably works out better value to buy a pre-made one.

You'll save around $1 at most by building the circuit yourself, if it works right away. For me it's better value to by a DC-DC converter pre-made.

MOST regulator circuits only take a few parts 2 caps and regulator chip

Plus they work at very low drop out better then most dc-dc converters some will as low as 3.4 volts with 3.3 volts out. What is means is that you battery will last much longer.

Look at the 3 pin 3.3 volt LDO that EZB uses super simple only 3 pins ,input,output and ground ,cant get more easy then that.

Some at a 4th pin for shutdown if it does just ground it.

The dropout looks fairly good on that one at .5 volts at 1amp and your circuit will use may be less. PLUS should only need one cap at the output ,since the 5 volt regulator has one. Spec sheet tells how easy to wire it up and pinout.

Another item about using it very tiny size compare to DC-DC CONVERTERS

I'd tap into the 3.3v right on he EZ-B if it doesn't draw to much amp.

The 3v3 on the EZ-B doesn't supply much at all, it doesn't provide enough to power the WiFi module I got for the EZ-B. But yes, try that first, it wont do any harm to throw a jumper from the 3v3 pin to the speaker.

I agree with RICH the 3.3 volts on board doesn't supply enough current for EZB and bluetooth ,plus it will get the regulator much more hotter then it is.

i THINK the bluetooth speaker draws at least 500 ma if not more.