@robotmaker, I am in the process of moving into my condo, all project all temporarily cease. The only downfall of my project was waiting for part to come from China, I can share your pain.

@Technopro just do a quick search on Ebay for LM2596 or voltage regulator and choose the one that fit your need. They are less than $5 including shipping. I also use this one since it display the output voltage. most of them are like your h-bridge motor controller, can be solder or come with a cable.

Awesome solid information from Rich, PJ Robot-doc Lumpy and robotmaker! that info certainly helps me. thanks so much guys!

As @Rich mention, you can always design your own, more fun and you learn more by troubleshooting trough your errors. But at the same time, they are so cheap.

Found this regulator. it will regulate 5v down to 3.5v which is close enough. www.ebay.ca/itm/5pcs-LM2596-1-23V-30V-DC-DC-Buck-Converter-Step-Down-Module-Power-Supply-/121106457242?pt=LH_DefaultDomain_0&hash=item1c3281e29a

You can manually adjust it to fit what ever voltage you desire. Yes this will do.

Where are you getting your 5V from? If you take it from the EZ-B make sure you don't cause brownouts. Any idea on the power usage of the speaker?

Also, a further thought, if it is charged via USB you can just modify a USB cable and power from 5V since USB is 5V. It may be worth looking at that method (like DJ's method for the camera)

I don't do that anymore. it kept causing my ez-b to overheat, if you remember. I would like to wire the speaker up this way.

Edit: Big correction, the speaker has a 3.7v 450mah battery.

it's a delicate speaker so I need to wire it up to the correct voltage. if I use the regulator I found, it wont cause the ez-b to overheat, right?(in theory)

The EZ-B shouldn't overheat with any accessories attached unless there is a problem with the accessory itself. I suspect previously when your camera was causing the EZ-B to overheat that there was a short somewhere. Many others, including DJ have had no problems with that method.

LiPo batteries come in 3.7v denominations. But fully charged are 4.2v. 3.7v when you should charge. Under 3.0v and it's ruined. Under 3.5v and it's being damaged. So with that in mind you can use anything from 3.3v to 4.2v without it being a problem. 3.7v is ideal though, 4.2v wont kill it. You could get lucky and try a 5v supply but it's at your own risk.

If you use a regulator I would advise connecting it to the battery not the EZ-B. No chance of it doing anything to the EZ-B in that case.