USB and 5V feed (resolved)

[jackpilot]

I have a set of amplified  PC speakers dedicated to P3D ATC
input is a 3mm jack (OK)
power is a USB plug (not OK)

As I intend to locate them in the ceiling the USB power feed is impractical and I would like to substitute direct 5V from the OVH 5v bus.
If I cut the wire, i should find 2 wires, if yes how to make sure of the + and -
Any idea or better idea ?

[XOrionFE]

why not just plug in the end you cut off into usb jack and measure for voltage on the wires from the multimeter using a separate ground?

[jackpilot]

Separate ground ?

Actually the USB wire is really thin (1mm) and I m not sure to be able to identify the two wires supposedly in it

And if I try blind I have 50% chance to be right and 50% to blow it, right? 

[Bob Reed]

Here is the pinout for a standard 2.0 USB port. Use a meter to determine which wire is witch.

https://theydiffer.com/difference-between-usb-2-0-and-3-0-cables/

[jackpilot]

Thanks Guys Good enough...I'll try 

[jackpilot]

I managed to acess the inside of one speaker box and used Bob's pinout to locate the wires
Turned out with the ohm meter white positive and red ground

Then Scott method cut out the USB, plugged it in, and check with the voltmeter, confirming white + and red -   (chinese code?)

Thank you guys

[Bob Reed]

I managed to acess the inside of one speaker box and used Bob's pinout to locate the wires
Turned out with the ohm meter white positive and red ground

Then Scott method cut out the USB, plugged it in, and check with the voltmeter, confirming white + and red -   (chinese code?)

Thank you guys

Glad we could help!