Transformer for Subwoofer

[Littlebilly91]

I am trying to make a class d subwoofer amplifier. I have a 10:1 transformer and would like to make a 3:1 transformer by pulling out some windings (not sure if this is a good idea or not, I don't expect it to be easy). I am using a 4 Ohm Speaker with a power rating of over 100W. I plan on running it at about 50W. I have some loose transformers lying around (pictured). Is there any way to find out/estimate the power rating? Whatever power it draws as a 10:1 should be less than what it draws as 3:1, right? (V is higher, R stays the same)


I am powering it with a 120V 60Hz Wall outlet.

[DF96]

If you are talking about a mains power transformer then my advice is don't do whatever you are thinking of doing. I know enough about mains power transformers not to mess about with them. Your question suggests to me that you have less experience than me.

Instead, tell us what you are trying to achieve (e.g. DC voltage out, current draw).

[Littlebilly91]

Suggestion noted. I need a DC voltage out that is capable of drawing a lot (4 amps) of current. That voltage will Vcc for my class D amplifier, so I figured it would need to be in the neighborhood of 20 or 30 volts to get sufficient volume from the speaker. I can get 13 now, and I am concerned that the transformers I have can't handle as much current as I need.

[DF96]

You could rewind the secondary. It needs more turns, but this will of course reduce the current handling capacity. Much better to buy the right transformer.