# Connect lower power speaker to audio amplifier

I want to test an audio amplifier based on TDA7294 and the highest rated speaker I have has 20W @ 4 ohms.

How can I connect it to the output of the amplifier without destroying it? I'm thinking I should use a series resistor, but how to calculate value and power?

I don't need a long term, reliable solution. I just want to test the amplifier at its maximum output power and I don't have the required speaker.

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What "test" do you want to do? If you want to verify its electrical performance, just use a 4-ohm, 100 W resistor as a dummy load, and forget about the speaker. –  Dave Tweed May 8 at 14:26
If you follow the advice of those here about using a resistive load, I would use a scope to look at the signal to be sure there is no distortion (which you would have heard using a speaker, although a scope would have been useful then too). –  tcrosley May 8 at 16:23

You don't need a speaker at all. Get a 4 Ω power resistor, or parallel a bunch of higher resistance resistors to get the equivalent of 4 Ω at the required power handling capability. For example, twentyfive 100 Ω resistor in parallel will give you 4 Ω at 25 times the power rating of the individual resistors.

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You could use a resistor instead of the speaker, but it's not really exactly the same thing electrically.

Although the datasheet test circuit shows a speaker, the performance ise specified with a $R_L$ of 8$\Omega$.

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