Speaker Impedance - Novice

[thisoldhaunt]

Hi,

I was hoping someone here could help me out. I want to use 4 ohm speakers for an amplifier that calls for 8 ohms speakers. Over heating is a serious concern.

Is there a way to modify a 4 ohm speaker so that it is 8 Ohms without drastically changing the sound quality of the speaker.

Thanks

Thisoldhaunt

[mhardy6647]

No. If you have two identical pairs, you can connect two speakers in series to each channel ( amp + to speaker 1 +, speaker 1 - to speaker 2 +, and speaker 2 - to amp -) to present an 8-ohm load to the amp.

[treitz3]

Yes. Get an autoformer. However, it may be cost-prohibitive to do so and might be cheaper just to replace the amp depending on what level you are starting at.

[mhardy6647]

oops, yup, you're right: an autoformer would do it. So would/could a pair of 70 volt PA transformers (4 ohm to 70 V on T1 to T2's 70 V to 8 ohm). A good autoformer will be costly, and the line transformers are not expensive pretty limited in bandwidth.

[rskarvan]

Solution: Get an amplifier that supports a 4 ohm speaker load.

[phipiper10]

^^ what he said.

[wingnut4772]

What he said that he said.

[zingo]

What he said the he said that... never mind.

What amp are you using thisoldhaunt? You can get some pretty cheap and decent amps that can easily do 4 ohms.

[mrbigbluelight]

What he said that she said that he said that he said.

[daboyz]

Whateverer

[Odd I/O]

Yes. Get an autoformer. However, it may be cost-prohibitive to do so and might be cheaper just to replace the amp depending on what level you are starting at.

I am wondering: Since the Autoformer is basically a silent dummy-load, could the same results be obtained by connecting a cheap 4 ohm speaker in series and placed somewhere in which it will not be heard (basement, attic etc?) ----Just for curiosity, is this idea equivalent to the Autoformer?

[rskarvan]

I am wondering: Since the Autoformer is basically a silent dummy-load, could the same results be obtained by connecting a cheap 4 ohm speaker in series and placed somewhere in which it will not be heard (basement, attic etc?) ----Just for curiosity, is this idea equivalent to the Autoformer?

I think the problem with approach would be that speakers aren't straight 4-ohm loads. Their impedance varies considerably with frequency. Therefore, 4+4 does not necessarily equal 8.

What is necessary is to have an amp capable of supplying the current that the speaker load demands (in an instantaneous moment in the song at a prescribed frequency). A 4-ohm speaker demands more current than an 8-ohm one. When the amp can't supply the required current, clipping results and can damage the speaker (typically, the tweeter).

That is why it is important to have an "adequate" amp for the speaker load. This is a superior approach to artificially increasing the impedance of the speaker to diminish the load on the amp.