Speaker Impedance - Novice

thisoldhaunt
thisoldhaunt Posts: 1
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
Post edited by thisoldhaunt on

Comments

  • mhardy6647
    mhardy6647 Posts: 33,954
    edited December 2007
    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
    treitz3 Posts: 19,184
    edited December 2007
    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.
    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
  • mhardy6647
    mhardy6647 Posts: 33,954
    edited December 2007
    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
    rskarvan Posts: 2,374
    edited December 2007
    Solution: Get an amplifier that supports a 4 ohm speaker load.
  • phipiper10
    phipiper10 Posts: 955
    edited December 2007
    ^^ what he said.
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  • wingnut4772
    wingnut4772 Posts: 7,519
    edited December 2007
    What he said that he said.
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  • zingo
    zingo Posts: 11,258
    edited December 2007
    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
    mrbigbluelight Posts: 9,830
    edited December 2007
    What he said that she said that he said that he said.
    Sal Palooza
  • daboyz
    daboyz Posts: 5,207
    edited December 2007
  • Odd I/O
    Odd I/O Posts: 13
    edited December 2007
    treitz3 wrote: »
    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?
    ...i'm a picker, i'm a grinner, i'm a lover, and i'm a sinner; I play my music in the Sun...
  • rskarvan
    rskarvan Posts: 2,374
    edited December 2007
    Odd I/O wrote: »
    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.