Speaker Resistance

Steel guitar amplifiers, effects, etc.

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Skip Ellis
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Speaker Resistance

Post by Skip Ellis »

Approximately what dc resistance should I read when measuring an 8 ohm speaker? I've got a 15" out of an old Polytone bass amp that I thought about putting in a cabinet and using for an external speaker for my Roland Cube 60 which calls for 8 ohm. I thought the 15 might make the amp a little more suitable for steel.
Thanks!!
2013 Brook Torridge, 2014 Martin 000-18, two homebrew Teles, Evans RE200 amp, Quilter 101R head, understanding wife of 45 years. 'Steeless' at the moment but looking......
Ray McCarthy
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Post by Ray McCarthy »

I don't believe you can determine the impedance of a speaker by measuring the DC resistance--the impedance would be determined by several factors, including the magnet's properties. If it is a 4-ohm speaker, It will allow the amp to produce a little more power, but it should work OK.
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Skip Ellis
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Post by Skip Ellis »

Thanks, guys!
2013 Brook Torridge, 2014 Martin 000-18, two homebrew Teles, Evans RE200 amp, Quilter 101R head, understanding wife of 45 years. 'Steeless' at the moment but looking......
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Greg Cutshaw
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Post by Greg Cutshaw »

You can see from this chart that the rated impedance of a speaker is 20% higher than the speaker's measured DC resistance.


Image


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Gary Jones
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Post by Gary Jones »

The general rule of thumb is to measure the DC resistance of a speaker (with nothing else attached) and multiply that by 1.3, so an 8 Ohm speaker should measure around 6.15 Ohm dc.
Of course this is only a ballpark figure, but since musical instrument speakers usually only come in 4, 8, or 16 Ohm varieties, that measurement should be enough to tell them apart.

Here is a good article on speaker impedances. http://www.epanorama.net/documents/audi ... dance.html


Gary Jones
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