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Changing out 8?ohm for a 4ohm...

I've got an old pair of 3 way speakers (Avance Epsilon 980) rated at 4ohms and 89db sensitivity. (4) 7" ScanSpeak drivers #8544-09. Now, I thought the number designation on ScanSpeaks means that '8' stands for 8ohms. If so, how can they be 4ohm speakers? But my real question is: I have a chance to pick up 2 new ScanSpeak Revelators that I know are 4ohms, for a really good price. So, can I trade out just the mid woofers in these for the Revelators without screwing anything up, specifically the Revelators? Also Revelators are 92db. Bad idea? Feasible?

Amp can handle 4ohm loads no problem.

thecarpathian

Showing 2 responses by viridian

viridian's avatar
viridian
5,298 posts
 

The formula for determining the impedance of any speaker with parallel drivers is: 1 / (1/Z1 + 1/Z2 + ... + 1/Zn), where Z1, Z2, etc. are the impedances of the individual drivers. 

viridian's avatar
viridian
5,298 posts
 

Yes, you can, but it is rather approximate. Use your meter on the resistance scale (ohms), but understand that impedance is not resistance and the impedance will generally be noticeably higher than the resistance measurement.

Sorry that math is complicated, but if using two drivers with with the same impedances, just divide by two. So two 8 ohm drivers in parallel will have a net impedance of 4 ohms, and two 4 ohm drivers in parallel will have a net impedance of 2 ohms. Hope that helps.

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