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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
thecarpathian's avatar
thecarpathian OP
5,119 posts
 

They also have 3/4in tweeters which is not relevant to this conversation!

mulveling's avatar
mulveling
2,206 posts
 

Bad idea, though you could get lucky and have it work OK. Though it will no longer be the designer's intended performance. 

A single driver might be 8 ohms (or 4 ohms, etc) but once you put it into a network with other drivers and crossovers, and the net impedance often becomes something else. Usually the result is quite complex versus frequency, which is why speakers are rated at "nominal" impedance to make a nice single number.

If you had 8 ohm driver parts in a speaker rated 4 ohms nominal, and your replace them with 4 ohms driver parts, you'll usually be lowering the nominal impedance well below 4 ohms, possibly into the danger zone for your amp. 

thecarpathian's avatar
thecarpathian OP
5,119 posts
 

@mulveling ,

Thank you for the insight.

 

ckr1969
139 posts
 

if you change the drivers from 8 to 4 ohms you change the network frequency, you can't do that, it will sound awful

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