EPI M250 and EPI M180 Speakers and their ohm rating???

[redpackman 0]

OK, I admit, I"m no expert when it comes to crossover electronics.  But go to the Human Speaker page dealing with EPI speakers in the late 70's. 

https://www.humanspeakers.com/e/epimodels.htm#more

Both the EPI M180 and EPI M250 have identical crossover schematics. They both have identical speakers in that configuration if you look at the replacement speakers one can order there.   I have a M250 that I just picked up. Three of the four woofers in that M250 pair rate at 6 to 8 ohms. One rated at 4 ohms. If you will notice  in both the M180 and M250 both woofers are wired in parallel.  If you have two woofers in parallel and both are 6 to 8 ohms isn't your overall speaker ohm rating going to be somewhere between 3.5 and 4 ohms, roughly?  I know, the tweeters will affect the reading some too, but work with me.  The M250 is rated at 4 ohms in the spec sheet which makes total sense to me with two 8 ohm speakers wired in parallel, but the M180 is rated at 8 ohms.  And that's from the same schematic with the same speakers. 

How can that be? 

Furthermore, I'm finding a lot of EPI 8" woofers test out at around 4 ohms all by themselves. Put them into a parallel wiring configuration like the M180/M250 schematic and what do you have? An ohm rating that's dangerously WAY below 4 ohms, isn't it?  And a lot of the EPI 8" woofers on eBay and elsewhere test out at 4 ohms not 8 ohms. I realize that a speaker's ohm rating is not static, but varies with the frequencies flowing through it, but aren't two 4 ohm woofers wired in parallel a real problem unless one's amp can handle ohm ratings down around 2 ohms?  I know, some say they can without being damaged  but.......

EPI must have made their 8"speakers in 8 ohm and 4 0hm varieties. Mixing them, particularly in parallel arrangements like this isn't going to work. 

[Woofer_01 0]

Here is a version of the EPI M180 that came with the Tweeter switch.

I rewired and recapped the crossover as shown, The schematic was a redraw of the original to match my updated wire labeling.