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Guido57

EPI M-110 Rebuild

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In the later 1970's one of the speakers I wanted to audition was the EPI 100.  Unfortunately, the salesman at the only place I could find them did not want to hook them up and tried shoveling so much bullshit on me in an effort to get me to buy their house brand I left and never went back.  These came up for free on the local Craig's List, obviously a fixer upper pair.  The previous owner still had the woofer for the mutilated cabinet so I decided to give it a go.  The butyl surrounds on the woofers have definitely stiffened and I decided to replace them with fillet foam surrounds that are still on their way.  A listening test to the complete speaker showed the degradation  from age and their storage in an unheated garage.   As a first step I put on new binding posts and replaced the crossover with the common EPI setup of a 10 uF capacitor parallel to the tweeter while adding a 1.5 ohm resister.  This brought the tweeter back nicely.  I will replace the baffle on the mutilated one and already have a tweeter for it.  Once I've got the basics together I'll decide on the next step.  One thing I don't understand is the capacitor was attached between the rheostat and the negative terminal of the speaker, with the negative terminal of the tweeter connected to the middle terminal of the rheostat, and I was quite surprised they are 25 ohm.

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Good luck with this resurrection. Have you tried contacting Huw Powell at Human Speakers? https://www.humanspeakers.com/e/epi110.htm

According to the product description and the schematic, these are 8 ohm speakers and the crossover should not be wired as you describe.

epi-110.gif

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On 3/21/2020 at 5:48 AM, Guido57 said:

....replaced the crossover with the common EPI setup of a 10 uF capacitor parallel to the tweeter while adding a 1.5 ohm resister. 

Hi Guido - - - my comments are based on limited experience with the EPI-100, which uses the same drivers and crossover configuration as the 110 model. I want to mention that the cap in this circuit is in series with the tweeter (not parallel), and also ask where you've seen this notion of a 1.5 ohm resistor.

Pic attached shows original EPI-100 crossover, which appears to have wiring connections very much like the one shown in your pic. (Pay no attention to the 8uF cap value rather than the typical 10uF - - this remains a mystery that has not been solved.) I know the wiring does not look exactly like the schematic, but I'm accepting it as accurate since the speakers sound so wonderful. And just like yours, my pot controls are 25-ohm, 5-watt.  

x-o 1.jpg

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Oops, my bad.  I meant to say series, not parallel.  The resistor is in there to attenuate the tweeter while I'm evaluating, cleaning and rebuilding; the pot is currently removed for the process.  It's 1.5 ohm because that's what I had on hand.  Everything is on quick connects for now.  The mystery to me is the cap is on the negative side of the tweeter with the pot between the driver and the cap.

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Finished with a new surround on one of the woofers and installed it into the complete cabinet.  The sound is good.  Next step is putting a new baffle in the hacked up cabinet.  When I have a working pair I'll do some more critical listening and compare them the other speakers I have.

Huw's response to questions on the crossover:

"It's normal, the pot is just something they had to have back then for
fashion's sense. All the way up is "flat".
 
The order components are in when they are all in series does not matter."

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Thx for update on crossover components. I really like having the rotary control in the tweeter circuit, but I think it only showed up in the early issues of their popular speaker models. When you see the x-o replacement that Huw offers for sale, it is nothing more than some decent binding posts, a bit of wiring, and a new (rebranded) cap, all mounted to a small plastic panel. 

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