EPI M250 Advice and insight

[redpackman]

I just picked up some nice EPI M250 speakers. They are not from the same series as you will see from the serial numbers (0396 and 1909) and other differences. If I can read the speaker dates on them properly, I know one at least is 1977 and another may be too, but the remaining two have no discernible dates.  The speakers both have the same capacitor values, two 10 uf caps in parallel each (as you can see from the  photos). They are obviously original because they're buried in the hot glue from the factory. Two are electrolytics and two are the old red "firecracker" type.  Original.  They have tweeter controls on both, different style pots but not the 4 ohm or 16 ohm  selector found on other EPI's with twin drivers in the same cabinet. The drivers seem to be pretty similar.  

The woofers are different. They look to be original EPI's with the square magnets. As you can see from the photo of the front of the woofers, they have different size dust caps. And another significant difference, I don't know if it's a flaw in the speaker or was simply designed that way: In the serial number 1909 one speaker is around 7.9 ohms and the other is around 4 ohms.   What????? All of the drivers "Work" and produce sound. I haven't had a chance to really try them out thoroughly yet though to see if I can pick up any major flaws.

My plans are to put a couple of quality 20 uf (Dayton or Solen) poly caps to replace the four current dual 10 uf caps. I assume that is permissible. 

 I invite any comments or counsel on any of the above.   

[teknofossil]

Perhaps a driver had its voice coil changed with a incorrect part.

-T

[Norman Nicolai]

This is a real puzzler. I don’t have an explanation for why one speaker is testing at 4 ohms and another at 8 ohms. That’s definitely off and perhaps something was replaced incorrectly as another member indicated. I think that some of the other anomalies are probably more easily explained.

For one thing, as you indicated, the speakers are definitely not a matched set. The serial numbers are far apart and one speaker is badged as Epicure and another as EPI. As far as the dust caps, if the woofers were refoamed, which they probably were given their age, the dust caps from the speakers in one cabinet might have been replaced with different sizes during the refoam process. BTW, I’m assuming that the surrounds are foam, given that they appear grey, not black as most EPI rubber surrounds appeared.

Did you know that the M250’s were rated at 4 ohms? The EPI M202’s, a very similar model, were rated at either 4 or 16 ohms.

Here are links to the Human Speakers site for both models:

https://www.humanspeakers.com/e/epi202.htm

https://www.humanspeakers.com/e/epi250.htm

Is it possible that the tags identifying the models are counterfeit, stuck on there after the fact? Could you in fact have 202’s? The 250’s were made from 1976 to 1979. I think by that time EPI had moved on to the 2nd generation tweeter with ferrofluid. The tweeters on your speakers are first generation tweeters from the early 70’s. Also, the first generation tweeters were usually, but not always, matched with woofers with rubber, not foam surrounds.

Perhaps I have been reading too many conspiracy theories lately, but something is off with your speakers.

Please let us know if you figure anything else out. I’m really curious as to how this turns out.

 

 

[Razorhack]

 

On 2/26/2021 at 10:27 PM, teknofossil said:

Perhaps a driver had its voice coil changed with a incorrect part.

-T

Teknofossil has a point here.  Look at the dust caps on the woofers.  There are two that are rather large.  The smaller ones would be what EPI used.  Not sure where those larger ones came from and what else has been done to those drivers.  If they are the ones testing out at a 4 ohm's, someone changed something.