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EPI M100


ra.ra

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I am just writing for help with a quick mystery question.

I have recently acquired and am planning to restore what appears to be an early pair of M100 speakers - - - serial numbers 06341 and 06356. Real walnut veneer, butyl woofer surrounds and masonite tweeter ring. Opening each up to take a peek inside, I was surprised to see that each speaker had an 8 mf cap. Other 100's from a similar age I have seen had the small red and black Callins 10 mf capacitor, which I had fully expected to find. See pics attached.

Any thoughts on what is going on here? Does the 8 mf cap appear original and correct for these early speakers, or did someone replace the originals with an incorrect value? I guess I could do some testing to see what sounds best, but I thought I would first seek advice from the experts.

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ra.ra

I have looked at quite a few EPI speakers over the years and the 10 uf cap has been common, so your pair may have had a substitute cap at some time but I am by no means an authority on this subject. I have also not seen the gray, mortite- like putty on the speakers I have worked on (I assume it was used in your speakers to seal the holes where the binding posts enter the cabinet) so this also could be a clue to your speakers having been modified at some point.

On the other hand, this brand went through a lot of changes over the years and being so simple in design (and cost efficient), it would not surprise me if the manufacturer had several variations during the model 100s' production run and different caps could have been used to keep costs down. Also, keep in mind that with the woofer running full range and just a 1st order xover on the tweeter, the difference between 8.0 uf and 10 uf caps is relatively minimal and many folks would not find it that much different without careful direct comparison.

You might also contact Huw Powell at Human Speakers as Huw is most likely the best "expert" on this brand of speakers.

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Dchristie

Thanks for the great response. I do like these very simple speakers - - heavy duty and no nonsense. Aside from the odd cap value and the grey putty, there was no evidence that these had ever been tinkered with. The speakers still have the (not-so-great) original spring-type wire terminals on the rear, so the factory seal is still intact here - - maybe someone added the putty simply to shield the bare wire leads from the cabinet stuffing? See pic of other x-o with putty removed.

And yes, this model did undergo several iterations over the years, but I think you'll agree that this pair is either the original or a very early variant. When I get around to restoring them, I'll probably just ignore the 8 mf caps and replace them with a good value 10 mf poly cap. Is there anything to look for with the tweeter controls? Any advice on prudent maintenance to be performed, or diagnostic testing of any kind?

And yes, I did contact Huw at the same time I began this post - - he promptly responded with, "looks replaced to me. maybe 8 uF was all they had around?"

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ra.ra

I think you would be fine replacing the 8 uf with a 10 uf cap. For most of my EPI mods, I also replace the spring loaded speaker inputs with high quality binding posts ( as long as you are comfortable with soldering techniques). You could also purchase the whole thing from Huw Powell as he sells a complete xover replacement including the 10 uf caps, wires, and posts all on a new mounting plate but it is really pretty simple to do yourself. Also, unless you really like the ability to adjust the tweeter level, I would bypass the L pad as it really is not needed in EPI speakers as the woofer and tweeter levels match very well without it. If you keep it in the circuit, a little Deoxit cleaner may be needed to clean the internal contacts if it is scratchy from years of oxidation. I also add a cross brace between the front and back baffles and attach it in the area between the tweeter and the woofer.

Also, you might recondition the rubber surround with a proper recoditioning product but this should be done only if the rubber seems to be somewhat stiff due to age.

All of the above is what I usually do for a full mod, but just replacing the old cap with a good quality poly (as you indicated) and cleaning the L pad will get you a very nice sounding speaker for just a little effort.

I have found all of the earlier EPI speaker models and their Epicure cousins to be very natural sounding and very enjoyable overall .

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Thanks again, Dchristie.

I agree with most everything here - - - I'll definitely use 10 mf caps (and not 8 mf), and I'll probably replace with better quality input terminals, too. I like having the tweet control, so that will stay in the circuit but I will give it a spritz or two of De-ox. Do small cabinets like these really benefit from a cross brace? How do you do it - - - maybe a little 1" square wood strut wedged tight between from baffle and rear panel? Glued in place....screwed......or both?

A little treatment on the rubber surrounds sounds like prudent advice, but I do want to be very careful about which product will offer safe and simple benefit and yet do no harm (physical or audible). After reading so much about the various (and largely harmful) products that have been used over the years to try to re-seal cloth surrounds, I'd suspect that the same level of scrutiny is necessary for treating butyl rubber. Not only do I have rubber surrounds on the EPI's, but I also have ADS and Realistic (see below) speakers that seem to use the same material for woofer surrounds.

Here is one discussion on the topic - - - somewhere else I read about some dude proclaiming the magical benefits of using dot 3 brake fluid as a rejuvenating topical application, while others tout the values of cod liver oil. Hmmmm, I think I'll wait awhile, and for now just use soft brushes (for dust) and a damp cloth (water) to freshen them a bit.

http://mail.audiokarma.net/forums/showthread.php?p=3557034

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ra.ra

I usually glue and screw a 1 X 1 inch brace cut to fit snuggly between the front and back baffels. It is probably overkill for most modifiers but the speaker experts do claim that it does help to reduce baffle breathing (movement) and I have added so many braces to modified speakers over the years, that I find it pretty easy to do but it does take time and patience. You can probably live without it as a lot of older speakers do not have this and they sound fine just as they are.

With regards to treating the rubber surrounds, I would only do this if the rubber is stiff or shows some of the symptoms of aged rubber. My Marantz Imperial 5 speakers had a white powder-like exudate on them after years of sitting idle and treating them made them very pliable and softer as well as bringing out the black color. Same thing with my refurbished Dynaco A-25XLs. My ADS 810s are just fine after 35 years and needed nothing done to them. The rubber seems to be in good shape and they look the same as when I bought them in 1978.

As to what to use, I searched extesively the various internet audiophile webs (AudioKarhma, AudioCircle, and Classic Speakers)and finally decided upon a product called 303 Aerospace Protectant. I bought mine at a NAPA auto store and it is made for specifically treating, protecting, and restoring rubber and a number of other synthetic materials. I have had no adverse effects from the treatments and it makes the rubber diaphragms look almost new. Many folks warn against using anything at all on the surrounds but this product has served me well but use at your own risk - I have treated several pairs of speakers with 303 over the past year and the diaphragms still look and work just fine so I am very comfortable using it. From my experience, EPI rubber surrounds usually don't need any treatment, but you must decide for yourself.

Good luck!

Dean

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