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Pete B

EPI 100 Restoration

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I've always wanted a pair of EPI 100's in real wood veneer and a pair came up locally in nice 
outside condition.  When I pulled the grills one woofer had the cone popped out about .5" or more.

The amp had gone DC and that completely tore the spider to VC former glue joint. I covered
repair of the good woofer and a replacement in this thread:

  http://www.classicspeakerpages.net/IP.Board/index.php?/topic/10671-epi-100-woofer-refoam-and-glue-joint-repair/

I tested some of the older masonite faced EPI tweeters here and found temperature dependent 

behavior:  https://audiokarma.org/forums/index.php?threads/epi-inverted-dome-tweeter-issues.824827/

These tweeters tested without problems and I'll add the results to that page when I have a chance.

 

This is essentially a stock restoration with a lot of attention to detail.  These match the below pair pictured on this page 

but with foam edge woofers rather than the rubber ones shown.  Also note that the early EPI-100 had a level control on

the tweeter, these do not have them but I am adding 50W Lpads (from PE) because I know that they sound better with

some tweeter attenuation.  Two schematics are shown here, one with just the standard 10 uF cap and another with the

cap and the 5 ohm rheostat.  Note that the drivers are wired in phase:

http://www.humanspeakers.com/e/epi100.htm

 

Everyone wants pictures so here are a few of the finished speakers:

Front, note the correct filled fillet foam on the woofers:

EPI-100-F2.thumb.jpg.fa9a4602d9747a0f5b39cd759ffd016f.jpg

 

Back, I didn't bother to clean the old glue residue but I did add a 50W L-pad and upgraded gold binding posts:

EPI_100_BK.thumb.jpg.6a46e0e7d2dd442cb72d39cbdc1a84d1.jpg

 

Front, the grilles are near perfect but I'd prefer white Irish linen from 123 Stitch, perhaps someday:

EPI-100-FG.thumb.jpg.748e0a452c667bcacb29519fed0c32bd.jpg

 

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This is what the stock, cheap binding posts look like:

CHEAP-TERMI.jpg.341d04462c39a8399e884c33348fbef6.jpg

I gripped the plastic push terminals with pliers and twisted about half a turn back and forth about 10 times,

then just twisted hard until they broke off.  You can't be sure if this will work so don't do it unless you are

okay with replacing the entire terminal.  There are 3 slots that held in the old posts and the outermost 

ones are at exactly .75" spacing which is correct for dual binding posts.  I drilled them out for a tight fit

to the Big Post (from Madisound) hex binding posts:

DRILLED.jpg.521813d18d69759172515e3a56ea782f.jpg

 

The terminal board is very thin at about 1/16" and the masonite is only 1/8" so I decided to back it

up with a 4X5" piece of 1/4" MDF.  The crossover board was not glued in with much glue so I ran

a bead of carpenters glue over it.  Drilled the Lpad hole through both boards and glued the 1/4" backing

MDF to the now cleaned off and blank crossover board.  I also filled the empty hole around the back

of the binding posts with epoxy wood filler, had the type that you slice off and knead handy to fill

the two remaining slots and give the new posts a more solid base:

BACKING.jpg.7d5bea1a4fb84b851f406c8616dcf694.jpg

 

And with the Lpad to clamp the boards together:

LPAD.jpg.53ce92f0e55237226b9cd64eaea64e95.jpg

 

Finished close up, knobs are not needed but Radio Shack  274-0403 1/2" blue look nice and are still available on ebay:

Put the knob on so that full up is at 3 o'clock, then up should have the right tonal balance for most people, full off is

never used and 9 to 3 o'clock is the useful range.

EPI-100-INPUT.jpg.e8ddfb47afa245b8547dc59781c23690.jpg

 

Dual binding posts fit perfectly:

DUAL-BP.thumb.jpg.baba10470affdab99446cf3c0728568f.jpg

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I solder directly to the threads of the binding posts in order to provide a gas tight connection to the posts.

The woofer (black) and tweeter (yellow) grounds are soldered to the negative post, an extra black wire is

also soldered to go to the ground terminal of the L-pad.  A 10 uF 1% Dayton poly cap connects from the

positive post to the input of the L-pad, the woofer positive (red) also goes to the positive input post.  The 

cap is glued down with E6000.  Tweeter positive (red) is wired to the center terminal of the L-pad.  The 

picture is blurry and while the solder joints look cold they are actually well done.  All connection are hook

type for mechanical strength, then soldered:

IMG_20190612_214450.thumb.jpg.41e608dbdb5104b6dba9bc190d69295c.jpg

 

Used the stock wire, but soldered the wires to the slip on terminals.  Clean the brass first with a nail file or

sand paper.  This shows bare wire past the crimp bent back over and soldered:

TERM1.jpg.954bfd474114405ecca2854e44f26555.jpg

 

Other times there is some bare wire right below the crimp where it can be soldered:

TERM2.jpg.f41fd7716765cf6d0aaacc8c7886a699.jpg

 

I might use these for testing drivers but, obviously, one could snip off the slip on connectors and solder directly to

the drivers.  Give the slip on's a shot of DeOxit for long term stability.

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I'm keeping these in my collection.

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It is interesting that these are rated as 4 ohm DC and 8 ohms nominal which is stretching

the truth a bit.  They certainly are 4 ohms DC and then dip to below 5 ohms in the bass and

about 6 ohms in the mid treble.

The woofer Thiele and Small parameters are now posted in the woofer repair thread and it is 

clear that these are true acoustic suspension woofers.  I was very curious to measure the woofers

in the closed box system.  Here are the results:

Rdc =  3.95  3.94  ohms

Fc =  48.4  49.5  Hz

Qtc =  .90  .96

I was surprised to find a low Fc of just below 50 Hz and with Qtc being .9 ish they should be

down about 1 dB at 50 Hz, nearly flat.  I'd guess that the 45 Hz rating is -3dB.

Here is the input impedance for system PLB-1:

PLB-1.jpg.4a425b112128d3c37b6af45c4910f7d6.jpg

 

And Zin for system PLB-2:

PLB-2.jpg.fba7a5a03d1369ae01a7eb2ff7d37c5c.jpg

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I've been listening to them all afternoon today and I never owned a pair, never saw an input impedance plot,

my guess was that they'd have an Fc of 60-70 Hz - what a surprise with the Fc at 49 ish Hz.   They really have

nice bass depth and impact, not as good as Large Advents but very close.  They sound very smooth and

balanced with the L-pad straight up (about 3 ohms in series with the tweeter).  Nice detail provided by the

extended response of the tweeter.  I'm really enjoying these.

 

They are placed high in the room, on top of LAs that are also on low stands and they sound like they could

use a dB or two of baffle step but this might also be fixed by placing them on a low stand closer to the wall.  

 

My younger son commented that they sound a bit, just slightly flat (as in depth), and this indicates not enough

baffle step.  Overall he liked them very much.

I've said before that these are one of the best sounding American made vintage speakers period  I wish that

they did not need a sub and the Genesis 2 is the answer to that issue providing response into the low 28-30s.

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Thanks for a great restoration post on a great speaker that doesn't get enough recognition. 

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Hey Pete,

Very nice restoration-mod project with the addition of the L-pad and robust wire terminals. These are a great speaker model and yours appear to be in very fine condition. According to info from Human Speakers, your black plastic tweeters with phenolic dome incorporated ferrofluid; whereas the earlier paper dome masonite tweeter employed a foam and silicone suspension/cooling.

I have an early pair of 100's that are placed about 7 feet high atop shelves full of folded clothing and  connected to a modest NAD receiver that nicely fits the shelf depth. My speakers have rubber surrounds, masonite tweeter, and the original pot control - - very nice veneer, too.  It makes a great little bedroom rig - - these speakers are classics.

epi-100's.jpg

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Hi Robert,

Those look very nice, I've never seen the rubber edged version in real life and I wonder if there is

any difference in the sound.  And thank you for the nice comments.

Pete B.

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Found some newer (to me) Playing for Change tunes and made a playlist here that I've been listening to:

 

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Quote

Thanks for a great restoration post on a great speaker that doesn't get enough recognition. 

 

Hello, Martin. I'm surprised that you like the EPI 100 given your praise of Dynaco speakers (not that I don't admire the restoration done here, great work) but these were really highly reviewed by Consumers Reports. I remember rude high pressure sales people, now out of business decades later, they denigrated the Dynaco A25 they had to demo against, along with the AR-2AX. 

Personally, I found them too bright (didn't an AR designer say "Who would want to listen to a flat to 20KH speaker?) and monochromatic: I couldn't hear details I heard on the USS driver Dynaco, differences between recording studios and techniques, voices weren't as pleasant, etc.

In fact, probably a better cheaper choice now is this much hyped Elac Debut, not as bright to me as EPI 100.

https://audioplacebo.com/elac-debut-2-0-b6-2-review/

I'm using Emotiva UMC-200 for digital sources, and changed to Emotiva BasX amplifiers, the Chesky demo disk is heart breaking because their recording techniques leave the big labels in the shade, I wish so many great singers and performers had engineers with their talents. 

https://www.amazon.com/Ultimate-Demonstration-Disc-Critical-Listening/dp/B00002MXUH

Anyway, I wish you all a Happy New Year. I think the retro speakers might outperform in musicality many of these modern offerings but I wasn't fond of EPI. Not as bullet proof as the Dynacos.  Foam surrounds, etc. And that harsh character I noted. Accuracy is more than "flat" response, IMHO.

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Well, I'm surprised you're surprised that I like the EPIs so much. Since their introduction, I always felt they gave the A25 a good, solid challenge. Over the years,  I've owned two pairs, I think, as well as one bigger pair that had the equivalent of two 100s in each cabinet. All were first-rate, satisfying speakers.  I will reread those old, priceless (some would say, "clueless"), CR 1970s speaker articles to refresh my memory. 

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Hello, again, have you heard Huw's Human speakers and what do you think? It's interesting, Pete, you enjoy/appreciate the classic Dynacos and the EPIs. Your thoughts on the differences?

https://www.humanspeakers.com/human/81.htm

A speaker designer for a high end firm was kind to reply to my questions via email:

 

Quote

I haven’t really spent any time with EPI or Human speakers, other than my friends dad having a pair.  They did have a great tweeter for their era (similar construction to the Focal tweeter, where the dome isn’t driven at its periphery).  However, there is a very non-flat response to the tweeter and there are now tons of fantastic domes available on the market, if you want to go that direction.

The problem with the Seas speaker that you mentioned [The A26] is that this approach, a 2-way a large midwoofer playing up rather high (2 kHz for a 10” woofer) causes a very non flat power response.  The woofer is much narrower in coverage at the crossover than the  tweeter.  Also, the large 35 mm tweeter is much more directional at high frequency (and a 1” dome), which has the same issue (the tonality on vs off axis is critical). 

I would check out this book (summarizing 30 years of research funded in part by the Canadian government) on the topic. 

 
I'm not saying that it is bad, but it certainly far from optimal in a number of ways.  I know that it is an improvement on a classic design and there is something to be said about simplicity in crossover design but that just doesn’t jive with the science of what factors contribute most to the best sound quality.

I'd appreciate your thoughts and if you've no issues, I'll use on my blog:

https://thefrugalaudiophile.blogspot.com/

Thanks! You do great work, Pete. Congratulations.

T.F.A.

 

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16 hours ago, Martin said:

Well, I'm surprised you're surprised that I like the EPIs so much. Since their introduction, I always felt they gave the A25 a good, solid challenge. Over the years,  I've owned two pairs, I think, as well as one bigger pair that had the equivalent of two 100s in each cabinet. All were first-rate, satisfying speakers.  I will reread those old, priceless (some would say, "clueless"), CR 1970s speaker articles to refresh my memory. 

OK, thanks for your reply Martin to the Poodle. To me, the characteristics were different, perhaps Dynaco tried to compete with EPI with the A25XL which never took off and the company, acquired by Tyco conglomerate, of course died. See my comment to Pete on the 21st iterations of Dynaco and EPI. If you've heard them, let me know.

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Pete, I'm wondering if you might consider bringing these to the winter Frankenfest.  When I was speaker shopping in the 70's the only place around here that had the EPI 100 didn't have them hooked up and the sales person I was dealing with did not want to take the trouble to connect them.  Considering the line of BS he laid on me in reference to the speakers on display I never had the urge to go back.  I finally ended up with NLA's and have never heard the 100's, though I have heard a pair of Genesis 1's.

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Hi,  Yes sure if I have room I'll bring them.

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On 12/30/2019 at 2:16 PM, Vicious-Poodle said:

Hello, Martin. I'm surprised that you like the EPI 100 given your praise of Dynaco speakers (not that I don't admire the restoration done here, great work) but these were really highly reviewed by Consumers Reports. I remember rude high pressure sales people, now out of business decades later, they denigrated the Dynaco A25 they had to demo against, along with the AR-2AX. 

Personally, I found them too bright (didn't an AR designer say "Who would want to listen to a flat to 20KH speaker?) and monochromatic: I couldn't hear details I heard on the USS driver Dynaco, differences between recording studios and techniques, voices weren't as pleasant, etc.

In fact, probably a better cheaper choice now is this much hyped Elac Debut, not as bright to me as EPI 100.

https://audioplacebo.com/elac-debut-2-0-b6-2-review/

I'm using Emotiva UMC-200 for digital sources, and changed to Emotiva BasX amplifiers, the Chesky demo disk is heart breaking because their recording techniques leave the big labels in the shade, I wish so many great singers and performers had engineers with their talents. 

https://www.amazon.com/Ultimate-Demonstration-Disc-Critical-Listening/dp/B00002MXUH

Anyway, I wish you all a Happy New Year. I think the retro speakers might outperform in musicality many of these modern offerings but I wasn't fond of EPI. Not as bullet proof as the Dynacos.  Foam surrounds, etc. And that harsh character I noted. Accuracy is more than "flat" response, IMHO.

My interest in the EPI 100 s started with my brother mentioning that they were recommended by Stereophile,

back when they first came out, I also read very positive reviews in the magazines.

I think it was a C or D ranking but at least they got a recommendation.  I went out to listen to them and they

did indeed sound very good.  Their strengths are deep bass roughly to the mid 40s, smooth midrange, and

a clean extended high end to at least 15 KHz if not 18.   On top of it all they sound VERY good and real, like

music in the room.

Note that there is a version with a tweeter level control and others without, I would always add the level

control because they sound best with about 3 ohms in series with the tweeter.  Yes, they are bright without

the control but there is a simple solution get the correct version or add the level control.

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On 1/30/2020 at 4:02 PM, Pete B said:

Note that there is a version with a tweeter level control and others without, I would always add the level

control because they sound best with about 3 ohms in series with the tweeter.  Yes, they are bright without

the control but there is a simple solution get the correct version or add the level control.

Thanks, Pete, this explains a great deal. The Human Speaker 21st Century version of the EPI has no such level control so for that reason I'd avoid it. I see mostly engineer background on this site and I have none but I wonder if you check my comment on the Dynaco restoration whether you agree with Holt's remarks as a listener. Do you listen to Classic Speakers at home and what are you using? 

Here's the link:

https://www.stereophile.com/content/whos-right-acccuracy-or-musicality

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@TheFrugalAudiophile  I printed out and tried to read Holt's article.  I like Holt he 

did a lot for critical listening and wrote some great reviews.  I actually find that 

article hard to read because, in my opinion his logic is flawed.  I have a very different

perspective on audio, I prefer an A/B switch and a reference system.  If you trust

the reference, you'll quickly hear flaws in inferior systems and perhaps a system

will sound even better than the reference but it makes it easy to remain honest.

It is a very complicated subject due to placebo and expectation bias.

I'll try again to read Holt's paper and see if I can put my objections into concise words.

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@TheFrugalAudiophile

It is interesting that you ask what I listen to at home.  I'm a speaker collector but one of

my favorite designs is the PSB Stratus Gold.  I always admired KEF 105 s and B&W 801 Matrix

series II which I'll probably add to my collection someday.  This is the B&W 801 that I admire but

with the flaws fixed, pg 96 in the .pdf:  https://www.americanradiohistory.com/Archive-All-Audio/Archive-Audio/90s/Audio-1990-11.pdf

The main flaws are that one of the iron core inductors in the woofer path saturates,

it should be air core (no saturation), the woofer has DC offset issues "oil canning", all

issues at high power.  VanAlstyne also found that one of the woofer inductors couples to

one of the midrange inductors - the simple solution is to desolder and move one of the

inductors.

Here is the Stratus Gold which has all air core inductors and does amazingly well in

the high power testing, note also the very flat frequency response, page 50 in the .pdf:

https://www.americanradiohistory.com/Archive-All-Audio/Archive-Audio/90s/Audio-1991-11.pdf

All of these systems are large and rather complex but take the listening experience to 

another level.

I've A/B ed the OLA with the PSB Stratus Golds and while the Advents have deep bass

the PSB s go much deeper and will play about 9 dB louder (a lot).

 

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@TheFrugalAudiophile

I started building speakers as a very young kid and read everything I could find about them.

I read about IMF Transmission Lines (TL) and was very impressed with their bass performance.

I tinkered around with them, built some that could shake the room with deep bass, and studied

them as a senior project in college.  My project advisor suggested that it should be possible to

get as good bass as a TL with a vented system (ported or passive radiator).  I did not have time

to explore this but I believe that the Stratus Gold is a good example of how a vented system

can provide as good if not better performance than a TL.  The formula is a big box, low port

tuning (Fb) and high port area for minimal turbulance (minimize compression) or a passive radiator.

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@TheFrugalAudiophile

I've always been interested in anything that can improve the listening experience and

I became interested in "time alignment" and "linear phase" designs, sometimes now

called "transient perfect" or "quasi-transient perfect".

I went to hear the Dahlquist DQ-10 and always thought that they sounded good but

never fully believed the hype about time alignment. 

This is a story that should give a laugh and pertains to EPI/Genesis:

When I was in college I became a member and was reading the Audio Engineering Society (AES)

Journal.  There was a lot of hype in the press and an AES paper from B&O about their 

filler driver method for designing a "Linear Phase" speaker.  I was lucky enough to have at least

4 HiFi stores within 15 miles of our home.  One had the B&O speakers and I went there to

hear them, in those days they offered an A/B switch and could patch in any two speakers.

The young sales guy said sure I can demo the B&O speakers, here's a mid (high) priced model.

I thought the bass is not even as good as Large Advents, and they were not at all musical.

Then the kid says, do you want to hear some good speakers?  I said sure, he patched in the

Genesis 2 speakers on the B side of the A/B switch and said these are half the price.  I was

shocked bass significantly better than the Large Advents and a smooth, musical midrange

and top end.  I said I don't want to hear anything more from the B&O s and I could listen to

these Genesis 2 s all day long.  I never bought a pair, my big TL speakers were better but 

suggested them to others:

https://community.classicspeakerpages.net/topic/3874-genesis-ii-rebuild-design-comments/

They are an EPI 100 in a bigger box, with a passive radiator:

http://www.humanspeakers.com/genesis/gen2.htm

I just in the last year or so added a pair of Genesis 2+ to my collection in real wood:

https://www.humanspeakers.com/genesis/gen2plus.htm

They compare very well to PSB Stratus Golds same deep bass but have about 6 dB less

max output in the bass.  Much simpler design and probably a sweet spot for cost/performance.

There have been several scientific articles in the AES demonstrating that linear phase is not

important to humans in the home listening environment and this demo drove that point 

home for me - B&O vs. Genesis 2.

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I bought a used pair of Vandersteen 2 Ci s years after finishing college in order to 

reverse engineer them and hopefully improve my speaker design skills:

https://audiokarma.org/forums/index.php?threads/vandersteen-2ci-design-overview-and-xo-schematic.913010/

Was not impressed with them.

 

I became interested in the SPICA TC-50 when they came out years ago because of the rave reviews

and linear phase design.  I finally reverse engineered them years later, I'm not impressed with them:

http://baselaudiolab.com/MR-TC50-REB.html

 

I also reverse engineered the PSB Stratus Golds and I do like them, great design but

I never published the work other than the crossover schematic.  I also helped a friend

roughly "clone" them in the late 90s - he says he's never letting them go.

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