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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 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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