EPI 100 Woofer Refoam and Glue Joint Repair

[Pete B]

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.  Desoldered the 

lead in wires from the terminal strip and that allowed me to completely remove the moving parts

from the woofer.  Interesting to note that the VC former is paper rather than a thermally conductive

metal.  I've been informed that the Genesis version of this woofer has an aluminum former and I'll

be looking for those woofers.  More discussion here:

https://audiokarma.org/forums/index.php?threads/epi-100w-foam-popped-woofer.633766/

Obtained another EPI 100 woofer and refoamed it with filled fillet foam, looks good at first:

On further inspection I noticed that very slight pressure on the spider moved it at the glue joint to the

former.  This picture shows the normal gap where about 1/16" of VC former paper can be seen:

 

Next picture shows the gap at about 1/8" with slight pressure from my finger indicating that

the joint needs to be reglued:

Note also, that the Original Advent woofer and many others often require this type of repair if

they are to be used at full output:

I use JB Weld 2 part epoxy for this type of joint for the strength, ability to withstand 

high temps, and availability locally.  A shish kabob wooden skewer is just the right shape to

apply the glue without it getting on the spider.  I apply it in small amounts working it into the

spider and cone at the joint:

 

Once the epoxy was applied the wide 1/8" gap did not want to close up.  I had to put the woofer

face up on a table and put a weight on the cone to force it down and close up the gap - left it

overnight to dry.  I hated to do this since it caused the spider to sag, but the alternative is to scrap the woofer.

Some might try to rebuild it with a new spider but most replacements are often not compliant enough:

 

The glue is very slow drying and I had to leave it over night.  The spider rest position was lower than normal

after sitting for so long.  I use rolled up shopping bags pushed between the frame and cone to push it out

and leave it overnight to restore the correct rest position:

 

Note how the cone is at the full out position with the bags in place:

 

 

Completed job, note how the spider is flat again.  The spider should always be checked for flatness in

case any previous handling might have caused spider sag:

 

I had epoxy glue left over and used it to apply a layer on the magnet over the original glue, not pretty but it should help:

 

Some like to apply damping material on woofer frames and commonly available U-Seal is cheap and

easy to apply:

 

I'll measure these some time soon.

 

[Pete B]

T&S measurements, posting a picture because the forum strips spaces and makes it difficult to format a table:

Note the very low Fs and large Vas indicating that the filled fillet foam has very high compliance as it should:

Parameters pass a sanity check and pair matching is good:

[frankmarsi]

Hi Pete B,  do you feel the insulation-type tape is working, did you notice any change?*

As you know the 'baskets' are stamped-steel and with the bends in such a ridged frame, I'm thinking there wasn't any change or noticeable difference.

What say you?

*  Twenty years ago I bought a yard or so of the car stuff "Dyna-Mat' that I intended to use on a Thorens TD125 turntable I was restoring and hesitated to do so.

I had researched it and thought of it as a great idea. Then, I started to think about the table's manufacturer design and pondered that if they didn't do it perhaps there was a reason.

While waiting to make e decision I did further research and came about opinions that over-damping could have reverse effects was also a consideration. Then, in 2020 I purchased another Techics SL-120 (my sixth in the collection). The previous owner has similar ideas as he used rope-putty to damp the table. He used it on the underside of the table's platter, on all four insides of the cabinet and on various areas on the underside of the plinth.    When I decided to try the table with a SME arm and a $1,000. phono cartridge- it sounded muted and musically un-natural. I knew the cartridges sound quality and it wasn't coming through.

Dynamics were muted, transients subdued and generally all upper frequencies sounded dull. I removed same cartridge and head shell combo and installed it on another table in an identical tonearm on another turntable and all was back to sounding normal w/o the muting of any frequencies and all transients intact.

I still have the yard or so of the 'Dynamite' in its box as my thinking has changed. I continued to research and found more often than not, the people who had qualifying ears and knew what to look for have contrary ideas and advise against it.  

There's even a very small patch of similar material offered for purchase that can be placed between a cartridge and head shell also intended to subdue sympathy vibrations but, the reviews were mixed.

FM

P.S. Thanks again for the Phase Linear manuals.

P.S. II I also own pair of the EPI-100 speakers I found in 2008 that sat out in the rain in the trash. The woofer of course needs to be re-foamed but, the back edges of the press-board vinyl-clad cabinets have slightly bubbled. Might you know if I can firm them up a bit? Maybe I can inject some adhesive into drilled holes in the exposed areas? The board panels aren't terribly bad and luckily the vinyl clad cabinet had protected itself for the most part.

Maybe "geneK" has some knowledge about such matters?

 

 

 

 

 

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