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wendle 1st December 2012 07:20 PM

Epos ES-12 - what modifications?
I acquired a pair of Epos ES-12 in decent shape. I did a google search of modifications for this model and did not find much information except for some info on (Epos ES-12 nasal sound in midrange) from year 2000.
I did find a lot of info on the ES-14.

Has anyone here done any alterations to this speaker? Results?

As this speaker is very old now and can be purchased used for a reasonably low price (in 1997 it listed for $1100).

Stereophile stated "might well be the loudspeaker bargain of the year":
Epos ES12 loudspeaker |


sharpi31 1st December 2012 07:56 PM

without knowing anything about this particular speaker's crossover......

i'd look at the (hopefully) film caps in the crossover and replace these with closely matched better quality film caps of your choosing. i like good industrial polypropelene in oil caps like epcos mkv and asc. then i'd look at the higher value electronic caps, if there are any, and replace these with film caps (with possibly a small series r if the original electrolytica had high esr) or at least better electrolytics.

this approach tends to lift the performance of most off the shelf designs.


system7 1st December 2012 08:00 PM

There's really very little to alter on it, if it's like the Epos ES-14. Single 2.2uF non-polar capacitor filter to the tweeter. :D

Robin Marshall: A Modicum of Genius Page 5 |

I suspect Robin Marshall would have fitted a MKP capacitor if it sounded better. But electrolytics do age, so might do with replacement. The bass driver is a beauty. Underhung voice coil and natural rolloff without filters.
ES12 | Epos Acoustics

I suppose there is a danger the ferrofluid in the tweeter is drying out now, but that's all.

sharpi31 2nd December 2012 10:20 AM

I used to have a pair of ES11s (long term loan) and forgot that the crossover was so simple off these designs. I loved the ES11s - worked great with the Naim and Crimson kit I had back then. At that point in time I wasn't into tweaking, and the speakers weren't mine to meddle with anyway. More recently I owned a pair or Loth-X BS1s that I purchased to work with low power class-t amps. These also have a single cap on the tweeter only. I changed from the stock MKP to a matched pair of Siemens MKV and the improvement was massive.

If it was me, and I knew that the only element in my crossover was an electrolytic cap, I'd have already ordered some film and oil replacements. In my experience it makes a significant improvement 90% of the time (the only potential issue is where an overly bright tweeter is being damped by a high esr electrolytic, and the new low esr film cap makes the sound brighter, but this can be fixed with the addition of a small series r).

You're only changing one cap in each speaker - it will be simple to change back if you don't like the results.

In fact, PM me with your address and I'll send you a couple of 2.2uf film caps free of charge. I'll put my money where my mouth is!

sreten 2nd December 2012 12:53 PM


Measurements (from stereophile) are always good for suggesting mods.

Some possible mods :

1) Detune the port for deeper tighter but not as prominent bass

You could make the port longer, but the easiest way is to line
the port with porous foam, the thicker it is the more it will
detune the port, about 3/8" thick might be right. If the
650Hz impedance blip is the port, it will fix that too.
(Use a piece 3 times port diameter x port length).

My maximum frequency target for any vented box is low E on a bass,
detuning the port from ~ 60Hz to ~ 45Hz should be good if you do 2).

2) If you detune it a lot add a passive line level BSC filter

If you can control the low bass its just begging for some BSC EQ

Baffle Step Compensation is one way of doing it.
I've built a similar circuit into the preamp section of my amplifier.

However a typical baxandall bass tone control will do the job at moderate settings.
If you have one, set the bass by ear, pull the knob off and reset it to 12 oclock.

3) Quality acoustic foam lining

I don't know what is in the speaker, if its minimal, upgrade it.
A piece directly behind the unit, in the middle of the cabinet
but away from the port is also very effective with the lining.

4) Contentious - damp the cabinet

This always causes arguments, as you can't really properly
damp rigid well braced cabinets. but FWIW my flooring grade
18mm chipboard heavily braced cabinets improved with two
layers 1mm solid vinyl floor tiles put their to reduce resonances,
it doesn't eliminate them, but made the boxes sound quieter.

rgds, sreten.

You can't do anything with the x/o, should be a good quality cap.

wendle 2nd December 2012 11:27 PM

Thanks for the responses so far. After some listening I find the sound to be too boxy, closed in midrange and highs too rough. To sum it up - irritating. The reviews I have seen in Stereophile & The Star paint a very different picture of the sound :

I comparison to my B&W 802's, which are floorstanders, the sound of the Epos is awful. The Epos never disappear like the B&W.

Thanks Sharpi31 for your offer for the capacitors! I have sent you a PM. Hopefully this fixes the highs.

How hard is it to remove, and how do I remove, the plastic caps to get to the bolt heads without damaging anything?

system7 3rd December 2012 12:20 AM

2 Attachment(s)
Seems the ES12 was designed after Robin Marshall left. He did the ES11. I certainly see his trademark 47 ohm resistor across the tweeter...:)

It could well be a film capacitor in the ES12, but it seems they lost the Fs damping resistor.

I'd think you get in through the back if it's like the ES11. Those caps ought to pull off to reveal nuts though they might be threaded themselves. This is apparently a job for a dealer to tighten it all up when stuff comes loose, so there might be a pitfall lurking.

davidsrsb 3rd December 2012 06:17 AM

I guess these are about 15 years old, so ferrofluid drying out is very likely

sreten 3rd December 2012 12:11 PM


You should find 4 bolts between the front and back, accessable
underneath the 4 rubber inserts for holding the grill in place.

rgds, sreten.

system7 3rd December 2012 07:24 PM

It might be worth tightening all the electrical connections in various ways to get this speaker singing. Rust plays a part in all old purchases. We shall have to wait and see if the tweeter is past its best.

But mostly, I would try and improve the cabinet.

I'm afraid that thread wandered off into the wilderness after a while, but cabinet damping with rubbery stuff and less fluff is a worthwhile thing. :)

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