Epos ES-12 - what modifications?

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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 audioasylum.com (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 | Stereophile.com

TIA.
 
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.

enjoy!
 
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 | Stereophile.com

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.
 
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!
 
Hi,

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

497E12FIG7.jpg


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

An externally hosted image should be here but it was not working when we last tested it.


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.
 
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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 :

http://www.stereophile.com/standloudspeakers/497epos/index.html

http://sites.thestar.com.my/audio/story.asp?file=/1996/11/ksepos

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?
 
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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.
 

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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.
http://www.diyaudio.com/forums/multi-way/223174-interesting-read-i-found-lossy-cabinet-designs-harbeth.html#post3234256

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. :)
 
Hi All. Thanks again for your input.

System7, I think the cabinets might have 1" thick walls from what I have read elsewhere on the internet and 20 lbs per speaker sounds pretty heavy for this size of cabinet to be thin walled (i.e. =lossy). I will not know for sure until I can get inside.

Could be case of insufficient quality sound absorbing material/fill.

There is possibility that corrosion may be affecting the connections as I can see a small amount some surface rust on the metal plates at the back of the cabinet which receives the rods which connect the front to the back faces of the cabinet.

I got to get inside to see! I will post pictures once I do.
 
I have recently replaced the acoustic foam in my Celestion 100 cabinets with Twaron Angel hair to very good effect. I don't know how this stuff compares to the filler in your speakers nor to alternatives like wool, but I suspect it will be worthwhile.

Very interesting product:

TWARON Angel Hair

Please elaborate how you applied the product to your speakers and the before and after results.
 
bolt torque?

I have not yet opened the speakers. I read elsewhere on the internet that the bolts holding the front to the back panel must be at the particular torque but no actual number was given. I did not want to undo the bolts until I figure out the correct torque. Does anyone here have any insight/recommendations?
 
Very interesting product:

TWARON Angel Hair

Please elaborate how you applied the product to your speakers and the before and after results.

I simply filled each cabinet with 60 gms of Angel Hair -5gms per litre. The speakers were full of acoustic foam. Read my "modifying Celestion 100s" thread on here. The improvement was very worthwhile, in particular the low level resolution of the speakers.
 
I have not yet opened the speakers. I read elsewhere on the internet that the bolts holding the front to the back panel must be at the particular torque but no actual number was given. I did not want to undo the bolts until I figure out the correct torque. Does anyone here have any insight/recommendations?
wendle, you ARE being a bit of a wuss here, if you don't mind me saying it. Good God, just open up the flipping case and just avoid overtightening when you put them back together. :D

Being soft plastic baffles, they will doubtless bend if you do overtighten, but rough and ready will doubtless do. Now let's get on with it. :cool:
 
I undid the bolts which all appeared to be the same tightness - just tight enough to hold the speaker together (i.e. not tight at all).

The only stuffing was a small piece if white synthetic batting placed diagonally from under the rear port to the bottom of the woofer.

The single component crossover is a yellow capacitor, 1" diameter x 1.5" long and zip tied to the back panel.

The gaskets for the front and back panel are made from cardboard.

All wired connections were soldered and shrink wrapped.

I will post pictures soon.

I pulled out the existing batting and replaced with long fiber wool which was placed on the bottom and on the back area below the rear port. The capacitor will be done later. I re-assembled the speaker. One speaker sounded lethargic - oops, I accidentally put an extra chunk of wool fiber. After correcting, I had a short listening before bed. The boxy/nasal sound is pretty much gone and bass response appears to be better (perhaps a drop in midrange output). At very low listening volume, the speakers are now listenable which previously had monotonous drone at the same volume. Further listening to follow.
 
wendle, you ARE being a bit of a wuss here, if you don't mind me saying it. Good God, just open up the flipping case and just avoid overtightening when you put them back together. :D

Being soft plastic baffles, they will doubtless bend if you do overtighten, but rough and ready will doubtless do. Now let's get on with it. :cool:

Hi system7, you seem to have forgotten what you said in you post #7:
"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." ;)

I did notice that the different amounts of torque affect the dynamics of the speaker. More experimentation still required.... Originally I wanted to get the torque back to factory spec, listen to the speakers, change the stuffing, torque back to factor spec, and listen again. That did not happen.

I suppose I am trying to mod the speaker there is no right torque (unless one is trying to bring the speaker to factory spec only).

A did an hour of listening and have some more comments. The bolt torque is approximately the same as they were originally by feel. The speakers have improved immensely. The vocals/midrange no longer punctuates the the sound stage with resonant peaks as before but now much smoother/natural sounding. The speakers are much more dynamic and lively - this one was a surprise. Bass response has improved as well. I am surprised how much lower bass there is now. On some piano solos, the sound board sounds HUGE on the lower notes. The highs did improve from the initial listening when I received the speaker to a point where it was listenable. (I wonder if speakers have to be broken-in again if left is storage to many years). There is still some increased roughness that re-appeared after my mod - perhaps due to the much improved midrange.
 
I'm usually cautious in suggesting improvements to a speaker that is evidently carefully thought out. The pitfall has become obvious though. The baffle attachment is a bit of a fussy design. Too loose and the bass is wobbly. Too tight and it will flex (or even break) a soft plastic baffle. What you call a pigs breakfast of a design really. 4 bolts isn't enough for any solidity. :confused:

I would be looking to add some hardwood battens and fix the front baffle with a dozen screws if it's possible. The back panel could also be solid timber, maybe ply.

Might improve things, might make it worse. :D

Wouldn't do any harm to add a 47 ohm shunt wirewound resistor to the tweeter though. Robin Marshall had his reasons for having it in his designs.
 
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