Need input restoring Celestion SL6Si crossovers

[thrasher]

Just took the bull by the nads and bought a pair of Celestion SL6Si's on eBay. I expected to do a little restoration and to find information somewhat lacking. But I was optimistic. These bookshelfs are in decent shape to look at, but turns out they sound terrible - no bass, poor mids and definitely not the highs you'd expect (and the guy on eBay described them as sounding "really good").

Both rubber surrounds for the woofers have thin 1-in.+ cracks. And apparently the capacitors are badly deteriorated since the highs are nearly missing altogether, yet the aluminum-domed tweeters appear intact with no dents etc. Overall resistance is 5.6 and 5.7 ohms, which is too low. Nevertheless, I decided "What the hay! This is just the challenge I need."

My amp is an HK 3490 with 120 wpc. I understand the SL6 series is very power hungry but my HK should crank out enough watts to make them happy. Also I just ordered a pair of butyl rubber surrounds from eBay that should resolve the cracked-woofer issue.

What has me stumped is the caps in the crossover have writing on them that might as well be Nordic runes. Maybe it's Celestion speak?

The big cap says EXPOTUS 10-0J250V SP6201 9036
2 smaller caps in series say EXPOTUS 6-0J250V SP6199 9031
and EXPOTUS 4-0J250V SP6200 9031

If anybody knows how to translate the above to uF without guessing and/or any further particulars about the caps pictured below and their crossovers, I would really appreciate it. An SL6Si schematic (in English) would be the ultimate. But again I'm being overly optimistic.
And if/when these are fully restored, I'll be posting more images thnx

 

[Bucky Badger]

PM sent.

 

[musichal]

5.6 and 5.7 ohms sound about right to me for DCR. If too low, what should they measure?

You aren't expecting 8 ohms, are you?

 

[thrasher]

musichal,

Yes. And I see your point. I just did some review and ohms should be about 75% of impedance, in this case 75% of 8 ohms.
http://www.prestonelectronics.com/audio/Impedance.htm
Therefore, as you say, "5.6 and 5.7 ohms sound about right for DCR". I stand corrected.

The assumption was the caps must be bad, especially considering the caps must be 25 years old and even the rubber surrounds have deteriorated some. Assuming they're electrolytic (too many assumptions, huh?) they must be past due for replacement? Do these ohm readings mean the caps are still good, or only that they *could* be still good? Something is certainly wrong.

 

[sreten]

Hi,

The caps are film types and should still be good.
I'm guessing 10uF, 6uF and 4uF, the J refers to
tolerance I think, they are all 250V and almost
certainly polypropylene.

Tweeter DCR is absolutely fine.

Thrash metal speakers they are not remotely.
I wonder what you are comparing them to ?

AFAICR the bass units have a special two
part surround over the original SL6's.
Maybe repair is a better option.

rgds, sreten.

 

[thrasher]

Ok, so at this point it seems we can conclude the crossovers should be working properly. The DCR values are good and the caps are PP film-types which are not supposed to wear out like electrolytic caps do. So the big question in my brain cell is can the cracked rubber surrounds affect the sound of the tweeters when the crossovers are working properly? Is the Celestion SL6 series that extreme?

FWIW, these SL6Si's are intended for Steely Dan and other classic rock in an apartment where lots of bass is not a good idea. The avatar image is John Cale, founding member and maniac of Velvet Underground renown. And I got my handle long before thrash metal. But yeah, it gives a bit of a thrash-metally impression. Maybe the avatar has to go

 

[SoundOfSound]

I believe the caps are actually Mylar/Polyester. Most Mylar caps are wrapped up in yellow for some reason.
http://www.expotus-components.com/filmcaps.html

I agree most likely 4, 6 and 10 uF - 250 Volt - J = 5 +/-% tolerance.

What is that black stuff on the caps? ...looks kinda like mold. it even looks like it may of got under the covering.

My two cents. I'm not sure of the quality level of Expotus parts. I've seen them in stuff but was not overly impressed with the SQ. I'm not saying they are bad just that there is probably better out there today for not much coin.


If these were mine I would do something like this. Remember you can always spend more $$$. Let your wallet be your guide.

Be sure to measure your parts to be sure these will fit.
4.0 uF
http://www.parts-express.com/dayton-audio-dmpc-40-40uf-250v-polypropylene-capacitor--027-421

6.2 uF - close enough
http://www.parts-express.com/dayton-audio-dmpc-62-62uf-250v-polypropylene-capacitor--027-427

10 uF
http://www.parts-express.com/dayton-audio-dmpc-10-10uf-250v-polypropylene-capacitor--027-428

.01 uF bypass cap ...at least on the tweeter caps.
http://www.parts-express.com/dayton-audio-dffc-001-001uf-400v-by-pass-capacitor--027-450

3.3 Ohm resistor. Better ones may help to tame that metal dome tweeter.
http://www.parts-express.com/dayton-audio-dnr-33-33-ohm-10w-precision-audio-grade-resistor--004-3.3

No Affiliation

 

[thrasher]

That black stuff is some kind of foam rubber batting that deteriorated into a fine, smeary powder. It is similar to rotted foam surrounds that crumble. Messy. The batting was originally tucked around the crossovers with regular foam rubber batting holding it in place. Not one of Celestion's master strokes.

Yes, I see a list of capacitor tolerances: "... Capacitors use a wide variety of codes to describe their characteristics, eg J = ±5%. K = ±10%. M = ±20% ..."
http://www.niccomp.com/help/capsubguide.asp
The link is very good for people like me that don't know or forgot how to replace caps.

So sreten, you say these caps are almost certainly polypropylene and SoundOfSound, you say they are actually Mylar/polyester; the Expotus website seems to concur with the Mylar/polyester.
http://www.expotus-components.com/filmcaps.html

There is a risk I'll be replacing caps that are working perfectly. That's a risk I can afford. But does it matter if the caps are polyester or polypropylene? Assuming it doesn't, is one a better choice than the other?

Thanks you guys for the quick, informative responses. Obviously I'd be in trouble without your help.

 

[SoundOfSound]

Depends on what kind of sound you want. Polypropylene are generally cleaner sounding.

Maybe it's a good time to experiment.

 

[thrasher]

Yeah, I see you have PP caps in your Parts Express order list. Clean sound is important to me, so the list looks good. Is a .01 uF bypass cap a precautionary protection against AC noise - something you would do to guarantee quality sound? Just want to make sure I understand what it's for. Otherwise, it's always a good time to experiment!

 

[musichal]

Caps that old, I'd replace. Got the money's worth out of those old ones, now is the time to set it ready for a few more decades - while you have it opened up.

 

[SoundOfSound]

To me it mellows out the sound on tweeters. Gives it a smoother sound and better timbre.

 

[sreten]

Hi,

Thinking about it they could quite easily be mylar / polyester caps.
I overstated the case that they are polyproplylene, which are better.

rgds, sreten.

 

[StimpyWan]

While poly/mylar caps don't generally degrade due to age, they can suffer from being overdriven with too much power. That can cause the caps to fail. So, without knowing the history of the speakers, and the history of the eBay seller, I'd be inclined to replace the capacitors. The PE Daytons are very good, for the money. The PE Audyn Q4's are also inexpensive, and high quality caps.

Good luck!

 

[SoundOfSound]

The Audyn Q4s sound nice too. Good bang for the buck.

 

[thrasher]

PE Daytons and PE Audyn Q4's? Are we now talking about polyethylene caps (PE?) and not PP (polypropylene)? That's fine if you mean polyethylene and it has an even cleaner sound than polypropylene. Not familiar with PE and just want to make sure.

Also would like to know what the .01 uF bypass cap is intended for. (Maybe to filter AC noise?) Not sure.

 

[SoundOfSound]

PE means Parts Express. It's an online store that lots of us get speakers parts from.

.01 uF caps helps the larger cap to perform better. Some say you don't need them but I think it sounds better with them.

It's a subtle difference, not like throwing a light switch on and off.

 

[thrasher]

Thanks. Will go with Dayton polypropylene caps from "PE" since they seem to get a majority vote here. But as far as messing with the existing configuration for the SL6Si's goes, I'm afraid to try enhancing performance with bypass caps when the speakers are already supposedly pretty extreme. Later on I could add bypass caps if it sounds like fine-tuning would be in order :|

 

[SoundOfSound]

Your not really enhancing. It should help to mellow out the tweeter if it is on the kinda harsh side.

All I can say is to experiment with it and see if it works for you.

 

[StimpyWan]

Typically bypass caps are even better, higher quality caps than polypropylene. Usually Film and Foil, or Teflon. The Parts Express Dayton bypass caps are Film and Foil. They're around a buck a piece, so not expensive. I always add them to NPE caps, when I have to use those for larger values. Most users feel that by combining, or cascading two types of capacitors, you also combine the sound qualities of each. So, a bypass cap can improve the sound of a lesser cap. Also, since the bypass cap is such a low value, it helps the larger cap paralleled with it to dissipate faster. Improves the response of the cap, by speeding up it's discharge rate. Many speaker designers feel that this is the true benefit of a bypass cap.

Good luck with the restore.