Are the older Micamold caps more durable than the later Aerovox?

[KT88]

I'm looking at the old Type AA of my new acquisition, 1973 Khorns. The first sound impression three weeks ago was not bad at all. Before I do all the restoration work, I have installed parts of my LaSala that I know work well, K55V with new membranes, AA xover with new polyester caps and original T2A. I will write about these Khorns later. For now, I'm only interested in the Xover Type AA.

First of all, cleaning the contacts is a must when you buy such old speakers. It really made a difference in the sound. Sand down all the contact points on the cable lugs and the crossover and clean them with alcohol. My contacts had many layers of what was probably tobacco smoke from five decades. By the way, I also got rid of a really bad smell from the horns, but more about that later.

What I wonder is that I have 1977 LaSala with Aervox caps. The oil had leaked out of all of them many years ago. The 1973 Khorn has old Micamold caps. The 13uF is added from three smaller caps connected together. The sound seems to be good. The values of the capacitors are usable for the time being. Both 13uF values measured slightly less, exactly the same on the left and right at 12.4 uF. The small caps are between 2.02 and 2.2 uF. The caps are absolutely dry. Maybe the climate in Italy is better where I bought the Khorn because they still have the right values and are dry. I can't measure ESR myself, I have to have it done in a specialty shop. Despite the missing ESR measurement, these caps sound very nice, I like them a lot, a bit silkier and more forgiving than the new polyester caps of my other type AA (where the Aerovox were before). But the Khorn yover does not sound cloudy or washed out at all. On the contrary, I have the feeling that the bass sounds more balanced. (Another can of worms for another thread,..Klipsch bass coil vs. Crites bass coil. I don't know if there are differences...The T2A autoformer is definitely completely wrong on the Crites xover.)

Question: Has anyone else experienced that the old

Question, were these old Micamold caps more durable than the later Aerovox caps? Or was I just lucky?

 

In the pictures, among others also dirty contact vs. clean.

 

 

[billybob1]

@Deang...may can say more. Only 4 entries here doing a search.:

 

https://community.klipsch.com/index.php?/topic/148043-1974-heresy-type-b-crossovers/#comment-1688595

 

[mikebse2a3]

14 hours ago, KT88 said:

Question, were these old Micamold caps more durable than the later Aerovox caps? Or was I just lucky?

 

I suspect maybe “lucky” 😀

If you look at antique radio website comments it seems they have issues as any other brands.

 

I would suggest testing Leakage before assuming they are fully in specification.

 

Maybe it would be worth investing in a good capacitor tester with leakage testing capability if you would like to keep the Klipschorns as original as long as possible.

 

miketn

[KT88]

5 hours ago, mikebse2a3 said:

 

I suspect maybe “lucky” 😀

If you look at antique radio website comments it seems they have issues as any other brands.

 

I would suggest testing Leakage before assuming they are fully in specification.

 

Maybe it would be worth investing in a good capacitor tester with leakage testing capability if you would like to keep the Klipschorns as original as long as possible.

 

miketn

 

 

 

If I remember correctly, DC leakage parallel to the dielectric is fatal for tube amps when a coupling cap is suspect, but what sound effect does leakage of a cap have in the crossover?

 

I think too high ESR, as DC resistance in series with the cap, makes the sound quieter and duller, or am I wrong?

 

Yes, I should know leakage and ESR values. If the values have gotten out of hand, I still have a completely new unused package of JEM for the AA xover, which I originally bought for my LS, together with a Klipsch forum member from the Netherlands, so we had shared the shipping costs. But I think the sound with the old caps is not quite as “dry and sober” as with the new polyester types (even though I'm not using the unused JEM ones at the moment). But I bet I won't hear much difference with the new dry polyester types. It's a shame that these old “Klipsch” caps are no longer available new. And any other old paper oil types can also be an expensive risky experiment because they can end up sounding very dull. We know that Klipsch used polyester in oil.

Oh dear... I want to stick to the topic of the original Klipsch restoration and not expand the discussion to third-party suppliers. So I will try to have my caps tested in a specialized workshop or, if it doesn't cost an arm and a leg, buy a test device like you suggest.

 

At the moment, the speakers don't sound bad to my ear, but I know that you can imagine certain aspects and euphorically hear things that aren't there. But in a week or two, I might notice what's being masked in the sound when the values are no longer right. At least that's happened to me before.

 

Edit, next weekend I will try JEMs and compare them with the old original ones. I could imagine they will deliver a bit more mid sound energy and better intelligibility. because that are the areas where the silky old ones are worse than the non JEM polyester types and certainly the JEM as well.

[KT88]

JEM polyester vs. 51-year-old Micamold capacitors

I received a set of original JEM type AA in February and installed them in the 1973 Khorn yesterday, replacing the Micamold caps. It was a positive shock. Compared to the old Micamold, the JEMs make the Khorn noticeably louder. A super clear mid-range articulation, very good intelligibility, a seamless frequency response without annoying boosts anywhere. I thought that I really liked the somewhat silky sound of the Micamold and I was afraid that I would lose this characteristic when I exchanged them.

But what can I say, the JEMs are incomparable better and so well-balanced. The bass is very energetic, the mids very complex and the treble clear and spacious. I don't miss anything from the Micamolds, goodbye forever. They were simply worn out, even though the capacitance values were still correct.

 

I can recommend anyone who has a well-maintained but old Heritage speaker to replace the capacitors. My Micamolds were dry, looked good and were in a room in a very good climatic zone in Italy. And nevertheless they became electrical cripples after 51 years.

 

Just to give you a small example, many of you will know “Dreams” by Fleetwood Mac. I first changed only one type of AA and compared it in mono with the old Micamold. It's no comparison! If you didn't know it better, the sound with the old Micamold could be ok. But with „Dreams“ (as with many other songs afterwards), the difference was immediately apparent in many respects. At the beginning of the song, you could hear the snare drum very clearly for several bars, without many other instruments and without vocals. With the worn Micamold caps, I only heard the normal snare drum skin. With the JEM, it became clear that it was a very full and mighty snare drum sound. I could hear that the drummer must have played a fairly large snare drum. It has simply become a powerful, expressive speaker. So far, the change from Micamold to JEM has been the most valuable and important single measure in terms of improvements towards originality. In the photos below, you can see that I still like to use the original cables from the 51-year-old AA.

 

The expensive thing about @JEM is the special capacitance values for the AA, which are not commercially available. Perhaps the JEMs are also qualitatively better than the polyester types from other well-known suppliers in other respects, I don't know. At least the JEMs sound absolutely great and more silky! than my other Polyester caps of the LaScala Type AA and if I were in the USA, they would always be worth it for my vintage Heritage speakers.

 

Now I live in Europe, but still! it was worth it to me to get original Klipsch approved caps with the special mF values.

A few years ago,  @Chief bonehead pointed out in the forum somewhere how important it is to strictly adhere to the mF values for the Type AA xover. If I remember correctly, he explained that the subsequent 2mF drift further away in their function if the preceding 13mF is not absolutely correct.

The 2mF from JEM are wonderfully accurate.

Therefore I take it with a small grain of salt that the 13mF show 12.66mF and 12.74mF. My measuring device is correct, for comparison, see a picture with my 13.1 mF self-assembled 13mF of my other AA for the LaScala, also taken yesterday.

 

Sorry, I don't want to appear pedantic, but if I end up spending serious money on 6 polyester caps delivered to Germany (even if I could happily share the shipping costs with another forum member from the Netherlands for his set of JEM caps @ronajon  then a little more careful measurement before the trip across the pond would have been a nice measure. Now I can't ask JEM regarding a possible exchange anymore, considering the customs, shipping and import sales tax costs. I'll have to add 0.33mF in parallel.

 

Nevertheless, no misunderstanding, I am very satisfied with the sound of the JEM and can only recommend it again. It has not “improved” my 1973 Khorn, it has “transformed” it, quite seriously.

 

 

[mikebse2a3]

1 hour ago, KT88 said:

Therefore I take it with a small grain of salt that the 13mF show 12.66mF and 12.74mF. My measuring device is correct, for comparison, see a picture with my 13.1 mF self-assembled 13mF of my other AA for the LaScala, also taken yesterday.

 

Heinz considering the capacitors are rated at within 5% of specified value yours are really good at 2.5% within spec.

Another factor I believe should be taken into account is that It’s very likely that the HF drivers themselves have a much higher tolerance variation in performance within their specifications thus I would be really surprised if this was an audible factor.

 

My thinking is if Roy specified 5% tolerance for the capacitors (and yours are only 2.5% off) then I believe it’s safe to assume that any variation within that range will still give you the sound he has designed for. 

 

Of course it can’t hurt to bring them up to 13mfd 🙂

 

miketn

 

 

[KT88]

4 minutes ago, mikebse2a3 said:

Of course it can’t hurt to bring them up to 13mfd 🙂

 

miketn

 

 

Thanks for your Kind reply, Mike. It should also not be taken too much as a major point of criticism. I hope I have been able to describe how happy and satisfied I am with the JEM caps. I hadn't even thought about the deviations of the 50-year-old K77. And even though that is the case, they still sound quite the same to my 65-year-old ears 🙂

I'll just try it out... whether the JEM alone sounds better than the addition of another small polyester cap, i.e. the sound of the caps connected together vs. the correct value. And here too, I agree with you, 2.5% is very little tolerance in the world of capacitors.