Measured Values Of Old SDA Capacitors

DarqueKnight

We sometimes read about how electrolytic capacitors can change values as they age. I was curious about the values of the capacitors removed from my SDA SRS's and two pairs of my SDA CRS+'s. I would have measured the parts from my SDA SRS 1.2TL's, SDA 1C's, SDA 1B's, and my third pair of SDA CRS+'s, but those parts are in plastic bags inside a small box inside one of the big boxes in my attic, and I didn't feel like going to the trouble.

The SRS capacitors are 23 years old and the CRS+ parts are 19 years old. Almost all of the electrolytic and mylar film capacitors and resistors were within 5% of their schematic and label values. The measured values of the silver mica bypass capacitors varied widely from the 750 pF schematic value. The silver micas from my SRS's had no labels at all. The silver micas from my CRS+'s were labeled as 806 pf or 1000 pF.

Capacitor and resistor measurements were taken with an MCP BR2822 LCR meter.

I was curious about the construction quality and tolerance of the mylar and electrolytic capacitors, which were made by Tecate Industries of San Diego, CA. I called Tecate and was told that data sheets for parts that old would be difficult to find because the company typically only retains technical data on parts going back ten years. They advised me to ask Polk Audio if they retained data sheets on components. I'm not holding out any hope that such data will be easily found.

My measurements are summarized in the document attached below.

nms

That's interesting, DK. So re-done X-overs don't sound better simply because the new components are "on spec" and the old ones weren't.

OldmanSRS

Thanks for taking the time to check these. I wondered how much they changed after 20 years. Except for the one silver mica cap, everything was within the 5% spec.

zingo

You out-do yourself every time DK. Nice work.

Face

I was about to test my 30 year old caps out of my Tannoy's. Thanks for the thread.

John in MA

In speaker use, the ESR of a capacitor is just as important as the capacitance. That's a factor that can change with age and muddy up your high end.

It's also why replacing electrolytic or oil can caps with poly isn't always a good idea, as it will change the voicing of the speaker.

hearingimpared

nms wrote: »

That's interesting, DK. So re-done X-overs don't sound better simply because the new components are "on spec" and the old ones weren't.

No indeed, that is far from true.

Sonicaps and the Mills resistors I used to upgrade the stock components sound leaps and bounds better than the original. In my case it took 340 hours to break-in the new components before they settled down and yielded their best performance. At 400 hours they were amazing and they've given me nothing but consistent pleasure.

Ricardo

Interesting; when I "upgraded" the crossover of my 3.1's I measured the old caps and with the exception of the mylars the caps were well outside tolerance.



http://www.polkaudio.com/forums/showthread.php?t=47929&highlight=crossover

Boywonder

Excellent....Great info. I will be re-doing the Xovers on my freshly veneered monitor 10's this weekend (if the box of goodies is on my doorstep tonite). I am planning on an A/B comparison between stock and upgraded, since I am somewhat of an audio skeptic.

I can't spray any more lacquer on my veneer until it stops raining so I'll break out the soldering iron.

nms

hearingimpared wrote: »

No indeed, that is far from true.

Sonicaps and the Mills resistors I used to upgrade the stock components sound leaps and bounds better than the original. In my case it took 340 hours to break-in the new components before they settled down and yielded their best performance. At 400 hours they were amazing and they've given me nothing but consistent pleasure.

No, no, I meant that the reason for the sound improvements people hear from re-done X-overs is probably not due to more accurate components. I'm not saying that new X-overs don't sound better.

analog97

Very helpful information, again suggesting that specs only tell part of the sonic story. There must be several properties of capacitors that are generally not measurable that provide important aspects of sound. I've always imagined that fundamental differences in capacitors in terms of "wave form integrity" (my phrase) must exist and be meaningful.

My Sonicaps and Mills parts for my 1.2TL upgrade are still sitting on my pool table. I want to do it soon, but time is not my friend and the little time I have I want to spend listening. Wow, I like those speakers. But, I promise to do measurements as well and post them. The more data, the better informed we are. Thanks Dark One for the helpful post.:D

nspindel

hearingimpared wrote: »

No indeed, that is far from true.

Sonicaps and the Mills resistors I used to upgrade the stock components sound leaps and bounds better than the original. In my case it took 340 hours to break-in the new components before they settled down and yielded their best performance. At 400 hours they were amazing and they've given me nothing but consistent pleasure.

What he said

DarqueKnight

John in MA wrote: »

In speaker use, the ESR of a capacitor is just as important as the capacitance. That's a factor that can change with age and muddy up your high end.

We have several ESR meters at work and it would have been good to compare the measured equivalent series resistance values to those on the data sheets...if the data sheets were available.:(

John in MA wrote: »

It's also why replacing electrolytic or oil can caps with poly isn't always a good idea, as it will change the voicing of the speaker.

Changing a speaker's voicing isn't always a bad thing. Sometimes a change in component type or quality, with a commensurate change in voicing, comes closer to the design ideal of the speaker. I was definitely thrilled with the "voice change" that polypropylene caps brought in my SDA's.:) Besides, replacing the mylar and electrolytic caps with polypropylene caps in my SDA's was recommended by a Polk engineer.

Dennis Gardner

Shows just how much more important placebo is than farads ....:)

OldmanSRS

Please don't take offense to anything I say here. I'm just trying to get my mind around this break-in improvement people report after the XO mods. I brought this up in another post and was hoping some techies would chime in. This post about the caps seems like an appropriate place to discuss it. I have not performed any mods on my SRS's so I have no way of experiencing the potential improvments first hand.

I still don't understand why 300-400 hours of use is needed to break in the new XO parts before optimum sound quality is heard. The high performance caps and resistors that get installed in the XO mod should by definition not change their electrical characteristics from their designed values with some hours of use. If they did, what's to say they would change in the correct direction, and by the correct amount, and then stop changing when they reached a point where they sounded the best.

If this phenomenon is valid for Polks how does it affect the caps and resistors in all of the other electrical devices out there? Do they all perform better (or worse) after a break-in. I didn't notice any change in my SRS after 400 hours back in 1989.

ESR differences between caps of different materials would influence the sound by intruducing an additional resistance value in series with the frequency dependant capacitive reactance value. ESR's range from a few Ohms on elecrolyctics to a few thousanths of an Ohm on ceramics. Are the ESR's changing over time?

The fact the old caps were still within 5% of their original capacitance sort of supports the no change idea, even after 20 years of burn in. I agree there could be an improvement when using caps of the same value but made of better materials (voice as described above).

Please, one of you technical guys help me understand this break-in quandry.

Thanks

Dennis Gardner

It takes 300-400 hours to forget how many $$$ you blew in relation to the improvement in SQ.

Monetary memory is much stronger than auditory memory.;)

jakelm

I guess its the same reason why engines get better gas milage after 1,000 miles. Gaskets seat better, compression increases, but HP and torque never changes. MPG increases, yet the engine's specs never changes.

It could be that, not the intire cap changes, but the components that make it up do.

OldmanSRS

Shows just how much more important placebo is than farads ....

It takes 300-400 hours to forget how many $$$ you blew in relation to the improvement in SQ.

Dennis Gardner

Dennis, not being on here long enough to know your humor, it seems you have other opinions on the cost effectiveness of the XO upgrade. An XO mod infidel, if I may.

Jakelm, interesting analogy to a car but it's not apples-apples. A car gets better mileage after the rings in the engine seal and the cylinders get smooth reducing frictional drag on the parts. Add that to the tranny and the rest of the drivetrain wearing to a point where friction is reduced and the car gets better mileage. You can measure an increase in TQ and HP on a chassis dyno after the car breaks in.

The new, expensive Sonic caps are as stable as any electrical component can be. They don't wear like the mechanicals of a car. Electrolyctics on the other hand will degrade and/or dry up with time. The degradation is highest in power supply filter circuits and lowest in low power, cool running applications like XO's.

BrettT1

Thanks for the great post, DK.:)

jakelm

Old, my analogy was givin and you made it better. Tranny, seals and rings, all make up an intire car, just like you have individual parts in a cap. As you pointed out, after milage, the car perfomance is better. Cant the same be said about a capacitor? Just a part that is alittle mroe difficult to measure? A part(s) that deal with other things becides capacitance.

I agree with you for the most part. A cap value does not change between hour 1 and hour 400. But I have heard, from my own experience with upgrading my 7's xover, that after a few hours of playing time, the speaker, with the "new" xover, has a different sound and characteristics.

heiney9

OldmanSRS- If you have specific questions about capacitors and really want a guru's opinion give Jeff at Sonic Craft a call. He is always willing to discuss the types of things you brought up. He is extremely knowledgeable and probably the least biased (towards his product) than most.

Break-in of components and cables is a highly debatable subject and there just isn't a lot of systematic scientific evaluation but more anecdotal evidence gathered by end users. I am of the philosophy not all things we hear can necessarily be measured and plotted in a way that is in direct correlation to what/how we hear something.

Just because it does/doesn't show up on paper doesn't mean we did/didn't hear it that way.

See my sig...................it's what I believe.

H9

ben62670

Dennis Gardner wrote: »

It takes 300-400 hours to forget how many $$$ you blew in relation to the improvement in SQ.

Monetary memory is much stronger than auditory memory.;)

Hi Dennis:)

I have thought the same kind of mind tricks may have gone on. I am very skeptical, so I have purposely replaced caps in just one speaker, and not the other. Then did the second speaker at a later date. Their is a big difference with some caps. Depending on the cap they may take different amounts of time to burn in.

Ben

BTW
I have tested many of the caps I have pulled fom my speakers, and all but one were close to speck.

schwarcw

DarqueKnight's lack of a response (or two) is very compellling. Raife are you on the sideines chuckling?:) What happens to a capacitor when it burns in? Why does it take so long?

michaeljhsda2

......."then stop changing when they reached a point where they sounded the best." It's because the Caps and Resistors can read your mind via biochemical telepathic transference, and hence, know when it's time to stop changing. Duh. Great post OldmanSRS.