Capacitor Myths

[Carlspeak]

Those black with red end caps are on my 'bad/ugly' list. Most of those I have tested yielded very poor result vs specs. I'm not sure exactly what they are but I do have an opinion the most of them were made by the same contract cap manufacturer and labeled to suit whomever placed a large order for use in their speaker line/s. Visit my cap thread 'the good, the bad and the ugly'. I provide some test results and a list of brand names these bad boys have.

[DavidR]

I've read it Carl and I very much like how you always back-up your position with factual testing.

[Pete B]

I would not worry at all about ESR in a speaker like that AR-3a that has level pots

on the mid and tweeter, the slightest tick down on the pots will adjust for the difference.

Plus the drivers are so old, who knows if they are in spec.

[harry398]

10 hours ago, Carlspeak said:

What is even more confusing and harder to understand are people's audio preferences which can vary quite widely. You say your AR3a sounds nice and many other owners would probably say don't change a thing because you will alter the 'original voicing'. Replacing old electrolytic caps with new  PP film types will most likely alter the voicing somewhat because you removed the low level series resistance (called ESR) the lytics provided and replaced it with virtually no series resistance. Thus with a voltage boost to the mids and tweets, you will hear things more 'clearly'. 

Some recappers who are paranoid about altering the original voicing will add a low value 1/4 ohm or so resistor in series with the new film cap to maintain that low level ESR. 

A lot depends on how badly the factory lytics aged and their ESR increased which is the unknown to the casual one-time recapper. If an old lytic's ESR has risen well over 1 ohm which can happen in come cases, a change to a film cap with 0.1 ohm ESR will most likely result in the re-capper complaining about the sound being too bright. Although, I often wonder about those with rheostats or L-pads on their speakers should be able to compensate by turning them down a bit (i.e. adding in some series resistance). 

So Harry, I suggest you read up on ESR and it's relationship to re-capping outcomes. There's a mountain of information on the subject on the WWW. 

BTW, if you are lucky, your AR3a's might have Sprague Compulytic caps in them - in which case you won't need to recap them because numerous tests I've done on that make and brand have shown little or no drifting of ESR with age. 

 

Carl,

1.  the ar3a has the paper brick style capacitor inside.

I was very happy and still am happy with the tones and sounds the ar3a produces.   They are in my top 3 speakers.

However, The recapping of the ar5 brought a comparison directly to the ar3a.  No the ar5 did not make it into my top 3, but they are much clearer now.    I would like to bring that to the ar3a.   The issue I have with recapping them...is that I am forced to do all of the caps, since that paper cap has the mid and woofer cap in one. 

so here is a question, the cheap film caps are worse, equal, or superior to the original?   Do I need to shell out 60  a cap for the woofer?  

I have leftover polys so I have the smaller ones in stock, never bought the 150mf, since 120 bux makes me think harder about the experiment.

To answer your point on "original voicing"  it not about the volume output of the drivers on the ar3a....its after a comparison with the ar5 i notice how clear the midrange can be.

The ar 50 schematic recommends non polarized electrolytics on the 70-160-450mf.......and the others are 100v metallized polyester film type.   I own a set of those and find it interesting they recommend the cheaper caps on large sizes.......

btw...I found the ar50 schematic in here....

 

http://www.classicspeakerpages.net/library/acoustic_research/special_sections/drawings/SpeakerDrawings.swf

Thanks for the input

Harry

[harry398]

9 hours ago, DavidR said:

Harry,

What Carl says is the reason for the difference IMO. I have a pair of AR91's recapped with Dayton polys. The result was clear, detailed sound. I hesitate to use the word 'bright' as it carries a different meaning for me. I also have a pair or AR90s which have all the original caps and resistors. I swap them out from time to time. I have never listened to them back-to-back. In other words I've never listened to one pair and immediately started using the other UNTIL the other day. I put the 90's in place and began listening immediately............the HORROR...................they sounded dull and lifeless. The only thing that was better was the bass. I have little to no doubt if I replaced all the caps with some new, quality electrolytics they too would sound just as good as the 91s with poly caps. The only difference/drawback is the electrolytics will drift (again) over time and the polys will stay the same.

Hello David,

 

so you think the electrolytics are ok, but their service life is limited?   Is that what I am to understand?

 

[harry398]

I have uploaded a pic of My ar98ls crossover.

The factory caps.....electrolytics?   or poly?

 

unicon bi-polar.    

 

 

[Carlspeak]

50 minutes ago, harry398 said:

I have uploaded a pic of My ar98ls crossover.

The factory caps.....electrolytics?   or poly?

 

unicon bi-polar.    

 

 

They are all electrolytics. Easy to tell by the beer can shape. 

[Carlspeak]

1 hour ago, harry398 said:

 

Carl,

1.  the ar3a has the paper brick style capacitor inside.

I was very happy and still am happy with the tones and sounds the ar3a produces.   They are in my top 3 speakers.

However, The recapping of the ar5 brought a comparison directly to the ar3a.  No the ar5 did not make it into my top 3, but they are much clearer now.    I would like to bring that to the ar3a.   The issue I have with recapping them...is that I am forced to do all of the caps, since that paper cap has the mid and woofer cap in one. 

so here is a question, the cheap film caps are worse, equal, or superior to the original?   Do I need to shell out 60  a cap for the woofer?  

I have leftover polys so I have the smaller ones in stock, never bought the 150mf, since 120 bux makes me think harder about the experiment.

To answer your point on "original voicing"  it not about the volume output of the drivers on the ar3a....its after a comparison with the ar5 i notice how clear the midrange can be.

The ar 50 schematic recommends non polarized electrolytics on the 70-160-450mf.......and the others are 100v metallized polyester film type.   I own a set of those and find it interesting they recommend the cheaper caps on large sizes.......

btw...I found the ar50 schematic in here....

 

http://www.classicspeakerpages.net/library/acoustic_research/special_sections/drawings/SpeakerDrawings.swf

Thanks for the input

Harry

When I restored many 3a's, I usually replaced those large paper/wax bricks with Erse 150 and 50 uF electrolytics. I added Dayton 0.1 uF film/foil bypass caps to each lytic. They will last you another 30-40 years, So, I wouldn't be too concerned about service life. Their sonic performance will equal the OEM parts. Replace the 6 uF paper/wax cap with a film cap. MPP is a good choice. Get whatever your budget can handle. 

[harry398]

unsure what this is. and how you did it......   I added Dayton 0.1 uF film/foil bypass caps to each lytic

 

yes....i am feeling better about the electrolytics now....Thank you Carl.     

[DavidR]

@harry398

It looks as if Carl has answered your questions.

[AR surround]

Myth or Fact:  Replacing a capacitor with two or more in parallel can potentially have adverse affects on speaker performance?

I got into this discussion with a colleague regarding the replacement of the 350uF cap in the AR90.   We all know that it is often difficult to find a single replacement capacitor with an identical value as well as acceptable audio grade quality.   So a typical solution has been to use two or more caps in parallel.   The concerns discussed were:

- ESR and Reactance (Xc) change with frequency.  If the two caps used in parallel have different curves, how might this affect speaker performance?

- Polyprops have very low ESR.   The problem is that the polyprops are very expensive in the larger sizes...about $100 to $150 to replace the 350uF in each AR90 with two caps in parallel.   Have people used two non-polarized electrolytics in parallel and achieved acceptable audio results?

- Discharge rates: If the two caps are not perfectly matched, there is a possibility that they will have different discharge rates and one could discharge into the other.   How might this affect performance?

- Is it better to use two caps of the same value (i.e. 2 x 175uF to replace the 350uF cap in the AR90) then to replace it with two of different values (i.e. one 250uF and one 100uF)?

Your experiences and thoughts would be appreciated.

[Carlspeak]

4 minutes ago, AR surround said:

Myth or Fact:  Replacing a capacitor with two or more in parallel can potentially have adverse affects on speaker performance?

I got into this discussion with a colleague regarding the replacement of the 350uF cap in the AR90.   We all know that it is often difficult to find a single replacement capacitor with an identical value as well as acceptable audio grade quality.   So a typical solution has been to use two or more caps in parallel.   The concerns discussed were:

- ESR and Reactance (Xc) change with frequency.  If the two caps used in parallel have different curves, how might this affect speaker performance?

- Polyprops have very low ESR.   The problem is that the polyprops are very expensive in the larger sizes...about $100 to $150 to replace the 350uF in each AR90 with two caps in parallel.   Have people used two non-polarized electrolytics in parallel and achieved acceptable audio results?

- Discharge rates: If the two caps are not perfectly matched, there is a possibility that they will have different discharge rates and one could discharge into the other.   How might this affect performance?

- Is it better to use two caps of the same value (i.e. 2 x 175uF to replace the 350uF cap in the AR90) then to replace it with two of different values (i.e. one 250uF and one 100uF)?

Your experiences and thoughts would be appreciated.

The general answer to all of your questions is negligible affect on performance. IIRC, the 350 uF cap and in the AR90 is in the low pass circuit which is by definition less critical than the midrange or tweeter circuits.  If you could see some of the cap bundles great speaker designers like Peter Snell used you'd be shocked. 

Most modern audio bi-polar lytics have reasonably tight tolerances (<= 5% D.F.) so exact matching for bass circuit use is, to me, a waste of time.

The answer to your last question is yes and yes. 

 

[JKent]

Myth.

In fact, some audiophiles advocate the use of "bypass" caps (adding a small value high quality film cap in parallel) or even "cascading" caps (using more than 2 caps of decreasing values) to improve the sound. And I'll admit to having done that from time to time. But it's snake oil.

-Kent

[Carlspeak]

I have to confess as well Kent. I think JBL are the ones who started the practice. The infamous Zilch (R.I.P.) was also an advocate of bypassing NPE's with low value film/foil caps. In fact North Creek Audio made a business out of cascading and sold a lot of caps in the process. 

Snake oil? The web is rife with arguments about this. They usually boil down to the subjectivists (believers) vs the objectivists (non-believing engineers).

 

[JKent]

Yes, you can really go down a rabbit hole with this one. And I kind of veered off from the question: Does it do any harm? (no)

I think all of us here have used caps in parallel to make values that were either unavailable or too expensive. Not too long ago Madisound had a great deal on "surplus" 10uF film caps for 60 cents each (or even 50 cents if you bought a lot of them). Many of us used those to make bigger values. For example, a 50uF Dayton film cap is $15. but 5 surplus caps could cost $2.50.

When I restored my Cizek KA-1s I did not cut corners--they are beautiful and rare speakers--but I had no hesitation using a bunch of 10uF surplus caps, along with some other smaller values, to "build" the numerous 20uF and 25uF caps needed. The savings was significant. Cizek crossovers are very complex. On this xo there are 3 25uF, 3 20uF and 1 10uF. Using 5% Daytons would have cost about $50 per xo. The 13 10uF caps and 2 Carli 4.7uF caps came to $8 per xo.

-Kent

[GlennW]

Those capacitors look familiar.  I made similar construction for AR3a capacitor replacement. 

The Madisound 10uF surplus capacitors are gone now, they will be missed.

[DavidR]

Parallel madness

 

[stupidhead]

25 minutes ago, DavidR said:

Parallel madness

 

nice work David!

[AR surround]

Thanks to each of you for your replies.   What I deduce from the photos, and in Carlspeak's response to one of the questions, is that most of you have used banks of identical capacitors.   So if one were to replace the 350uF cap in the AR90, a bank of seven (7) 50uF NPEs would be preferable to a combo of a 200uF and a 150uF NPE.   Seven 50uF NPE's from Parts Express would run about $8...dirt cheap.

[JKent]

9 minutes ago, AR surround said:

What I deduce from the photos, and in Carlspeak's response to one of the questions, is that most of you have used banks of identical capacitors. 

I don't want to contradict Carl and would be happy to know his reasoning but no--I don't believe there is a sonic or electrical advantage to using identical caps. To make up a 350uF I'd probably use a 200 and a 150, or even a 330 and a 20. Or a 330 and two of those surplus 10s. You can mix NPE and film. Also, you want to be sure that all caps in your bundle are at least equal to the voltage rating of the original, but it's OK to mix voltages. People who like to use bypass caps may, for example, might use a 0.01uF 630v cap in parallel with a 10uF 100v cap.

I see no advantage to bundling 7 50uF caps. It would be a bit cumbersome.

YMMV.

[Pete B]

There is actually a good reason to parallel modern cheap NP electrolytics,

when replacing the large can Spragues.  Most of those old large can types 

are constructed in a way where the terminals attach to multiple points on 

the plate foil which by design lowers the ESR and ESL.  Most crossover NPEs

have only one attachment point, so if you use 5 lower value caps the foil wind

is shorter and you are roughly simulating multiple attachment points.  The ESR

and ESL is then 1/5 of the individual values for the single caps.

[Carlspeak]

1 hour ago, JKent said:

I don't want to contradict Carl and would be happy to know his reasoning but no--I don't believe there is a sonic or electrical advantage to using identical caps. To make up a 350uF I'd probably use a 200 and a 150, or even a 330 and a 20. Or a 330 and two of those surplus 10s. You can mix NPE and film. Also, you want to be sure that all caps in your bundle are at least equal to the voltage rating of the original, but it's OK to mix voltages. People who like to use bypass caps may, for example, might use a 0.01uF 630v cap in parallel with a 10uF 100v cap.

I see no advantage to bundling 7 50uF caps. It would be a bit cumbersome.

YMMV.

I agree with Kent and feel the use of multiple caps of the same value was driven more by economics - the 10 uF caps being available and very cheap and film instead of lytic for those who have a bias against lytics. 

I mentioned Peter Snell before. You should see his bundles of 4 uF lytics in the Model A! I guess he bought thousands of them and paralleled as many as he needed to get the total he wanted. In the case of the Model A he also added a flat profile drop shaped cap for gluing the bundle to the crossover board.

Below is a picture of a Model A bundle. It's been lifted away from the small film drop shaped cap peeking out from below the glob of glue.

 

[DavidR]

1 hour ago, stupidhead said:

nice work David!

Thanks, but NOT my handy work.

[DavidR]

1 hour ago, AR surround said:

Thanks to each of you for your replies.   What I deduce from the photos, and in Carlspeak's response to one of the questions, is that most of you have used banks of identical capacitors.   So if one were to replace the 350uF cap in the AR90, a bank of seven (7) 50uF NPEs would be preferable to a combo of a 200uF and a 150uF NPE.   Seven 50uF NPE's from Parts Express would run about $8...dirt cheap.

I'm planning on using 400V Solen 200uF + 150uF poly caps in my 90s IF the originals are out of spec.

[DavidR]

On the issue of bypassing and cascading: I know North Creek was known for this (they just closed up shop about a  month ago). They always chose a bypass that had higher voltage rating than the base cap and when cascading each successive bypass was of a higher voltage rating and smaller capacitance value. I don't know the purpose of this.

I've also read on Tony Gee's site for cap evaluations (ughhh) that he recommends a Vishay 1837 0.01uF (10nF) cap for a bypass to 'smooth out' and 'improve' the SQ of the base cap. This cap is (I think) rated for 100VAC and 160VDC. I'm not sure of this but wouldn't that make the base cap a 100VAC cap as well? In other words if the base cap was a 400VDC cap by putting that small cap on as a bypass make the base cap the lower of the two ratings?