View Full Version : Electrolytic vs Polypropylene caps
I have been thinking of replacing some capacitors in my speakers crossover network.
Can anyone tell me if I should use poly caps rather than electrolytic and what the differences there may be in sound quality?
istari_knight
22-05-2014, 09:46
I'm fairly certain all Spendor speakers use film caps as standard... Can you post a picture ?
Replacements should ideally be done like for like due to the differences in equivalent series resistance (which with electrolytics varies with temperature and frequency so getting speakers voiced exactly the same with polys just isn't going to happen). However, as a general guide the following rule of thumb can be used:
Series resistance to add to polys if replacing electrolytics (approximate values):
ESR up to 200Hz = 1Ohm
ESR 200Hz to 500Hz = 0.7 Ohm
ESR 500Hz to 1500KHz = 0.5Ohm
ESR 1.5KHz upwards = 0.3Ohm
Don't forget this varies with temperature too and that may vary in itself on the specific rating of an individual electrolytic in a particular circuit position as well as with ambient temperature.
Advantages of electrolytics = cheap, compact for their rating and they provide some electrical damping that may be beneficial with some designs
Disadvantages = they tend to be less linear with frequency, the ESR varies with frequency and temperature, have higher dielectric absorption (memory); they can dry up and drift off tolerance over typically a 15 to 20 year period or sooner if used in higher current or temperature environments
Advantages of polys: Some are now specifically designed for crossover use, they're very linear, low in distortion, far less affected by temperature and have lower losses; have low dielectric absorption (cleaner sounding) and tend not to drift with age. they'll last the lifetime of the speaker or should.
Disadvantages: size, (comparatively) and cost.
Replacements should ideally be done like for like due to the differences in equivalent series resistance (which with electrolytics varies with temperature and frequency so getting speakers voiced exactly the same with polys just isn't going to happen). However, as a general guide the following rule of thumb can be used:
Series resistance to add to polys if replacing electrolytics (approximate values):
ESR up to 200Hz = 1Ohm
ESR 200Hz to 500Hz = 0.7 Ohm
ESR 500Hz to 1500KHz = 0.5Ohm
ESR 1.5KHz upwards = 0.3Ohm
Don't forget this varies with temperature too and that may vary in itself on the specific rating of an individual electrolytic in a particular circuit position as well as with ambient temperature.
Advantages of electrolytics = cheap, compact for their rating and they provide some electrical damping that may be beneficial with some designs
Disadvantages = they tend to be less linear with frequency, the ESR varies with frequency and temperature, have higher dielectric absorption (memory); they can dry up and drift off tolerance over typically a 15 to 20 year period or sooner if used in higher current or temperature environments
Advantages of polys: Some are now specifically designed for crossover use, they're very linear, low in distortion, far less affected by temperature and have lower losses; have low dielectric absorption (cleaner sounding) and tend not to drift with age. they'll last the lifetime of the speaker or should.
Disadvantages: size, (comparatively) and cost.
Thanks very much for that info Paul - I will proceed with caution as I would not want to change the sound of my speakers in any significant way.
Firebottle
22-05-2014, 13:04
James, having heard your SP2s, and having checked the tweeter caps I think you're chasing a bit of a dream.
They are great as they are :trust:
Alan
James, having heard your SP2s, and having checked the tweeter caps I think you're chasing a bit of a dream.
They are great as they are :trust:
Alan
Good advice
[QUOTE=Firebottle;553402]James, having heard your SP2s, and having checked the tweeter caps I think you're chasing a bit of a dream.
They are great as they are :trust:
Alan[/QUOTE
Just a bit nervous as they are so old, manufactured in 1986. Maybe best leave alone, as you can testify Alan they still sound fine. Any idea how long these components can last ?
CornishPasty
22-05-2014, 16:58
My IMFs are ten years older and have never been touched. Maybe a recap would improve them but they sound fine as they are so I'm leaving well alone. If it ain't broke........
walpurgis
22-05-2014, 18:00
My IMFs are ten years older and have never been touched. Maybe a recap would improve them but they sound fine as they are so I'm leaving well alone. If it ain't broke........
Dunno about a recap, but it may be an idea to check the values with a meter, just to be on the safe side.
Guys,
a word to the wise RE electrolytics and age: It really doesn't matter what a capacitance tester tells you because what it cannot measure is ESR. Electrolytics are cheap. If you have 'lytics older than say 15 to 20 years in your crossovers, change them out because some, like Alcaps, famously can have a huge increase in ESR with age through deterioration YET measure almost in tolerance for capacitance. This will screw up a speaker's response big time.
I have just had some lovely HB2s in for repair. Every cap in the crossover which was a 'lytic was within capacitance tolerance. All had massive equivalent series resistance to the point that the tweeters barely worked at all...(try 20dB down!). The chap thought he was in for a largish bill for new tweeters. The bill was a few quid for a handful of electrolytics.
They'll be good for at least another 15 years.
walpurgis
22-05-2014, 20:14
Hi Paul, didn't realise ESR could have such an impact. Is it a given that this will occur?
Hi Paul, didn't realise ESR could have such an impact. Is it a given that this will occur?
A can't say fdor sure with all caps Geoff, but every time I get anything old with "Alcap" written on it, they invariably are close enough on tolerance capacitance wise but are shot regarding ESR.
Basically it's not worth losing sleep over it as the cost of lytics is so low, and todays Alcap 'lytics are much better. More linear with frequency, but what they'd be like in 20 years, I can't say.
I don't even bother to measure them now as every one I've had in more than 20 years old has sounded a million dollars better once recapped. It's so relatively cheap just to bin old ones and do like for like replacements.
A chap from Germany was recently told by B&W not to touch his 30 yr old B&Ws as he'd screw them up and that the lytics would be fine. They were not sounding fine. I've just recapped the lot with like for like and they're now minty again. It cost relatively speaking peanuts.
I leave the MKTs and polys well alone even if they're not up to todays standards as that's what the speakers were voiced with and as long as they are within tolerance, they are generally fine and probably will be 30 years into the future. It also saves the clients hard earned cash. The way I look at it, if they sounded great when they were bought and have deteriorated since, 9 times out of 10, it's the 'lytics to blame and little else.
awkwardbydesign
22-05-2014, 21:00
Thanks very much for that info Paul - I will proceed with caution as I would not want to change the sound of my speakers in any significant way.
LOL! I remember someone asking me (about 35 years ago. Sheesh!) how to improve their stereo. When I asked what was wrong with the sound, they said "Nothing, I just want to improve it." I told them to leave it alone then, there is no end if you start!
I should have taken my own advice, but it was already too late for me! :(
walpurgis
22-05-2014, 21:12
LOL! I remember someone asking me (about 35 years ago. Sheesh!) how to improve their stereo. When I asked what was wrong with the sound, they said "Nothing, I just want to improve it." I told them to leave it alone then, there is no end if you start!
I should have taken my own advice, but it was already too late for me! :(
I know the feeling. Serves us both right I expect! :)
The caps fitted to the crossovers in the Original Spendor SP2,s are Ero.
The caps fitted to the crossovers in the Original Spendor SP2,s are Ero.
Now known as Vishay I believe. Great capacitors in their day, especially their polyester caps.
Now known as Vishay I believe. Great capacitors in their day, especially their polyester caps.
You have got me thinking Paul as I looked up some Ero caps that were similar to mine and they were ploys, is it possible mine are and not electrolitics? Speakers were manufactured in 1986.
brucew268
23-05-2014, 16:40
Thank you Paul for your wisdom on the subject of crossover electrolytics, espec Alcaps. Ive been reading with interest, as I have the same in the crossovers I'm getting ready to muck with.
anthonyTD
23-05-2014, 16:49
:)
A can't say fdor sure with all caps Geoff, but every time I get anything old with "Alcap" written on it, they invariably are close enough on tolerance capacitance wise but are shot regarding ESR.
Basically it's not worth losing sleep over it as the cost of lytics is so low, and todays Alcap 'lytics are much better. More linear with frequency, but what they'd be like in 20 years, I can't say.
I don't even bother to measure them now as every one I've had in more than 20 years old has sounded a million dollars better once recapped. It's so relatively cheap just to bin old ones and do like for like replacements.
A chap from Germany was recently told by B&W not to touch his 30 yr old B&Ws as he'd screw them up and that the lytics would be fine. They were not sounding fine. I've just recapped the lot with like for like and they're now minty again. It cost relatively speaking peanuts.
I leave the MKTs and polys well alone even if they're not up to todays standards as that's what the speakers were voiced with and as long as they are within tolerance, they are generally fine and probably will be 30 years into the future. It also saves the clients hard earned cash. The way I look at it, if they sounded great when they were bought and have deteriorated since, 9 times out of 10, it's the 'lytics to blame and little else.
awkwardbydesign
23-05-2014, 17:38
You have got me thinking Paul as I looked up some Ero caps that were similar to mine and they were ploys, is it possible mine are and not electrolitics? Speakers were manufactured in 1986.
Bi-polar electrolytics in speakers frequently look like one of these types- black plastic, or double ended metal. They could be different, but if you have either of these types then they will be electrolytics.
http://p.globalsources.com/IMAGES/PDT/B1051852086/Aluminum-Electrolytic-Capacitor.jpg
http://thumbs3.ebaystatic.com/d/l225/m/mbX1RJfSFDR3K-N16YCxHJg.jpg
Hi Richard, mine look like thesehttp://www.geocities.ws/overmindxx/pictures/Film_or_Ceramic/ERO_MKT1822_1uF_250V.jpg
brucew268
23-05-2014, 18:14
Look like film to me.
istari_knight
23-05-2014, 19:10
See post #2 ;)
I'm fairly certain all Spendor speakers use film caps as standard... Can you post a picture ?
Ahh yes James - I eventually got round to it.:lol:
Hi Richard, mine look like thesehttp://www.geocities.ws/overmindxx/pictures/Film_or_Ceramic/ERO_MKT1822_1uF_250V.jpg
They should be fine left well alone. They look like Ero MKT metallised polyester film caps to me.
awkwardbydesign
23-05-2014, 21:06
Hi Richard, mine look like thesehttp://www.geocities.ws/overmindxx/pictures/Film_or_Ceramic/ERO_MKT1822_1uF_250V.jpg
MKT= polyester. K=10% tolerance. Datasheet- http://www.vishay.com/docs/26012/mkt1822.pdf x2 usually means mains rated for suppression duty, but on this datasheet x appears to be a multiplier, so I wouldn't use on mains voltage. Suppression caps are usually metallised polypropylene too. Fine for crossovers.
Polyprops are usually preferred to polyesters, but a good polyester is better than a poor polyprop. These should be fine. Unless you want to go crazy and try Teflon or PIO. But I wouldn't advise it.
PS. I don't take my own advice
http://i.ebayimg.com/t/1x-RARE-10uF-200V-5-PIO-Capacitors-KBG-/00/s/NDk2WDYyMg==/$(KGrHqVHJEQF!d)u3e3PBQ,,tCy,bQ~~60_3.JPG
brucew268
24-05-2014, 08:14
Those just look dangerous! I'd be waiting for some nasty chemical to come leaking out of them. ;)
MKT= polyester. K=10% tolerance. Datasheet- http://www.vishay.com/docs/26012/mkt1822.pdf x2 usually means mains rated for suppression duty, but on this datasheet x appears to be a multiplier, so I wouldn't use on mains voltage. Suppression caps are usually metallised polypropylene too. Fine for crossovers.
Polyprops are usually preferred to polyesters, but a good polyester is better than a poor polyprop. These should be fine. Unless you want to go crazy and try Teflon or PIO. But I wouldn't advise it.
PS. I don't take my own advice
http://i.ebayimg.com/t/1x-RARE-10uF-200V-5-PIO-Capacitors-KBG-/00/s/NDk2WDYyMg==/$(KGrHqVHJEQF!d)u3e3PBQ,,tCy,bQ~~60_3.JPG
awkwardbydesign
24-05-2014, 08:16
Those just look dangerous! I'd be waiting for some nasty chemical to come leaking out of them. ;)
Nah, just radioactive. :eek:
anthonyTD
24-05-2014, 09:39
I still have quite a few of these types kicking about, mainly Aerovox, probably full of nasty oil containing PCB's...saying that, they probably sound great in cross-overs, but i wouldn't advise using them as coupling caps in a valve circuit! :eek:
Those just look dangerous! I'd be waiting for some nasty chemical to come leaking out of them. ;)
brucew268
24-05-2014, 12:26
a word to the wise RE electrolytics and age: It really doesn't matter what a capacitance tester tells you because what it cannot measure is ESR. Electrolytics are cheap. If you have 'lytics older than say 15 to 20 years in your crossovers, change them out because some, like Alcaps, famously can have a huge increase in ESR with age through deterioration YET measure almost in tolerance for capacitance. This will screw up a speaker's response big time.
Paul's experiences with Alcaps electrolytics started me thinking about my Proac 1SC which have to be getting close to 20 years. I got them second hand and put them into active use in 2007, soon noticing that I wasn't getting much detail up top and the lack of detail made the sound feel sluggish. I put it down to the smooth creamy nature of the Solen polypropylenes and replaced them with Ansar polys, which improved things a good bit. Now I'm wondering if the problem possibly never as the Solen caps but the Alcaps electroytic. If so, the Ansar would actually be compensating for the Alcaps rather than replacing the failings of the Solens. Reality is likely more complicated. So replace the Alcaps with Silmic. Have a listen. Consider putting the Solens back into action. Have another listen. If that doesn't satisfy, roll to another cap I've been eyeing. Or spend the next 8 months preparing the ground with my wife for a new set of (probably old) speakers.
Hmm. More experimentation... can't possibly do all this meaningfully in 1 weekend, or even 2. :scratch:
awkwardbydesign
24-05-2014, 16:15
I still have quite a few of these types kicking about, mainly Aerovox, probably full of nasty oil containing PCB's...saying that, they probably sound great in cross-overs, but i wouldn't advise using them as coupling caps in a valve circuit! :eek:
If the voltage margin is adequate, why wouldn't you? (I just like to learn)
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