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Old 13th October 2012, 06:16 PM   #1
tomst is offline tomst  United Kingdom
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Default how to use capacitors

Ok this has probably asked a million times but i can't seam to find any real answers to what I'm asking.
I acquired some leak sandwich speakers (mini and 2way) they still have what looks like the original bipolar electrolytic capacitors that must be getting on for 40 years old now. I understand that replacing them with film caps will do them no end of favours. I also have an stereo 70 amp, in need of a rebuild, that has high value speaker coupling capacitors standard are 2200f but can, i believe, be pushed to about 4700f. questions are.

1. Speakers:
The cap in parallel with the woofer does it need to be a really good poly type?
The tweeter cap as it is directly in the signal path it should be a very good poly cap?
I understand the multiple caps paralleled are better?
The woofer inductor in the 2way are bypassed with a large carbon comp 22 Ohm resistor then a 1f capacitor. Reading from left to right on the positive line: supply-inductor-woofer.
does this need to be a poly type cap and does the resistor need changing.

2. Amp:
What should i be using to couple the speakers. At the moment it has polarised electrolytics in it. i believe that in this place theoretically i should have a film cap but that wold be massive.

3. what is the right way of paralleling capacitors to get the value you want. If i can get two/three/four values the same to add up to what I want then good. But what if I can't and i have to use say one smaller value and one larger value. I only ask because i read somewhere that if the values are different but too close then it wont work as well. can't find it now.
Finally should i be bypassing any of these caps with ?% smaller film caps.

Thanks
Tom
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Old 13th October 2012, 06:41 PM   #2
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Replace, replace, replace !
It's the electrolyte that dries ...some say ! I'm using some bipolars from the '70s too,
and they're still fine ! Different is the output coupling cap of the amp ,which has to be perfect . A good industrial type aluminum I think is best ( like the old ones on some Philips amps );replace also the supply cap and all the old ones ; probably you'll hear a different sound , more richer in the bass .
For the cap on the tweeter , go for 250 V or higher . But you could surprisingly find that
a 50 cent bipolar suits to your taste ( IMHO !!!)
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Old 13th October 2012, 07:44 PM   #3
xjr100 is offline xjr100  Europe
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Quote:
Originally Posted by tomst View Post
1. Speakers:
The cap in parallel with the woofer does it need to be a really good poly type?
The tweeter cap as it is directly in the signal path it should be a very good poly cap?
I understand the multiple caps paralleled are better?
The woofer inductor in the 2way are bypassed with a large carbon comp 22 Ohm resistor then a 1f capacitor. Reading from left to right on the positive line: supply-inductor-woofer.
does this need to be a poly type cap and does the resistor need changing.
Tom, everything depends on exact speaker model. Generally, replacing electrolytics to poly will bring the improvements, but if speaker response is not flat enough, replacing electrolytic in mids-highs with poly-type capacitors can make sound more exact, without smoothing, but can highlite, for example peak and make your high-mids very unpleasant. So, you need to do some corrections in crossover to change speaker response. Same job as engineering speakers (proper equipment, software, etc.). Same with bass: it can be more exact with poly, but you can loose some "volume" - sound can be a bit "dry".
There is no exact answer - yes or no, you need to try.
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Old 13th October 2012, 08:57 PM   #4
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Place a Solen across your woofers, and some CrossCaps, ClarityPX, or Erse PulseX caps for starters on the tweeter.
I'd use a CrossCap for the 1uF in that notch on the woofer.

The large 'Lytics in an amp should be okay.

All components are in the signal path, series or parallel, so that archaic thought process is incorrect.

Later,
Wolf
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Last edited by wolf_teeth; 13th October 2012 at 08:59 PM.
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Old 13th October 2012, 09:28 PM   #5
tvrgeek is offline tvrgeek  United States
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The spec for electros is about 7 years. Usually, unless abused by high current or high temp, about 10 years is their life. Poly caps will be much closer to the designed spec. 5% or better, where electro's are 20% on a good day, 50% on a bad. That can be a large part of the sound change when caps in filters are changed.

The difference between an electro and a mylar is big. A small step to poly-pro. Tiny improvement to exotic, tight wrapped audio caps. Let your wallet be your guide. I use the 1% Daytons.

In the amp, yes, you can put in larger main caps and lower ESR. If you do, you should really think about a larger rectifier. The change to a hexfred rectifier and larger low ESR caps made a very large and measurable difference in my DH-120. Over 8 dB lower noise floor.
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Old 13th October 2012, 09:33 PM   #6
cbdb is offline cbdb  Canada
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Quote:
All components are in the signal path, series or parallel, so that archaic thought process is incorrect.
Sorry, learn some electronics before you spout anymore nonsense.
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Old 13th October 2012, 09:42 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by tomst View Post
1. Speakers:
The cap in parallel with the woofer does it need to be a really good poly type?
The tweeter cap as it is directly in the signal path it should be a very good poly cap?
I understand the multiple caps paralleled are better?
The woofer inductor in the 2way are bypassed with a large carbon comp 22 Ohm resistor then a 1f capacitor. Reading from left to right on the positive line: supply-inductor-woofer.
does this need to be a poly type cap and does the resistor need changing.

2. Amp:
What should i be using to couple the speakers. At the moment it has polarised electrolytics in it. i believe that in this place theoretically i should have a film cap but that wold be massive.

3. what is the right way of paralleling capacitors to get the value you want. If i can get two/three/four values the same to add up to what I want then good. But what if I can't and i have to use say one smaller value and one larger value. I only ask because i read somewhere that if the values are different but too close then it wont work as well. can't find it now.
Finally should i be bypassing any of these caps with ?% smaller film caps.

Thanks
Tom
Hi,

1a) No. A bipolar electrolytic will be fine.

1b) Standard poly type will be well good enough.

1c) Sometimes. It doesn't hurt.

1d) No and no, though 1uF is cheap anyway that you do it.

2) A polar electrolytic bypassed by a much smaller similar or poly.
(In fact replace all electrolytics in the amplifier, doubling the values
of all supply, coupling and decoupling capacitors, new ones will fit.)

3) Make up the parallel total any way you like, don't be too precious.

The Leaks don't need flash capacitors. Just ones that work properly.
New bipolar electrolytics will make far more difference than upgrading
those to basic or flashy film types paralleled or not.
My friend has an original pair. Not worth boutique components IMHO.

rgds, sreten.

http://www.falconacoustics.co.uk/
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Last edited by sreten; 13th October 2012 at 09:49 PM.
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Old 14th October 2012, 06:35 AM   #8
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Quote:
Originally Posted by cbdb View Post
Sorry, learn some electronics before you spout anymore nonsense.
Sounds like you require a refresher yourself. If the components in shunts don't make any difference, then notches, zobels and such wouldn't be used.

It all matters.

Later,
Wolf
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Old 14th October 2012, 10:05 AM   #9
sreten is offline sreten  United Kingdom
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Hi,

It is pretty clear what is meant by "in the signalpath" and "not in the signalpath"
and nitpicking doesn't really help the situation, or promote understanding.

rgds, sreten.
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Old 14th October 2012, 12:34 PM   #10
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One thing that is often overlooked when thinking about replacing electrolytics with film caps is the fact that the ESR of the caps will likely be quite different (with electros generally having much higher ESR).

Depending on the crossover, the esr in the electros may in fact be adding some damping that won't be there with the film caps, leading potentially to some peaking when film caps are substituted. The other place where electros vs films seems to make a big difference is in notch filters, with my experience being that electros of the same value as films in the same notch give quite different results.

In a lot of cases it shouldn't matter, but it doesn't mean that in all cases it won't matter

Tony.
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