Hi all,...
Example....1.5uf 50V x 4=6uf 200v.....1x6uf 400v= correct uF...but not sure about extra 200V on caps....L.L (Low Leakage)........mite put my 66's in the wheely bin.....
The example given here is quite wrong and ultimately dangerous. and I don't mean to be rude here, but if you don't understand what I am about to write, you probably shouldn't be attempting this:
If you have 4 x 1.5uF caps, used in series they can, maybe, regarded as having a 200v rating, but they will collectively only have a 0.375uF value.
The 200v rating relies on the values being exactly matched so the voltage drop across all the caps while they are working is the same, your mileage may vary. Personally I'd not do it with any speakers (or amplifiers) I cared about.
Caps in parallel 'add' their values together, but they do not achieve higher voltage rating, in fact the rating drops to the value of the lowest. So paralleling 4 x 1.5u/50v caps gives you a 6.0uF cap with a 50v rating.
Once again if you don't know the difference between serial and parallel connections of components you are out of your depth and at best will end up with something that sounds awful, or at worst bursts into flames.
HTH
Stuart
Thanks for advice......not attempted yet...but just reviewing the situation....but even though you have stated that my calculatios are incorrect...could you please tell me the correct way to achieve my gold.....repairing my crossover.....hopefully i will find a new tweeter.pair
Thanks
P.T.R.D
Thanks
P.T.R.D
The picture you posted was very clear, in terms of the components shown, but can you give me a hand with the wires?
Looks to me like the round black disk with the pair of terminals is the input cup...
Then there is a pair headed upwards, to the tweeter?
There are two pairs headed off to the left, so I assume there is a pair of woofers?
One quick test, get a small, but full-range (not tweeter) speaker, then play music at a level you can clearly hear through the FR, reconnect the wires to the ditton, and make sure you hear the music at the back of the input terminals, just as when the FR is connected directly to the amp, then move to test at the end of the wires at the entry to the crossover boards.
Obviously if you can't hear the input clearly here, there are but two options, either the crossover is not to blame, the input wires are defective, or it's a dead short...
I'm going to look around and see if I can find an' official' schematic of the crossover.
Stuart
Looks to me like the round black disk with the pair of terminals is the input cup...
Then there is a pair headed upwards, to the tweeter?
There are two pairs headed off to the left, so I assume there is a pair of woofers?
One quick test, get a small, but full-range (not tweeter) speaker, then play music at a level you can clearly hear through the FR, reconnect the wires to the ditton, and make sure you hear the music at the back of the input terminals, just as when the FR is connected directly to the amp, then move to test at the end of the wires at the entry to the crossover boards.
Obviously if you can't hear the input clearly here, there are but two options, either the crossover is not to blame, the input wires are defective, or it's a dead short...
I'm going to look around and see if I can find an' official' schematic of the crossover.
Stuart
and to answer the other question you posed...
You can definitely replace the components with modern correctly rated parts. Whether the result will sound different to the original is hard or probably impossible for me, you or anyone else to judge, since even a perfectly functional ditton 44 from that era will have components whose values have become quite different over the years, and (IMHO) nobody should trust audio memory from a different decade.
Given they are presently completely non-functional, getting the correct nominal values in a working crossover will give you an infinite improvement, and likely be as good or better than original. Obviously you can tune things once you achieve functionality, since virtually none of the moving parts will be within original spec, magnets lose strength, spiders stiffen or loosen, surrounds sag a little etc.
As other posters have mentioned, it's hard to imagine the coils are defective as long as they are still connected properly. Assuming no inductance tester, you can test this with a multi-meter, simply un-solder one end and then measure the resistance of the coil. It should be some quite low number of ohms or may simply look like a short circuit. Re-solder the end when you are done testing. It may sound silly, but basic metal fatigue can make connections flaky after many years of vibrating.
Assuming you can determine the values of the resistors from looking at them, unsolder one end and measure to ensure they are within a few percent of the nominal value.
With respect to the caps: the values you need are pretty easy to figure out, simply add up the paralleled caps. But as you are aware, these may not be available in a single exact match. The easiest way to make the final value is simply to parallel caps with the correct voltage to add up to the correct value.
I'd not be spending any large amount of money getting high end caps until you'd had some audition time with the original values in place, then you will have a chance to tune a bit and then spend the money where it does you the most good, better tweeter and mid caps. I find it hard to believe it's critical in the bass, since the caps there are 'subtractive'.
HTH
Stuart
You can definitely replace the components with modern correctly rated parts. Whether the result will sound different to the original is hard or probably impossible for me, you or anyone else to judge, since even a perfectly functional ditton 44 from that era will have components whose values have become quite different over the years, and (IMHO) nobody should trust audio memory from a different decade.
Given they are presently completely non-functional, getting the correct nominal values in a working crossover will give you an infinite improvement, and likely be as good or better than original. Obviously you can tune things once you achieve functionality, since virtually none of the moving parts will be within original spec, magnets lose strength, spiders stiffen or loosen, surrounds sag a little etc.
As other posters have mentioned, it's hard to imagine the coils are defective as long as they are still connected properly. Assuming no inductance tester, you can test this with a multi-meter, simply un-solder one end and then measure the resistance of the coil. It should be some quite low number of ohms or may simply look like a short circuit. Re-solder the end when you are done testing. It may sound silly, but basic metal fatigue can make connections flaky after many years of vibrating.
Assuming you can determine the values of the resistors from looking at them, unsolder one end and measure to ensure they are within a few percent of the nominal value.
With respect to the caps: the values you need are pretty easy to figure out, simply add up the paralleled caps. But as you are aware, these may not be available in a single exact match. The easiest way to make the final value is simply to parallel caps with the correct voltage to add up to the correct value.
I'd not be spending any large amount of money getting high end caps until you'd had some audition time with the original values in place, then you will have a chance to tune a bit and then spend the money where it does you the most good, better tweeter and mid caps. I find it hard to believe it's critical in the bass, since the caps there are 'subtractive'.
HTH
Stuart
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Capacitors' internal circuits
Hi Stuart,
-{and P.T.R.D. - do read this }-,
No capacitor is actually a pure Capacitance only, though some types, including the modern Polypropylene types,
are very close to pure capacitance in the frequency bands they are designed and manufactured for.
Even a simplified internal circuit of a capacitor would contain :-
three capacitors + three resistors + one inductor.
All these are significantly present in Electrolytic caps,
and to somewhat lesser degree in Mylar caps.
The effects of all these internals are audible, and only two of them are useful for cross-overs' applications -
- the rated Capacitance and the Equivalent Series Resistance -{ESR}.
Thus when one changes from electrolytics to polypropylenes,
an equivalent resistance to the ESR of the electro may have to be added in electrical Series
with the polyprop cap for the cross-over to continue to work in the way the original designer intended.
Even with polypropylene caps, there are differences made to the Transient Response of the audio signal
when polyprop caps with different internal plates' widths are connected in Parallel.
To retain the original transient response one should connect only caps of the same internal plates' widths in parallel.
Usually Axial type poly caps of the same body length have the same internal plates' width, at least when from the same Manufacturer.
For Radial type caps, the plate width is usually equal to the distance between the connecting leads.
Hi Stuart,
-{and P.T.R.D. - do read this }-,
No capacitor is actually a pure Capacitance only, though some types, including the modern Polypropylene types,
are very close to pure capacitance in the frequency bands they are designed and manufactured for.
Even a simplified internal circuit of a capacitor would contain :-
three capacitors + three resistors + one inductor.
All these are significantly present in Electrolytic caps,
and to somewhat lesser degree in Mylar caps.
The effects of all these internals are audible, and only two of them are useful for cross-overs' applications -
- the rated Capacitance and the Equivalent Series Resistance -{ESR}.
Thus when one changes from electrolytics to polypropylenes,
an equivalent resistance to the ESR of the electro may have to be added in electrical Series
with the polyprop cap for the cross-over to continue to work in the way the original designer intended.
Even with polypropylene caps, there are differences made to the Transient Response of the audio signal
when polyprop caps with different internal plates' widths are connected in Parallel.
To retain the original transient response one should connect only caps of the same internal plates' widths in parallel.
Usually Axial type poly caps of the same body length have the same internal plates' width, at least when from the same Manufacturer.
For Radial type caps, the plate width is usually equal to the distance between the connecting leads.
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Hi Alan, Tinitus et al,
If I find out the crossover points for the 3 drivers from Celestion, would making or even buying new crossovers be a simple matter, or complex? I ask because the notion of going from electro to polyprop with ESR values to calculate seems like a compromise at best.
Would it make sense economic sense to buy new air coil inductors and polyprops to conform to the ideal crossover points? I want my speakers to sound as good as they can. These drivers are really superb. Maybe it's a bit geeky and obsessive all this, but well, that's me! I could get all the caps for about £50 I reckon What about inductors?
Thanks, Lucas
If I find out the crossover points for the 3 drivers from Celestion, would making or even buying new crossovers be a simple matter, or complex? I ask because the notion of going from electro to polyprop with ESR values to calculate seems like a compromise at best.
Would it make sense economic sense to buy new air coil inductors and polyprops to conform to the ideal crossover points? I want my speakers to sound as good as they can. These drivers are really superb. Maybe it's a bit geeky and obsessive all this, but well, that's me! I could get all the caps for about £50 I reckon What about inductors?
Thanks, Lucas
Sounds of the caps ?
Thanks for your reply tinitus !
What does the 100uF mystery dielectric cap sound like
in comparison to other caps you have used for mids' highpass ?
Those PIOs look good - you are fortunate -
- I hope none of them are electrically leaky !
You can use all the same uF value in parallel if you use all the same type of cap,
and as you have 2 types of PIOs you have choice of 2 types of multiples of 8uF.
My experience is that different internal widths of capacitors' plates cause the audible problem when 2 or more different internal width caps are used in parallel.
The plate width is the distance between the 2 connection terminals in most modern Axial and Radial plastic film caps, but it could be anything inside an old PIO !
Caps only have the sellers company name written
Relabelled, noone knows where they come from
Well, the only cap I have used is 100uf, on mids highpass
Dialectric is possible the cheapest
Ofcourse there are better caps
But I guess they are ok, and cheap
How good they are, I dont know
These NOS pios I got fore free
Unfortunately all 8uf
Thanks for your reply tinitus !
What does the 100uF mystery dielectric cap sound like
in comparison to other caps you have used for mids' highpass ?
Those PIOs look good - you are fortunate -
- I hope none of them are electrically leaky !
You can use all the same uF value in parallel if you use all the same type of cap,
and as you have 2 types of PIOs you have choice of 2 types of multiples of 8uF.
My experience is that different internal widths of capacitors' plates cause the audible problem when 2 or more different internal width caps are used in parallel.
The plate width is the distance between the 2 connection terminals in most modern Axial and Radial plastic film caps, but it could be anything inside an old PIO !
2 options
Hi Lucas,
see my replies after each of your points, after the ----> in the box below:-
Hi Lucas,
see my replies after each of your points, after the ----> in the box below:-
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Hi Alan,
Thanks once again for your advice. All excellent stuff! I will certainly look for some 66 x-overs! The 72uF bipolars you can link to sound ideal - I think the bass is already very nice indeed on these speakers, but the caps are old. If I have a problem with the sound, it is that they sound very good when played fairly loud, but lack detail at lower volumes, so I end up listening too loud, and can't sustain that. I guess it's partly a common issue with larger speakers, but also the caps surely could be responsible.
I wonder if I can get your advice on buying caps to replace:
I need 4x 6uF caps (to replace 3x2uF tweeter caps & 6uF midrange electros), 2x 4uF caps (to replace 2x2uF tweeter caps) and 2x 33uF caps (to replace 25uF+8uF midrange electros).
I will keep the 2x72uF bass caps as they are for the moment, and use the bipolars you have sourced soon enough.
I will use only polypropylene axial capacitors, as cheaply as I can get away with. I'm building them on separate boards, to avoid disaster - I have a spare pair of crossover boards, with coils in place, so I can't ruin my original crossovers if I get it all wrong...
The 4uFs are easy:
Supersound 4uF £8.20 for both - Wimslow audio on eBay!
The 6uFs are tougher. It's mostly 5.6 or 6.8. Supersound 5.6mF are £4.80 each and I need 4, so that's £20. Would that be a close enough value?
For the 33s, Tinitus recommended PCA in Denmark, who do them to the exact 33uF value and cheap, but I'm not sure what the dielectric is. Surely if it was indeed polypropylene, they'd say so...? More likely polyester? I also note that the later PCB based 44s had only a single 24uF cap, whereas my earlier point to point 44s have a 25uF paralleled with an 8uF. Would the coils be made to match that? I mean, should I stick to the original 33uF to avoid an overlap/missed frequency, go with the later 25uF, or is Supersound's 30uF a good compromise between the two versions, in your opinion?
Many thanks for your help once again. Sorry if I seem ignorant - I am trying to learn...
Lucas
Thanks once again for your advice. All excellent stuff! I will certainly look for some 66 x-overs! The 72uF bipolars you can link to sound ideal - I think the bass is already very nice indeed on these speakers, but the caps are old. If I have a problem with the sound, it is that they sound very good when played fairly loud, but lack detail at lower volumes, so I end up listening too loud, and can't sustain that. I guess it's partly a common issue with larger speakers, but also the caps surely could be responsible.
I wonder if I can get your advice on buying caps to replace:
I need 4x 6uF caps (to replace 3x2uF tweeter caps & 6uF midrange electros), 2x 4uF caps (to replace 2x2uF tweeter caps) and 2x 33uF caps (to replace 25uF+8uF midrange electros).
I will keep the 2x72uF bass caps as they are for the moment, and use the bipolars you have sourced soon enough.
I will use only polypropylene axial capacitors, as cheaply as I can get away with. I'm building them on separate boards, to avoid disaster - I have a spare pair of crossover boards, with coils in place, so I can't ruin my original crossovers if I get it all wrong...
The 4uFs are easy:
Supersound 4uF £8.20 for both - Wimslow audio on eBay!
The 6uFs are tougher. It's mostly 5.6 or 6.8. Supersound 5.6mF are £4.80 each and I need 4, so that's £20. Would that be a close enough value?
For the 33s, Tinitus recommended PCA in Denmark, who do them to the exact 33uF value and cheap, but I'm not sure what the dielectric is. Surely if it was indeed polypropylene, they'd say so...? More likely polyester? I also note that the later PCB based 44s had only a single 24uF cap, whereas my earlier point to point 44s have a 25uF paralleled with an 8uF. Would the coils be made to match that? I mean, should I stick to the original 33uF to avoid an overlap/missed frequency, go with the later 25uF, or is Supersound's 30uF a good compromise between the two versions, in your opinion?
Many thanks for your help once again. Sorry if I seem ignorant - I am trying to learn...
Lucas
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I wouldnt worry about that
Poly is poly
Its more about the mechanical build, and tuning
Man, you can get the best DCA caps, but just because they are good doesnt mean nothing else works
Polypropylene is a cheap product spinning money, big time, and it means nothing, its really the worst, which goes fore cabls and all
Why not polycarbonate ?
If theres different values on the two xo version you have, that could complicate things a bit
Have you listened to both, is there any audible difference
But 25uf or 33uf both seems a bit on the small side
But whether it can be bigger depends on size of paralel inductor, and other things
And we still have no clew about the size of ANY of the inductors
You do the listening, and only you can judge about any of it
You know, none of us have a magic stick to swing over your speakers
Maybe read the whole thread over again
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Both the crossovers in my speakers, and the spare boards I have are the same. However the later Mk2 speakers (which are thought by some to sound inferior) had a PCB crossover, with the same cap values except 24uF in place of the 25+8uF, probably because the magnet size was increased on the mid driver. I'll stick to my version.
Tinitus, what do you think about using a 30uF in place of 33uF for the midrange. Am I right in thinking that this cap cuts out the treble from the signal for the midrange, and that lowering the value will slightly raise that cut-off level?
Many thanks
Lucas
Tinitus, what do you think about using a 30uF in place of 33uF for the midrange. Am I right in thinking that this cap cuts out the treble from the signal for the midrange, and that lowering the value will slightly raise that cut-off level?
Many thanks
Lucas
As I recall its a series cap on midrange, hence its a highpass filter, lowering mids midbass level
The following paralel inductor makes the cap more effective, lowering impedance
Maybe you should experiment a bit before going fore the big buying
You will need only a few small and cheap components, at least fore your specific question
You can try to ad various small caps in paralel with the existing 25uf/8uf
If you want to see if 30 works, replace the 8uf with a 4.7uf(?)
If you do have a 4.7uf, or similar, also try to place in on the existing 25uf/8uf, making a 37uf
And so forth
You could do the same with resistors
If I want to hear if a smaller resistor would sound better, say a 6.8ohm, I place a much bigger resistor in paralel, making it a bit smaller
If it sounds better, it MAYBE need to be smaller
If it sounds worse, MAYBE resistor should be bigger
I adjust only one channel at a time and listen carefully
Usually it takes only a few seconds to decide
The tricky things is that even if one channel sounds better, it might happen that it doesnt work at all when both channels are made that way
Thats how I work
It can be very tedious, but it works
Inductors are a bit more tricky
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Polypropylene is NOT similar to Polyester, nor to Polycarbonate !
Sorry tinitus,
but all the Polys are different in molecular structure, and in their behavior when subject to electrical current through them, and it is too complicated for me to have time to explain all that here.
There are explanations available in Text Books about the Chemistry of Plastics.
See my Post #48 on Page 5
where I describe the internal electrical behavior of a capacitor.
"Mylar" is basically a Polyester type -{it is a Trademark name, though now-a-days Polyester types are refered to in general as Mylar}.
Polyester caps exhibit all those additional effects, albeit less so than Electrolytics.
Polycarbonate caps exhibit those effects in lesser degree than Polyester,
but to greater degree than Polypropylene and Polystyrene and Teflon,
{none of which are equal chemically, but are of somewhat similar behavior in capacitors}.
The differences are audible.
Where I do agree with you is about the "mechanical build".
When a capacitor is able to vibrate internally when subject to voltage induced stress
it behaves like a microphone - the piezoelectric effect - and this causes audible colouration of the sound in the frequency bands where the internal resonance is occurring.
The better sounding caps are more tightly wound, and better mechanically damped,
but this cannot be easily recognised from inspecting the outside,
thus one has to listen, or buy a Brand Name that has been made well mechanically.
****************************************************
I Posted what I know so far about the Inductors in #51 above.
Sorry tinitus,
but all the Polys are different in molecular structure, and in their behavior when subject to electrical current through them, and it is too complicated for me to have time to explain all that here.
There are explanations available in Text Books about the Chemistry of Plastics.
See my Post #48 on Page 5
where I describe the internal electrical behavior of a capacitor.
"Mylar" is basically a Polyester type -{it is a Trademark name, though now-a-days Polyester types are refered to in general as Mylar}.
Polyester caps exhibit all those additional effects, albeit less so than Electrolytics.
Polycarbonate caps exhibit those effects in lesser degree than Polyester,
but to greater degree than Polypropylene and Polystyrene and Teflon,
{none of which are equal chemically, but are of somewhat similar behavior in capacitors}.
The differences are audible.
Where I do agree with you is about the "mechanical build".
When a capacitor is able to vibrate internally when subject to voltage induced stress
it behaves like a microphone - the piezoelectric effect - and this causes audible colouration of the sound in the frequency bands where the internal resonance is occurring.
The better sounding caps are more tightly wound, and better mechanically damped,
but this cannot be easily recognised from inspecting the outside,
thus one has to listen, or buy a Brand Name that has been made well mechanically.
****************************************************
I Posted what I know so far about the Inductors in #51 above.
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I know that, I just dont care much about it
To me this concern about dialectrics is mostly about mass hysteria
It means nothing on its own
Other things matter more
The best poly is NO poly
They all have one thing in common, they are all plastics
Sure, if you need something stable at 500khz, it would matter
But basicly, the better dialectric, the worse it sounds
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Use what you like the sounds from
Then you may as well use the worst dialectrics - such as in the oldest electrolytic caps - if they sound less worse to you than "better dielectric".
Why do you bother with PIOs if their better dielectric sounds worse than Electrolytics ?
Ultimately one can use what one prefers the sound from,
but I advise that new listeners hear caps with better dielectrics than the caps they have heard to date, and then they can decide.
I suspect that some of these "better dielectric" caps you do not like the sounds from are poorly assembled and exhibit the piezoelectric effect
I described in #57 above.
Is your 100uF Danish branded PCA better or worse sounding to you than what you had in the mids' filter before it ?
and, what cap type did you have in there before the PCA ?
*****************************************************************************
Warning to All :-
be wary of any cheap price caps that do not have any, or sufficient,
Type and Series identification markings on them.
If you are on low budget, you may be wasting your money.
If you have plenty of money, then buy those and do comparative listening of those versus other caps.
One does not have to buy only the most expensive caps - and I don't -
but research what quality Loudspeaker Manufacturers are using in their best models,
and what the long-time experienced DIYers are using.
There is plenty of discussion about capacitors in Threads in this Forum.
Then you may as well use the worst dialectrics - such as in the oldest electrolytic caps - if they sound less worse to you than "better dielectric".
Why do you bother with PIOs if their better dielectric sounds worse than Electrolytics ?
Ultimately one can use what one prefers the sound from,
but I advise that new listeners hear caps with better dielectrics than the caps they have heard to date, and then they can decide.
I suspect that some of these "better dielectric" caps you do not like the sounds from are poorly assembled and exhibit the piezoelectric effect
I described in #57 above.
Is your 100uF Danish branded PCA better or worse sounding to you than what you had in the mids' filter before it ?
and, what cap type did you have in there before the PCA ?
*****************************************************************************
Warning to All :-
be wary of any cheap price caps that do not have any, or sufficient,
Type and Series identification markings on them.
If you are on low budget, you may be wasting your money.
If you have plenty of money, then buy those and do comparative listening of those versus other caps.
One does not have to buy only the most expensive caps - and I don't -
but research what quality Loudspeaker Manufacturers are using in their best models,
and what the long-time experienced DIYers are using.
There is plenty of discussion about capacitors in Threads in this Forum.
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I said it was cheap, costwise
I also said I have only tried it as series cap on midrange, 150uf, where its ok
PIO(paper in oil) doesnt have very good dialectrics, does it
Good dialectrics is measured in the 100khz range an up, isnt it
PIOs fail before the plastics, but still above 100khz
The best of all, DCA, are PIOs, right
But this I suppose is not really about finding the best possible, but the cheapest possible
I also said that how your speaker sounds is not about dialectrics, but solely a matter of design
edit
Forgot to mention that in a 3way I rate the mid series cap as maybe the most critical cap, not the tweeter cap
The PCA seem to work fine in that position
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