Audio Frequencies versus Radio Frequencies
"Good Dielectric" ?
What is the optimum dielectric is largely determined by the particular application:-
(1) - the frequency band.
(2) - how stable it has to be under conditions of heat and cold - such as in Aerospace and Military applications, etc ...
(3), etc ... other matters not relevant to Passive Cross-overs.
What is optimum for a specific Radio Frequencies' band use is not necessarily what is optimum for the Audio Frequencies' band,
and, what is sometimes necessary for use inside Audio Electronics' equipment is not necessarily what is optimum for use in Passive cross-overs.
100kHz and above is R.F.
There is no 100kHz application in a Passive cross-over,
nor excess hot/cold if suitable voltage rated caps are used and the cross-over is not put in direct mid-day Summer sun or Winter snow.
For use in a Passive cross-over for lowest audible colouration what one needs is the lowest Dielectric Absorption -{D.A.}- possible
plus the lowest electrical leakage so that the cross-over will work well.
For practical and affordable circumstances that means using Polypropylene as dielectric.
If one doesn't mind risking electrical leakage, then some listeners prefer the sound of PIOs, but new PIOs are expensive,
thus not relevant here for Lucas and Lorien.
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Dielectric types, and Series and Parallel circuits
I agree with you about the priority of the mid-range cap in a 3-way design,
but not only the Series cap, but also any Parallel connected cap,
because Audio signal oscillates.
Anything oscillating across a Parallel connected device is coupled into that device, and here it is in quantities in proportion to the relative Impedances of the cap and the speaker, and across the entire frequency band of the coupling.
Some Manufacturers give as excuse for using an electro cap in Parallel that it matters less.
Some Kit designers specify electrolytics for Parallel application to keep the costs down.
The only compromise I will make for Parallel connected caps is in woofer application, because the resonant colourations in the woofer circuit are often of similar magnitude and duration to those in an electrolytic cap,
{but do not misunderstand and think that one source of colouration here can cancel out the other - they don't -
and it is very complicated and time-consuming to explain why - and better is to try the caps and listen}.
The only Danish "PCA Frequence" cap I think is worth budget contrained DIYers trying in Celestion's 44 and 66 is the 75uF/100volt,
which at 102,95 DKK is about 12.55 GBP at the current exchange rate, but a 72uF Alcap is only 1.72 GBP, thus decide on the basis of your budget,
and whether the PCA cap, being 6" long, will fit on your board ..(?)
The PCA cap will likely last forever, and the Alcap will last about 5 <---> 10 years -
- the more frequently used the longer electrolytics work, but when not often used they start to fail.
{Old electros that have been long in storage may not work at all.}
"Good Dielectric" ?
What is the optimum dielectric is largely determined by the particular application:-
(1) - the frequency band.
(2) - how stable it has to be under conditions of heat and cold - such as in Aerospace and Military applications, etc ...
(3), etc ... other matters not relevant to Passive Cross-overs.
What is optimum for a specific Radio Frequencies' band use is not necessarily what is optimum for the Audio Frequencies' band,
and, what is sometimes necessary for use inside Audio Electronics' equipment is not necessarily what is optimum for use in Passive cross-overs.
100kHz and above is R.F.
There is no 100kHz application in a Passive cross-over,
nor excess hot/cold if suitable voltage rated caps are used and the cross-over is not put in direct mid-day Summer sun or Winter snow.
For use in a Passive cross-over for lowest audible colouration what one needs is the lowest Dielectric Absorption -{D.A.}- possible
plus the lowest electrical leakage so that the cross-over will work well.
For practical and affordable circumstances that means using Polypropylene as dielectric.
If one doesn't mind risking electrical leakage, then some listeners prefer the sound of PIOs, but new PIOs are expensive,
thus not relevant here for Lucas and Lorien.
*********************************
Dielectric types, and Series and Parallel circuits
I agree with you about the priority of the mid-range cap in a 3-way design,
but not only the Series cap, but also any Parallel connected cap,
because Audio signal oscillates.
Anything oscillating across a Parallel connected device is coupled into that device, and here it is in quantities in proportion to the relative Impedances of the cap and the speaker, and across the entire frequency band of the coupling.
Some Manufacturers give as excuse for using an electro cap in Parallel that it matters less.
Some Kit designers specify electrolytics for Parallel application to keep the costs down.
The only compromise I will make for Parallel connected caps is in woofer application, because the resonant colourations in the woofer circuit are often of similar magnitude and duration to those in an electrolytic cap,
{but do not misunderstand and think that one source of colouration here can cancel out the other - they don't -
and it is very complicated and time-consuming to explain why - and better is to try the caps and listen}.
The only Danish "PCA Frequence" cap I think is worth budget contrained DIYers trying in Celestion's 44 and 66 is the 75uF/100volt,
which at 102,95 DKK is about 12.55 GBP at the current exchange rate, but a 72uF Alcap is only 1.72 GBP, thus decide on the basis of your budget,
and whether the PCA cap, being 6" long, will fit on your board ..(?)
The PCA cap will likely last forever, and the Alcap will last about 5 <---> 10 years -
- the more frequently used the longer electrolytics work, but when not often used they start to fail.
{Old electros that have been long in storage may not work at all.}
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Mk1 and Mk2 44 differences
Hah, good one Lucas - excellent that you Posted about the Magnet sizes !
The larger magnet will cause greater damping of the fundamental Resonant Frequency of the mid-cone in its enclosure -{its "Fo"}- and as that is at the low frequency end of its useable-in-enclosure band there will be a lower magnitude Impedance spike there than is with the smaller magnet version.
Voltage division is proportional to the magnitudes of the relative Series connected Impedances.
The Parallel connected components in the filter do reduce the effect of the larger Fo Impedance spike of the small magnet driver to some degree,
but not completely.
Using a larger Series cap means that there is a lower Impedance across the cap at the same frequency as the small magnet driver's Fo -
and the RATIO between those two Impedances will likely be similar to the RATIO of Impedances between those of the 24uF cap and the larger magnet driver's at that driver's Fo.
The low frequency roll-off of the two drivers will likely be a bit different also, and that combines with the electrical filter's roll-off,
thus I recommend using the same cap size as Celestion used for each version - 33uF for Mk1 and 24uF for Mk2
-{unless one has equipment to make measurements to determine what may work better for their particular samples}.
Using 30uF will roll-off a bit more of the lower midrange than 33uF will.
If you want to play your speakers very loudly, then reducing the lower end of the bandwidth fed to the mid-cone will allow it to dissipate more of its power in the remainder of its range.
If you want to do this you could try to fill in the thus caused low midrange gap by reducing the 72uF cap that is electrically closest to the woofer to 68uF,
AND/OR, by lifting that closest cap electrically above its Ground return with a Series connected resistor of somewhere between 1 ohm <---> 2.2 ohm, if staying with electro caps, or with 1.5 ohm <---> 3.9 ohm if changing to poly caps there -{1.5 ohm + 68uF, or 3.9 ohm + 75uF}.
I do not know the exact audio result - I would have to try in Mk1 44s and listen, thus decide your volume level requirements first.
A wirewound resistor of at least 5 watts rating would be necessary.
Hah, good one Lucas - excellent that you Posted about the Magnet sizes !
The larger magnet will cause greater damping of the fundamental Resonant Frequency of the mid-cone in its enclosure -{its "Fo"}- and as that is at the low frequency end of its useable-in-enclosure band there will be a lower magnitude Impedance spike there than is with the smaller magnet version.
Voltage division is proportional to the magnitudes of the relative Series connected Impedances.
The Parallel connected components in the filter do reduce the effect of the larger Fo Impedance spike of the small magnet driver to some degree,
but not completely.
Using a larger Series cap means that there is a lower Impedance across the cap at the same frequency as the small magnet driver's Fo -
and the RATIO between those two Impedances will likely be similar to the RATIO of Impedances between those of the 24uF cap and the larger magnet driver's at that driver's Fo.
The low frequency roll-off of the two drivers will likely be a bit different also, and that combines with the electrical filter's roll-off,
thus I recommend using the same cap size as Celestion used for each version - 33uF for Mk1 and 24uF for Mk2
-{unless one has equipment to make measurements to determine what may work better for their particular samples}.
Using 30uF will roll-off a bit more of the lower midrange than 33uF will.
If you want to play your speakers very loudly, then reducing the lower end of the bandwidth fed to the mid-cone will allow it to dissipate more of its power in the remainder of its range.
If you want to do this you could try to fill in the thus caused low midrange gap by reducing the 72uF cap that is electrically closest to the woofer to 68uF,
AND/OR, by lifting that closest cap electrically above its Ground return with a Series connected resistor of somewhere between 1 ohm <---> 2.2 ohm, if staying with electro caps, or with 1.5 ohm <---> 3.9 ohm if changing to poly caps there -{1.5 ohm + 68uF, or 3.9 ohm + 75uF}.
I do not know the exact audio result - I would have to try in Mk1 44s and listen, thus decide your volume level requirements first.
A wirewound resistor of at least 5 watts rating would be necessary.
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DC Resistance of the Inductors, and capacitor prices.
Measure the DC Resistance of the three cored inductors in your cross-overs, and Post those here.
Air core inductors have larger DC resistances for small size coils, and that will cause changes to the bass sound.
Larger wire diameter air-core inductors have lower DC resistances,
but these cost quite a LOT more, and they are larger size thus require more space to fit.
Two, perhaps three, may fit OK on your boards, and not too close to each other.
Slightly higher DCR will not be a problem for the inductor in the parallel position in the mids' filter,
but you may not like the sound of higher DCR inductors in Series with the bass driver,
and especially because there are two of them there adding the effects of Series resistance.
And again you will have to consider budget also.
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I will Post some prices for suitable 4uF; 6uF ; 33uF caps next time - I have to go now.
Will you only buy from a UK seller, or can you buy from a Continental EU seller ?
Measure the DC Resistance of the three cored inductors in your cross-overs, and Post those here.
Air core inductors have larger DC resistances for small size coils, and that will cause changes to the bass sound.
Larger wire diameter air-core inductors have lower DC resistances,
but these cost quite a LOT more, and they are larger size thus require more space to fit.
Two, perhaps three, may fit OK on your boards, and not too close to each other.
Slightly higher DCR will not be a problem for the inductor in the parallel position in the mids' filter,
but you may not like the sound of higher DCR inductors in Series with the bass driver,
and especially because there are two of them there adding the effects of Series resistance.
And again you will have to consider budget also.
************************************
I will Post some prices for suitable 4uF; 6uF ; 33uF caps next time - I have to go now.
Will you only buy from a UK seller, or can you buy from a Continental EU seller ?
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Alan, your commitment and strong belief is very impressive
Sorry, but the above statement is just another claim that makes me wonder and doubt even more
But at least you are trying to help the man, and that alone counts fore something
Hmmm....Well, I certainly appreciate your help Alan. Anyway, I have taken the plunge and bought replacement polyprops - 4uF & 5.6uF for the tweeter series caps (Supersound caps from Wilmslow Audio) 5.6uF for the midrange earthing cap, (again Wilmslow) and for the very important midrange series cap I plunged for 33uF 250v Soniqs PXX, mostly because they were exact, available and cheap(ish).
The voltages are way higher than the originals, which I hope is OK. 5.6es replace the 6es, which is close enough I guess. Have you used any of these brands? Heard anything good or bad about them?
I'll keep you posted. Any discrepancy in the crossover points or slopes will have to be lived with. I predict that the benefits will outweigh the issues.
I will post the inductance values of the iron cores when I get a meter - it's on order! If you can post a source of 72uF electros, I'd be stoked! I plan on making 6 new inductors at some point in the near future.
Many thanks
Lucas
The voltages are way higher than the originals, which I hope is OK. 5.6es replace the 6es, which is close enough I guess. Have you used any of these brands? Heard anything good or bad about them?
I'll keep you posted. Any discrepancy in the crossover points or slopes will have to be lived with. I predict that the benefits will outweigh the issues.
I will post the inductance values of the iron cores when I get a meter - it's on order! If you can post a source of 72uF electros, I'd be stoked! I plan on making 6 new inductors at some point in the near future.
Many thanks
Lucas
Correcting my mistake in #62
I should have re-read this twice and thought about it before Posting it !
The RATIO of the two Impedances will NOT be similar for the lower Fo damping magnet + 32uF versus the higher Fo damping magnet + 24uF.
It will be quite different.
What I should have written is:-
The smaller magnet's lesser damping of the Fo will result in a steeper initial slope of the low-end roll-off of the driver than the larger magnet's greater damping of the Fo.
The latter's greater damping will cause an initially less steep slope, thus a smaller capacitor with its higher Reactance at the Fo is needed to steepen the roll-off slope so that the roll-off rate and the Phase Shift at 500Hz is similar for the Mk2 44 to what it is for the Mk1 44 because both use the same bass filter at 500Hz.
32uF has lower Reactance at 500Hz than 24uF, thus less Phase Shift caused by it there, but when added to the greater Phase Shift of the steeper roll-off older driver the Total will be similar to that of the later driver's + 24uF's Phase Shift at 500Hz.
A bit Wordy eh !
I suspect there may be a slightly different Fo for each mid-cone version also.
The older 44 will distort in the lower midrange at a lower power level than the Mk2 44 whose larger magnet should control the voice-coil and thereby the cone to greater degree around the cross-over region, unless there have been other relevant changes to the later driver also.
I should have re-read this twice and thought about it before Posting it !
The RATIO of the two Impedances will NOT be similar for the lower Fo damping magnet + 32uF versus the higher Fo damping magnet + 24uF.
It will be quite different.
What I should have written is:-
The smaller magnet's lesser damping of the Fo will result in a steeper initial slope of the low-end roll-off of the driver than the larger magnet's greater damping of the Fo.
The latter's greater damping will cause an initially less steep slope, thus a smaller capacitor with its higher Reactance at the Fo is needed to steepen the roll-off slope so that the roll-off rate and the Phase Shift at 500Hz is similar for the Mk2 44 to what it is for the Mk1 44 because both use the same bass filter at 500Hz.
32uF has lower Reactance at 500Hz than 24uF, thus less Phase Shift caused by it there, but when added to the greater Phase Shift of the steeper roll-off older driver the Total will be similar to that of the later driver's + 24uF's Phase Shift at 500Hz.
A bit Wordy eh !
I suspect there may be a slightly different Fo for each mid-cone version also.
The older 44 will distort in the lower midrange at a lower power level than the Mk2 44 whose larger magnet should control the voice-coil and thereby the cone to greater degree around the cross-over region, unless there have been other relevant changes to the later driver also.
about Post #64
Hello tinitus,
as you "wonder and doubt" , I recommend you take a 30uF and a 33uF , or any two caps that differ in value by 10%,
and connect each in turn to a convenient resistance and send a sine wave of a suitable frequency through that C + R network and measure the AC voltages across the resistor and across the cap.
Next, with the signal frequency and output level unchanged, substitute the other cap and measure both voltages again.
You will see the difference, and if you can sweep the signal frequency to where there is equal voltages across the resistance and one of the caps,
then when the other cap is substituted the voltage across it and the resistor will not be equal.
Similarly, the voltages will not be equal at that frequency when different value caps and a driver are connected in Series,
nor even when the same inductor is connected to Ground between the cap and the driver.
Hello tinitus,
as you "wonder and doubt" , I recommend you take a 30uF and a 33uF , or any two caps that differ in value by 10%,
and connect each in turn to a convenient resistance and send a sine wave of a suitable frequency through that C + R network and measure the AC voltages across the resistor and across the cap.
Next, with the signal frequency and output level unchanged, substitute the other cap and measure both voltages again.
You will see the difference, and if you can sweep the signal frequency to where there is equal voltages across the resistance and one of the caps,
then when the other cap is substituted the voltage across it and the resistor will not be equal.
Similarly, the voltages will not be equal at that frequency when different value caps and a driver are connected in Series,
nor even when the same inductor is connected to Ground between the cap and the driver.
Inductors in Celestion 66
The inductors in the bass filter of the 66 are a bit higher in resistance than suitable for well controlled bass from that low impedance driver,
however some listeners like an underdamped bass sound, AND in the case of the 66 the bass driver has to control the ABR also.
The combination of the back-pressure changes of air pressure caused in the enclosure by the ABR moving, plus the underdamped bass driver, together cause a unique bass sound for the 66,
and that is quite different to the bass sound from the 44 which has no moving ABR to affect its bass response.
I mentioned buying a 66 cross-over to get the inductors cheaply - if you can find two crossovers at low price, and they are only worth a low price because the caps are no good, but some sellers will price them at same price as cost of 5 new inductors plus wired board.
I wouldn't pay more than 20 quid each, and preferably less, and I think 15 would be their true value -{other than Vintage Collectors' value}- and 10 quid each a bargain !
Three new air-core inductors will cost you about 15 in the UK, -{30 for the pair for 2 crossovers}-, for ones of similar DC resistance,
-{and quite a bit higher price for lower DCR, and those will be a lot physically larger}.
It is possible the Jantzen P-core -{Permite}- inductors with their low DCR and small size may be suitable, as it is claimed those do not saturate as soon as ferrite cored inductors.
I am interested in them myself, so I will investigate those a bit further ...
Try with your new caps first, then consider inductors later, unless you can find cheap 66 crossovers now.
The inductors in the bass filter of the 66 are a bit higher in resistance than suitable for well controlled bass from that low impedance driver,
however some listeners like an underdamped bass sound, AND in the case of the 66 the bass driver has to control the ABR also.
The combination of the back-pressure changes of air pressure caused in the enclosure by the ABR moving, plus the underdamped bass driver, together cause a unique bass sound for the 66,
and that is quite different to the bass sound from the 44 which has no moving ABR to affect its bass response.
I mentioned buying a 66 cross-over to get the inductors cheaply - if you can find two crossovers at low price, and they are only worth a low price because the caps are no good, but some sellers will price them at same price as cost of 5 new inductors plus wired board.
I wouldn't pay more than 20 quid each, and preferably less, and I think 15 would be their true value -{other than Vintage Collectors' value}- and 10 quid each a bargain !
Three new air-core inductors will cost you about 15 in the UK, -{30 for the pair for 2 crossovers}-, for ones of similar DC resistance,
-{and quite a bit higher price for lower DCR, and those will be a lot physically larger}.
It is possible the Jantzen P-core -{Permite}- inductors with their low DCR and small size may be suitable, as it is claimed those do not saturate as soon as ferrite cored inductors.
I am interested in them myself, so I will investigate those a bit further ...
Try with your new caps first, then consider inductors later, unless you can find cheap 66 crossovers now.
Thanks again Alan.
I will fit the caps before considering buying or making coils
The costs you quote for new coils are pretty low. I will probably make my own low DCR coils. Do you know where I can buy the plastic bobbins? I can't find them anywhere.
Also, I have two 44 boards, hence two sets of inductors. I am totally unsure of the values, but presumably the air-cores are are the same as those in the 66 for the identical tweeter parallel coil, and similar for the midrange series coil. Could either of the spares be used, or else shortened to fit in elsewhere? If so, I'll do it at the same time as the cap swap.
Many thanks
Lucas
I will fit the caps before considering buying or making coils
The costs you quote for new coils are pretty low. I will probably make my own low DCR coils. Do you know where I can buy the plastic bobbins? I can't find them anywhere.
Also, I have two 44 boards, hence two sets of inductors. I am totally unsure of the values, but presumably the air-cores are are the same as those in the 66 for the identical tweeter parallel coil, and similar for the midrange series coil. Could either of the spares be used, or else shortened to fit in elsewhere? If so, I'll do it at the same time as the cap swap.
Many thanks
Lucas
Suitable lower price capacitors, and Resistors.
Hello Lucas - look in your "Private Messages" file on this web-site.
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For 72uF/100 volt bipolar electrolytic caps, go to:-
AudioLoudspeakers <--- Click on this.
and to their "Components" page, then to "Capacitors", then look under "Alcap" 100v.
Scroll down to 72uF @1.62,
then scroll down to the bottom of that page to see exactly how that cap has to be ordered.
This company has 4uF and 6uF in 400volt "Solen" metalized polypropylene at low prices,
but a little better can be bought from:-
Save money by building your own high performance loudspeakers or those who want to install their own home cinema, surround-sound or multi-room home entertainment system <--- Click on this.
go to their "Crossover Components" page, then to "Capacitors", then to "Cross Caps" -{the black ones}.
These are 400volt rated, and use a Zinc-Aluminium alloy for their metalization, and that may be better than the plain Aluminium of most other MKP types.
On the first page of is 33uF @7.52 including UK Postage !
On the second page is 6.2uF @3.26 including UK Postage,
and 3.9uF @2.13 including UK Postage.
Tolerance is +/- 5%.
3.9uF is so close to 4uF that the difference will not be heard,
and similarly for 6.2uF versus 6uF,
and those as slightly lower and slightly higher values in Series in the 44 cross-over will part compensate for each other,
AND they are in the correct proportions for their relative capacitance values in a 3rd Order cross-over, which this one is.
I would buy these instead of "Solen".
Wilmslow Audio "Supersound" are 400 volt "Solen" re-branded.
For those who can buy from USA, all the above cap values are available from Madisound in ClarityCap PX series at good prices, and from Sonic Craft in "Sonicap", both of which are said by various DIY users to be better sounding audio caps.
I like the ClarityCaps, and soon I will be trying the Sonicaps.
UK "Soniqs" branded are ClarityCaps, but unfortunately only available in a limited range of values.
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Resistors will have to be installed in electrical Series with the 33uF and 6uF caps in the midrange filter to simulate the ESR of the original electrolytic caps there OR otherwise the crossover points will change AND the slopes of the filters will change.
Add 2.7ohm/5watt wirewound in Series between the 6uF and Ground.
Add at least 1ohm, preferably 1.5ohm, and a bit larger if you don't want a too-forward mids' sound, in 5watt wirewound in Series with the 33uF cap.
Time has run out.
I have to go now.
I continue this next time.
Hello Lucas - look in your "Private Messages" file on this web-site.
*************************************************
For 72uF/100 volt bipolar electrolytic caps, go to:-
AudioLoudspeakers <--- Click on this.
and to their "Components" page, then to "Capacitors", then look under "Alcap" 100v.
Scroll down to 72uF @1.62,
then scroll down to the bottom of that page to see exactly how that cap has to be ordered.
This company has 4uF and 6uF in 400volt "Solen" metalized polypropylene at low prices,
but a little better can be bought from:-
Save money by building your own high performance loudspeakers or those who want to install their own home cinema, surround-sound or multi-room home entertainment system <--- Click on this.
go to their "Crossover Components" page, then to "Capacitors", then to "Cross Caps" -{the black ones}.
These are 400volt rated, and use a Zinc-Aluminium alloy for their metalization, and that may be better than the plain Aluminium of most other MKP types.
On the first page of is 33uF @7.52 including UK Postage !
On the second page is 6.2uF @3.26 including UK Postage,
and 3.9uF @2.13 including UK Postage.
Tolerance is +/- 5%.
3.9uF is so close to 4uF that the difference will not be heard,
and similarly for 6.2uF versus 6uF,
and those as slightly lower and slightly higher values in Series in the 44 cross-over will part compensate for each other,
AND they are in the correct proportions for their relative capacitance values in a 3rd Order cross-over, which this one is.
I would buy these instead of "Solen".
Wilmslow Audio "Supersound" are 400 volt "Solen" re-branded.
For those who can buy from USA, all the above cap values are available from Madisound in ClarityCap PX series at good prices, and from Sonic Craft in "Sonicap", both of which are said by various DIY users to be better sounding audio caps.
I like the ClarityCaps, and soon I will be trying the Sonicaps.
UK "Soniqs" branded are ClarityCaps, but unfortunately only available in a limited range of values.
*******************************************************
Resistors will have to be installed in electrical Series with the 33uF and 6uF caps in the midrange filter to simulate the ESR of the original electrolytic caps there OR otherwise the crossover points will change AND the slopes of the filters will change.
Add 2.7ohm/5watt wirewound in Series between the 6uF and Ground.
Add at least 1ohm, preferably 1.5ohm, and a bit larger if you don't want a too-forward mids' sound, in 5watt wirewound in Series with the 33uF cap.
Time has run out.
I have to go now.
I continue this next time.
Resistors continued ... plus about metal in capacitors
(1) - After what-ever was the original development of film capacitors,
Tin was next used for the metal inside, and that is said to be better than Aluminium.
It seems that Aluminium has been used instead of Tin because it is cheaper and/or easier to use.
I have forgotten the reasons that aluminium is not optimum for use in plastic film caps, but perhaps it may be that aluminium metalized plastic is harder to damp securely and thus resonates under applied voltage stress which causes additional internal voltage generation via the piezo-electric effect.
I do not know for sure, however I suspect a Zinc-Aluminium alloy may be less resonant in combination with the plastic film it is applied to as metalization.
Let's listen and decide !
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(2) - the ESR of an electrolytic cap is not constant - it varies across the frequency spectrum
-{but it is still a Resistance and Not a Capacitive Reactance}-
thus is different in the 500Hz region to what it is in the 5kHz region.
I estimated the ESR in the 5kHz region for the 6uF cap in the mids' filter, because that is primarily where it is acting,
however the 33uF cap is passing a wide band from below 500Hz to above 5kHz,
thus any fixed resistor added to simulate ESR will have to be a compromise.
If you prefer strong lower mids and non-prominent upper mids, then use a larger value resistor, perhaps as high as 2.7ohms, though I suggest starting a bit lower.
If you prefer prominent upper mids, and don't mind the lower mids being a bit recessed, then use 1ohm.
I'd start with 1.5 ohms, and listen, then decide what to do next.
The caps in the tweeter circuit do not need ESR simulating resistors, because the original caps were fairly low ESR,
BUT, the treble sound will be distinctly different with new polypropylene caps to what it was with the old caps,
and it MAY be a bit too much different in character to the sounds from the midrange driver.
To integrate the sounds from them both better I recommend adding about 0.5ohm in electrical Series between the 6uF cap and the tweeter.
This resistance is too low to noticeably attenuate the output level - it will only slightly modify the tone, to blend better with the character of the mids.
I'll Post about suitable types of 0.5ohm resistors next time.
I have to go now.
(1) - After what-ever was the original development of film capacitors,
Tin was next used for the metal inside, and that is said to be better than Aluminium.
It seems that Aluminium has been used instead of Tin because it is cheaper and/or easier to use.
I have forgotten the reasons that aluminium is not optimum for use in plastic film caps, but perhaps it may be that aluminium metalized plastic is harder to damp securely and thus resonates under applied voltage stress which causes additional internal voltage generation via the piezo-electric effect.
I do not know for sure, however I suspect a Zinc-Aluminium alloy may be less resonant in combination with the plastic film it is applied to as metalization.
Let's listen and decide !
******************
(2) - the ESR of an electrolytic cap is not constant - it varies across the frequency spectrum
-{but it is still a Resistance and Not a Capacitive Reactance}-
thus is different in the 500Hz region to what it is in the 5kHz region.
I estimated the ESR in the 5kHz region for the 6uF cap in the mids' filter, because that is primarily where it is acting,
however the 33uF cap is passing a wide band from below 500Hz to above 5kHz,
thus any fixed resistor added to simulate ESR will have to be a compromise.
If you prefer strong lower mids and non-prominent upper mids, then use a larger value resistor, perhaps as high as 2.7ohms, though I suggest starting a bit lower.
If you prefer prominent upper mids, and don't mind the lower mids being a bit recessed, then use 1ohm.
I'd start with 1.5 ohms, and listen, then decide what to do next.
The caps in the tweeter circuit do not need ESR simulating resistors, because the original caps were fairly low ESR,
BUT, the treble sound will be distinctly different with new polypropylene caps to what it was with the old caps,
and it MAY be a bit too much different in character to the sounds from the midrange driver.
To integrate the sounds from them both better I recommend adding about 0.5ohm in electrical Series between the 6uF cap and the tweeter.
This resistance is too low to noticeably attenuate the output level - it will only slightly modify the tone, to blend better with the character of the mids.
I'll Post about suitable types of 0.5ohm resistors next time.
I have to go now.
Resistors - types to buy
For the Tweeter series' connected resistor, ideally a non-inductive type should be used, because any Series connected Inductance will attenuate the upper treble level, even if only very slightly with the very small inductance present in a 0.5ohm, medium-low power, wirewound resistor.
Different Manufacturers list low-ohm resistors in different ways, thus you may see:-
0.47ohm; 0.51ohm; 470mohm; 500mohm; 510mohm; ... and even a 560mohm will be OK.
USA residents and Mail-Order buyers can obtain Mills MRA-5 , 5watt non-inductive wirewound in one of the above values.
Only 12watt Mills are available in the UK, and those are too large in size for this sensitive application in the treble, and no-where near that amount of power dissipation is required here.
The current at 5kHz and above is a fairly small part of music signals,
and thus through 0.5ohm there will only be a very small voltage drop, thus low power.
A good quality 2 watt resistor will suffice, but a metal element type is preferable because the connection of metal wire leads to metal resistive element is electrically more secure for small sensitive signals than what may be the case for mass-produced cheap resitors of other resistive element types, except for the special applications types made by "Vishay" and "Caddock".
In the UK a Caddock MP930 in 500mohm/2.25watt/non-inductive can be bought from "Farnell" for 3.55.
This is a small size Radial format resistor.
Solder carefully to its connection tabs, and those are the legs to support the resistor on.
Keep the body of the resistor in air - not touching anything - so that its entire surface area can remain at the same temperature.
Its 30watt rating is ONLY for when it is attached to a Heat Sink, and that is not practical, nor necessary, inside a loudspeaker enclosure.
It will remain quite cool inside during normal music playing in this application, even to quite high volume levels.
If you don't want to pay 3.55, then for low prices Farnell also sell:-
"Welwyn" good quality UK manufactured wirewounds.
Welwyn type WP2S is 2.5watt@25*C and is available in 470mohm and 560mohm for about 30p.
The Inductance will be very low for 500mohm in this 2.5watt size.
The WP*S series are an enhanced pulse handling capacity type, thus will be assembled very well, much better than for standard wirewounds, hence suitable for sensitive audio signals.
For the ESR simulating resistors in the midrange filter,
and in the bass filter for application if one has bought polypropylene caps to replace the electros there,
Welwyn WP4S is 4watts@25*C and will be sufficient power dissipation because only low ohm values are being used in those locations.
WP4S is available in 1ohm; 1.2; 1.5; 1.8; 2.2; 2.7; 3.3 and 3.9ohms.
If you can't buy from Farnell, then the basic Welwyn W** series wirewounds are available from various sellers.
Buy from their W22 series, and not from W21 series -{except for the 500mohm}- as those are a bit too low in power rating for these applications.
{For 500mohm a W21 is sufficient dissipation, but its not the ideal resistor to use in series with a tweeter,
but if you can't find better ... there are a lot worse !}.
One wants the resistors to stay cool inside the loudspeaker enclosure.
Hot resistors can work OK in Power Supply applications, but not in audio signal applications, especially if their temperature fluctuates with signal level because that causes voltage generation at the junctions between the wire leads and the resistive element.
For ALL resistors do not bend their leads at the junction with their bodies.
Leave at least 1/8" and preferably 1/4" of wire extending straight out, and bend it there.
Support the resistors body by standing it on its bent leads, and with the body not touching any surfaces - especially not touching the surfaces of capacitors or inductors.
***********************************************
I'll discuss winding one's own Inductors next time.
For the Tweeter series' connected resistor, ideally a non-inductive type should be used, because any Series connected Inductance will attenuate the upper treble level, even if only very slightly with the very small inductance present in a 0.5ohm, medium-low power, wirewound resistor.
Different Manufacturers list low-ohm resistors in different ways, thus you may see:-
0.47ohm; 0.51ohm; 470mohm; 500mohm; 510mohm; ... and even a 560mohm will be OK.
USA residents and Mail-Order buyers can obtain Mills MRA-5 , 5watt non-inductive wirewound in one of the above values.
Only 12watt Mills are available in the UK, and those are too large in size for this sensitive application in the treble, and no-where near that amount of power dissipation is required here.
The current at 5kHz and above is a fairly small part of music signals,
and thus through 0.5ohm there will only be a very small voltage drop, thus low power.
A good quality 2 watt resistor will suffice, but a metal element type is preferable because the connection of metal wire leads to metal resistive element is electrically more secure for small sensitive signals than what may be the case for mass-produced cheap resitors of other resistive element types, except for the special applications types made by "Vishay" and "Caddock".
In the UK a Caddock MP930 in 500mohm/2.25watt/non-inductive can be bought from "Farnell" for 3.55.
This is a small size Radial format resistor.
Solder carefully to its connection tabs, and those are the legs to support the resistor on.
Keep the body of the resistor in air - not touching anything - so that its entire surface area can remain at the same temperature.
Its 30watt rating is ONLY for when it is attached to a Heat Sink, and that is not practical, nor necessary, inside a loudspeaker enclosure.
It will remain quite cool inside during normal music playing in this application, even to quite high volume levels.
If you don't want to pay 3.55, then for low prices Farnell also sell:-
"Welwyn" good quality UK manufactured wirewounds.
Welwyn type WP2S is 2.5watt@25*C and is available in 470mohm and 560mohm for about 30p.
The Inductance will be very low for 500mohm in this 2.5watt size.
The WP*S series are an enhanced pulse handling capacity type, thus will be assembled very well, much better than for standard wirewounds, hence suitable for sensitive audio signals.
For the ESR simulating resistors in the midrange filter,
and in the bass filter for application if one has bought polypropylene caps to replace the electros there,
Welwyn WP4S is 4watts@25*C and will be sufficient power dissipation because only low ohm values are being used in those locations.
WP4S is available in 1ohm; 1.2; 1.5; 1.8; 2.2; 2.7; 3.3 and 3.9ohms.
If you can't buy from Farnell, then the basic Welwyn W** series wirewounds are available from various sellers.
Buy from their W22 series, and not from W21 series -{except for the 500mohm}- as those are a bit too low in power rating for these applications.
{For 500mohm a W21 is sufficient dissipation, but its not the ideal resistor to use in series with a tweeter,
but if you can't find better ... there are a lot worse !}.
One wants the resistors to stay cool inside the loudspeaker enclosure.
Hot resistors can work OK in Power Supply applications, but not in audio signal applications, especially if their temperature fluctuates with signal level because that causes voltage generation at the junctions between the wire leads and the resistive element.
For ALL resistors do not bend their leads at the junction with their bodies.
Leave at least 1/8" and preferably 1/4" of wire extending straight out, and bend it there.
Support the resistors body by standing it on its bent leads, and with the body not touching any surfaces - especially not touching the surfaces of capacitors or inductors.
***********************************************
I'll discuss winding one's own Inductors next time.
Last edited:
Hi Tinitus I'd suggest looking up Dielectric Absorbtion (DA) as a parameter of capactitors, if you don't think that different dialectrics can make a difference to the sound. Basically it is a measure of how much lag there is in a capacitor giving up it's energy. Ideally a capacitor should give back all of its stored energy instantly on demand.... however depending on the dialectric used it will range from almost instant to having quite a lag. It is the ones with the lag that cause the most problems... The issue is that they give up some of the energy when asked, and some of it a bit later... I think you should be able to see what the problem is with the energy that gets given up after it was required...
I've only read about the effects with respect to signals that are amplified, obviously any distortions introduced by a capacitor will be greatly increased if there is a gain stage following.... I don't know how much of an effect the DA will have when used in a crossover, but I guess the voltages and currents in a speaker can be quite high so my reasoning would tend to lead me to the conclusion that the effect should be audible.
It seems once again I'm posting this
A link to a section of Walt Jungs web site have a read of his picking capacitors articles. Yes they were written nearly 30 years ago (which is all the more reason for posting them as the myth that there is no difference in capacitor types seems to perpetuate) but they are well worth a read IMO
Tony.
I've only read about the effects with respect to signals that are amplified, obviously any distortions introduced by a capacitor will be greatly increased if there is a gain stage following.... I don't know how much of an effect the DA will have when used in a crossover, but I guess the voltages and currents in a speaker can be quite high so my reasoning would tend to lead me to the conclusion that the effect should be audible.
It seems once again I'm posting this
A link to a section of Walt Jungs web site have a read of his picking capacitors articles. Yes they were written nearly 30 years ago (which is all the more reason for posting them as the myth that there is no difference in capacitor types seems to perpetuate) but they are well worth a read IMO Tony.
Hi Tony
Sure it matters, everything matters
But like with everything else its mainly the construction that matters
If a component is poorly designed and manufactored no fancy material will save it
MKT caps are quite adequate
Those yellow ones sold from english company linked to ealier looks much like the flat/oval silver coulered ones sold through Monacor, and they are fine, but have become a bit costly
What I say is, even the worst dialectrical plastic thing still have better dialectrics than paper stuff
We also know that the best are wound with foil/paper
So, no I dont buy it
I also said I would avoid bipolar electrolyte caps at any cost
Or at least the cheap ones
I know there are better ones (smooth), but they also cost serious money, and available only in smaller values
The bigger ones are the roughed ones, and suppposed to be less good fore xo work
I admit I have only heard a few
But what I do know is that I can do a very high end design with the cheap ones
If any design depend on any exotic meterial, Im off
Im also fed up with all this non inductive stuff going on fore years now
The few film resistors I have tried all sounded significantly worse than the good old wirewound cement, no matter where its used
In my youth the most exotic caps were polycarbonate
Then out of the sky came polypropylene
People went mad and couldnt get enough
To me its just seemed to sound worse and worse the more of this nasty stuff being used
So no, any salesman would have a real hard time to convince me of anything
And the more they talk the worse it gets
Its all bogus to me
I keep my money in my pocket and spend them on more important things
Sure it matters, everything matters
But like with everything else its mainly the construction that matters
If a component is poorly designed and manufactored no fancy material will save it
MKT caps are quite adequate
Those yellow ones sold from english company linked to ealier looks much like the flat/oval silver coulered ones sold through Monacor, and they are fine, but have become a bit costly
What I say is, even the worst dialectrical plastic thing still have better dialectrics than paper stuff
We also know that the best are wound with foil/paper
So, no I dont buy it
I also said I would avoid bipolar electrolyte caps at any cost
Or at least the cheap ones
I know there are better ones (smooth), but they also cost serious money, and available only in smaller values
The bigger ones are the roughed ones, and suppposed to be less good fore xo work
I admit I have only heard a few
But what I do know is that I can do a very high end design with the cheap ones
If any design depend on any exotic meterial, Im off
Im also fed up with all this non inductive stuff going on fore years now
The few film resistors I have tried all sounded significantly worse than the good old wirewound cement, no matter where its used
In my youth the most exotic caps were polycarbonate
Then out of the sky came polypropylene
People went mad and couldnt get enough
To me its just seemed to sound worse and worse the more of this nasty stuff being used
So no, any salesman would have a real hard time to convince me of anything
And the more they talk the worse it gets
Its all bogus to me
I keep my money in my pocket and spend them on more important things
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Thanks Palerider - good advise, but as I'm being a cheapskate and using bipolar electros in the bass (ie replacing them) the ESR should be about the same, so no resistors required.
So you don`t use any impedancecorrection?
Oh, I forgot to say I know, or think I know, why those "crappy" oval/flat MKT sounds so good
Because they are "flat" pressured
When they pressure them after "rolling" they get a really tight construction
Mr Duelund also discouvered this through his many visits to the danish part of Jensen
It was the first step to the now famous DCA
His request fore a different and better leads connection was more difficult to fullfil
But he made it happen, in a small messy apartment in the middle of Copenhagen
He wholehartedly hated all this new fancy plastic stuff
He is truly missed
Because they are "flat" pressured
When they pressure them after "rolling" they get a really tight construction
Mr Duelund also discouvered this through his many visits to the danish part of Jensen
It was the first step to the now famous DCA
His request fore a different and better leads connection was more difficult to fullfil
But he made it happen, in a small messy apartment in the middle of Copenhagen
He wholehartedly hated all this new fancy plastic stuff
He is truly missed
Last edited:
The original design didn't use any, and in the bass circuit there are no changes being made. I am just replacing the 35 year old bipolar electrolytic 72uF caps with near identical modern bipolar electrolytic 72uF caps, so I don't think it's required, is it?
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