What Capacitor Is Better ?

[ka7niq]

I recently ordered some ERSE Poly Caps to re fresh my Cornwall 2's.

The ERSE Poly Caps are availiable in 250, 400, and 630VDC.

Initially, I ordered 250 volt caps.'

But, when I looked at the Red vs Blue Clarity Caps, I noticed Clarity Caps made a big deal that the more expensive Red Clarity Caps had a higher voltage rating,

So, I ordered the 400 and 600 volt version of the ERSE Poly Caps.

Then, I saw on Google that a thicker film cap with a higher voltage rating has higher ESR.

I dont know what to make of all this.

If confronted with a choice of voltage tarings for caps, should one get the higher rated caps, assuming the price difference is negligeable, as it is in the ERSE line of caps.

The highewr VDC rated ERSE caps cost pennys more then the standard 250 VDC ones.

[kg4guy]

I recently ordered some ERSE Poly Caps to re fresh my Cornwall 2's.

The ERSE Poly Caps are availiable in 250, 400, and 630VDC.

Initially, I ordered 250 volt caps.'

But, when I looked at the Red vs Blue Clarity Caps, I noticed Clarity Caps made a big deal that the more expensive Red Clarity Caps had a higher voltage rating,

So, I ordered the 400 and 600 volt version of the ERSE Poly Caps.

Then, I saw on Google that a thicker film cap with a higher voltage rating has higher ESR.

I dont know what to make of all this.

If confronted with a choice of voltage tarings for caps, should one get the higher rated caps, assuming the price difference is negligeable, as it is in the ERSE line of caps.

The highewr VDC rated ERSE caps cost pennys more then the standard 250 VDC ones.

This is a link that is of help http://www.humblehomemadehifi.com/Cap.html

[Al Klappenberger]

I just pulled two 30 Uf Solen FastCaps out of my collection of used caps and put them on my LCR meter. One is 250V and the other is 400V. The 400V cap did indeed have higher series resistance, but not by much. Both are good caps and were only used a little. I never thought about this before! Anyhow, the voltages levels in crossover networks is VERY low. 250V caps will give you plenty of safety margin.

Al K.

[ka7niq]

I just pulled two 30 Uf Solen FastCaps out of my collection of used caps and put them on my LCR meter. One is 250V and the other is 400V. The 400V cap did indeed have higher series resistance, but not by much. Both are good caps and were only used a little. I never thought about this before! Anyhow, the voltages levels in crossover networks is VERY low. 250V caps will give you plenty of safety margin.

Al K.

I bet even 100 volts would be fine, just wondered why the more expensive caps seem to have a higher voltage rating.

What do you think about capacitor break in AL

Ever measure an old mylar cap before ?

These new caps I put in the Cornwall 2's are a lot brighter and more vivid then the old Mylars.

NOT a hard sound, it just sounds like the squaker and tweeters level has been increased a bit ?

I THOUGHT Mylar Caps had a really long life, and did not go bad like electrolytics do ?

Assuming the old mylar caps in the cornwall 2's were not bad, why do I hear such a difference ?

I have been told that old Mylar caps get really high ESR as they age, maybe that is why I hear such a difference ?

The woofer cap called for a 68 uf, I used a 65uf, thinking that if I was going to make an error, I would rather the woofer roll offf a tad higher up, then have any hole where woofer and squaker meet.

The 68 uf cap in the cornwall 2 is a 10 percent cap, I used an ERSE 5 percent cap of 65 uf.

Al, from a theoretical standpoint, can the ESR of an aging Mylar cap be enough to attenuate the horns audibly ?

Comments ?

[kouack]

They are more expensive to produce and usually larger in size as the voltage increase for a specific capacitance.

[popbumper]

The cost relates to the amount of material used to net the rating (that is, the uF rating). The substrate is expensive, and it takes a lot of it to achieve the desired value.

The voltage rating, on the other hand, is a RESULT of the material amount used, not necessarily a goal. Because there is a lot of substrate used (the AREA increases), the voltage rating is increased.

Physical size means nothing. Take a small ceramic cap of 470pF, that has a 1000V rating. How can it be? The ceramic substrate has a much higher breakdown voltage, as opposed to a mylar cap of the same size. It's all about the substrate used, and the total area.

Chris

[Al Klappenberger]

I bet even 100 volts would be fine, just wondered why the more expensive caps seem to have a higher voltage rating.

I did a power analysis run on a crossover. Even with 100W input the maximum voltage anywhere in the network was about 30V RMS. This is a 8 ohm system. power = (E*E)/R = (30*30)/8 = 112W. A 250V cap has a 8 times safty factor!

What do you think about capacitor break in AL

I think it's a total myth. It's your brain getting used to a new sound. That's all!

Ever measure an old mylar cap before ?

Yes, even brand new ones have Q factors in the range of 200. Polypropylene caps are often 10 times better,

These new caps I put in the Cornwall 2's are a lot brighter and more vivid then the old Mylars.

Of course! The lower Q is resistive loss that kills the highs!

NOT a hard sound, it just sounds like the squaker and tweeters level has been increased a bit ?

Yes, same reason!

I THOUGHT Mylar Caps had a really long life, and did not go bad like electrolytics do ?

Electrolytics are the worst of all.

Assuming the old mylar caps in the cornwall 2's were not bad, why do I hear such a difference ?

Same reason again. They are lossey caps. igh priced paper-in-oil are jst as bad.

I have been told that old Mylar caps get really high ESR as they age, maybe that is why I hear such a difference ?

YEP!

The
woofer cap called for a 68 uf, I used a 65uf, thinking that if I was
going to make an error, I would rather the woofer roll offf a
tad higher up, then have any hole where woofer and squaker meet.

That's a 4.4% error. The cap you used is probably 5% at best and very likely 10%

The 68 uf cap in the cornwall 2 is a 10 percent cap, I used an ERSE 5 percent cap of 65 uf.

Al, from a theoretical standpoint, can the ESR of an aging Mylar cap be enough to attenuate the horns audibly ?

I'm not an expert on how parts age, but high ESR is not good and mylar caps have high ESR right out of the factory!

[deafbykhorns]

I would take a serious look at these caps, they perform very well in my homebrew Proac 1.5's. Checkout the DCR on the coils as well

http://www.northcreekmusic.com/Zen.htm

[khorn#1]

Al,

Forgive me for highjacking this thread but, What is going on with the ES network for Greg's vtrac? Is it still in the works?

Thanks,

Randy

[ka7niq]

I would take a serious look at these caps, they perform very well in my homebrew Proac 1.5's. Checkout the DCR on the coils as well

http://www.northcreekmusic.com/Zen.htm

Northcreek has a good reputation, I forgot they sold Caps too.

We must not forget the Sonicaps that Bob Crites sells, or the Solens either.

Northcreek suggests cascading caps, maybe a good idea ?

I MAY go back into the Cornwall 2's one day, mabe play with the caps again, just because it is so EASY!

I have the wooden crossover board in my pair of cornwall II's, and can solder, re solder at will.

THIS time, if I go back into the Cornwalls, I think I will order new MYLAR Caps, but just for the midrange.

And, I may series up some Mylar caps to intentionally get high ESR in the midrange.

At THIS point, not sure I LIKE the speakers the Cornwall 2's have become with the poly caps ?

Perhaps Klipsch WANTED the high ESR of the Mylar caps they originally gave the Cornwall 2's , to "tame" the drivers ?

I am getting a midrangy sound, at the moment, and I prefer a less foreward midrange, kinda like I had before I changed caps.

The sound I was getting with the old original mylar caps was maybe a little too laid back, especially on the tweeters.

I will leave the ERSE Poly Caps on the Tweeters, OR perhaps parallel some caps for the LOWEST ESR I can get, just for the tweeters.

[ka7niq]

I just listened some more, perhaps the caps are settling in ?

Hard to tell, lots going on here at home, haven't had as much time to listen as I would like.

I wish I knew the original sound character of a Cornwall 2.

Maybe this is how a Cornwall 2 is supposed to sound, and I liked some of the old Mylar Cap sound better, I don't know ?

Maybe with the new caps, the poor Cornwall 2's are just telling me they just dont LIKE my Yamaha RX V1 ?

My B&W 801's and my JBL S 412 P's sound just fine with the Yamaha.

I think the low ESR of the ERSE Poly Caps made the Cornwall 2's perhaps already foreward sounding midrange even more foreward.

Perhaps Klipsch engineers relied on the high ESR of the stock Mylar Caps to tone the mids down a bit, compared to what I have now ?

At THIS point, I find the Cornwall 2 a bit "on the edge" as far as the midrange goes.

I think the low ESR ERSE Poly Caps were not the best choice for the midrange application in the Cornwall 2, to my ears anyway.

It is my opinion the midrange needs a little more attenuation, so I am looking at some HIGH ESR Mylar caps, and I may even place 2 caps in series for even higher ESR if I have to.

I am also not crazy about this tweeters level, so perhaps I will parallel some ERSE Poly Caps in the tweeter circuit for Lower ESR then what I have now ?

My Cornwall 2's have the old wooden crossover board, so parts changes are a piece of cake with an electric screwdriver and a soldering gun.

I must play some more, because I like some things the Cornwall 2's give my system.

However, I am prepared for the possibility they just might not LIKE my Yamaha RX V1 ?

In that case, it will be time to lovingly say goodbye to them.

I am Married to the Yamaha DSP System, and my Yamaha RX V1.

Stay Tuned, as I attempt to re voice the Cornwall 2's to suit my tastes/system.

Maybe I just had some REALLY bad, old mylar caps, I don't know ?

My Ham Radio friends tell me Mylar Caps do NOT go bad, they just have high ESR, period!

Unfortunately, I tossed the old caps, wish I hadn't now.

I could simply have measured them, and found a new replacement, or knew for sure IF they were really "bad".

I THINK Radio Shack has Mylar Caps, perhaps I will start there ? http://www.radioshack.com/product/index.jsp?productId=2102515

I will need 3 of these in Parallel to make a 3uf Cap, but then it will have LOW ESR because resistance in parallel decreases, so I need to find me a 3uf Mylar cheapo with high ESR, and MAYBE (gasp) I will slap an electrolytic in there to REALLY get me some high ESR ?

Or, maybe I will take one of these http://www.radioshack.com/product/index.jsp?productId=2102479 and parallel it with the Mylar one above, that will give me 3.2 uf , but 1 is a 50 volt cap, the other 250vdc, anyone know what the combined voltage rating will be ?

I know it is a "sin" to use an electrolytic cap, and to mix an electrolytic with a mylar (Gasp), but I need to see for myself!

I have had several pairs of great sounding speakers with nothing but electrolytic caps in them, or Mylar.

I am starting to think the engineers took the type of caps they originally used into account, high ESR and all ?

And, putting a lower ESR cap in aint always better!

Different, yes, better, that is a matter of opinion.

I will check local car stereo stores first for a 3uf mylar.

I think I am learning about capacitors, LOL

It is all about ESR and Capacitance value.

Off hand, does anyone know if Electrolytics have higher ESR then Mylar ?

Now I SEE why horn people love old Paper In Oil Caps, LOL

No "magic" here.

Those old caps have such high ESR they attenuate the horns.

Decisions, Decisions, Decisions !!!!!

[hklinker]

You might want to consider Sonicaps, which Bob Crites sells or you can buy direct from Sonicraft.

They are more expensive than Jantzens or Daytons, but much less than Mundorfs and about half of Auricaps. If you go to the Sonicraft website they have an explanation of how their Gen I and Gen II caps can be bundled to produce a very smooth and balanced sound.

I just replaced the crossovers in my Cornscalas with this configuration. You pair a larger value Gen I cap to a smaller value Gen II with the Gen II shorter lead (shield) upstream. I was very happy with the results. I have spent about a week now listening to them and find that there are three significant improvements. First, the image drift I noticed previously was gone. I don't know what caused it in my other Xovers but it was noticeable. Second, there was a big improvement in the tweeter, which I thought was acceptable, but not remarkable, previously. The CT-125's really stand out now. Finally, both the squawker and tweeter seemed more open and had a much greater clarity than before. Cymbals are crystal clear and crisp, percussion like woodblocks and cowbell have a much greater depth and resonance. Horns, particularly the tenor sax and muted trumpet, sound incredibly realistic.

I really like what these caps have done to improve my Cornscalas. Check 'em out

Herb

[ka7niq]

You might want to consider Sonicaps, which Bob Crites sells or you can buy direct from Sonicraft.

They are more expensive than Jantzens or Daytons, but much less than Mundorfs and about half of Auricaps. If you go to the Sonicraft website they have an explanation of how their Gen I and Gen II caps can be bundled to produce a very smooth and balanced sound.

I just replaced the crossovers in my Cornscalas with this configuration. You pair a larger value Gen I cap to a smaller value Gen II with the Gen II shorter lead (shield) upstream. I was very happy with the results. I have spent about a week now listening to them and find that there are three significant improvements. First, the image drift I noticed previously was gone. I don't know what caused it in my other Xovers but it was noticeable. Second, there was a big improvement in the tweeter, which I thought was acceptable, but not remarkable, previously. The CT-125's really stand out now. Finally, both the squawker and tweeter seemed more open and had a much greater clarity than before. Cymbals are crystal clear and crisp, percussion like woodblocks and cowbell have a much greater depth and resonance. Horns, particularly the tenor sax and muted trumpet, sound incredibly realistic.

I really like what these caps have done to improve my Cornscalas. Check 'em out

Herb

Glad it worked out for you!

I found these charts http://my.execpc.com/~endlr/esr.html

And http://my.execpc.com/~endlr/aging.html

My Ham Radio Friends were correct, Mylar Caps do NOT "age", as can be clearly shown by the charts.

The "high ESR" claimed by "aging" is inherent in the Mylar Cap.

HOW can a capacitor "increase in ESR" and not lose capacitance ?

As can be seen from the chart, 1 percent is the most capacitance deviation in the life of the Mylar cap.

You tell me HOW can a cap "gain esr" and not lose capacitance ?

I think the "difference' we hear when changing caps is all about ESR.

The sonicaps are low ESR caps, good ones no doubt, designed for the cornscala, and their ESR taken into account in the design perhaps?

My Cornwall 2's need some higher ESR caps IMHO on the midrange, like they originally had.

I see now that electrolytics have even higher ESR then Mylar, so I think I will start there, and move up to mylar if needed for reduced ESR compared to electrolytic.

JUST on the midrange 3uf crossover.

[Guest David H]

My Cornwall 2's need some higher ESR caps IMHO on the midrange, like they originally had.

I see now that electrolytics have even higher ESR then Mylar, so I think I will start there, and move up to mylar if needed for reduced ESR compared to electrolytic.

JUST on the midrange 3uf crossover.

I am confused, why would you want a higher esr cap on the mids? Electrolytics are not good for crossover use, Poly caps like the Sonicaps are a far better choice.

I went back and read your post, seems the mid is too hot for your liking, but using inferior capacitors is not going to solve the problem.

Dave Harris (N3DH)

[hklinker]

Hi Dave!

As I said above, I am loving the new Xovers. I think you hit a homerun with your design! I am hearing all kinds of sublteties I never heard before and I really like the 400/600 option, as well as the tweeter attenuator. I may have to back off the tweeter 3 db in fact as it really has jumped out with the new Xover. Not sure if the GenI/GenII pairing made the difference, but who cares as there is a BIG difference!

ka7niq, Dave has designed both my crossovers and his suggestions have proven invaluable. There are several crossover "gurus" on this forum so I know that your will get your issues resolved.

Herb

[ka7niq]

My Cornwall 2's need some higher ESR caps IMHO on the midrange, like they originally had.

I see now that electrolytics have even higher ESR then Mylar, so I think I will start there, and move up to mylar if needed for reduced ESR compared to electrolytic.

JUST on the midrange 3uf crossover.

I am confused, why would you want a higher esr cap on the mids? Electrolytics are not good for crossover use, Poly caps like the Sonicaps are a far better choice.

I went back and read your post, seems the mid is too hot for your liking, but using inferior capacitors is not going to solve the problem.

Dave Harris (N3DH)

Dave, in my Cornwall 2's were the stock Mylar Caps.

I changed them to the low ESR ERSE Polycaps, now the mids seem too hot.

My resoning is that the old mylar caps had higher ESR, and that gave the more laid back sound vs the midrange foreward sound of the low ESR ERSE Polycaps.

The ERSE Polycaps are good caps.

I have used them before in some other speakers, with great results.

Just not this time.

At least not on the 3uf Cornwall 2 crossover cap.

The old Mylar Caps were just too laid back sounding, the new ERSE poly cap is too foreward, telling me that I need a cap with ESR value in the middle of these two caps.

OR, perhaps the caps just need to break in ?

OR, the ERSE Polycap is making the Cornwall 2 what it once was again, and the poor Cornwall 2 is simply "crippled" by being hooked up to a Yamaha receiver ?

Dave, you are a Ham I see !!!!

I have many electronic toys, but only 2 that I would "shoot you over" if you decided to "steal them" LOL

One is my Kenwood TS 850 S Ham Radio Transceiver, and one is my Yamaha RX V1

I simply adore the Yamaha DSP System, and my room is arrayed with the full blown Yamaha DSP speaker set up, complete with Yamaha DSP front effects speakers.

The Cornwalls must work in this audio/video system, with the Yamaha RX V1.

I have B&W Matrix 801's in my audiophile system in a seperate, smaller room.

Since the capacitor life span table I posted shows a Mylar Cap only loses 1 percent of its capacitance as it ages, what else besides ESR can be effecting the sound ?

The ERSE Caps are well regarded, even used by several speaker manufacturers like Thiel and GR Research, to name but a few.

I have had great results with them in the past, just not this time.

Unless I AM getting great results, and the poor Cornwalls just dont like the Yamaha RX V1 ?

[ka7niq]

For the sake of this thread, I am posting this info I found about different capacitor types.

The aging info of a Mylar Cap I bolded below, and is typically 1 percent over the life of the Mylar Capacitor.

AN INTRODUCTION TO CAPACITORS

by David Johnson, Los Banos, CA.


Inexperienced techs, and engineers fresh out of school, frequently
assume that once you know the value of a capacitor you know almost
everything there is to know about it that's important. After all,
this rule of thumb works with resistors most of the time. But there
are very important differences between the various types of
capacitors-- which is the reason that so many different types are
marketed. I will discuss the important properties of the more common
types of capacitors that you are likely to encounter. This discussion
will not cover specialty capacitors.

ALUMINUM ELECTROLYTICS pack a lot of capacitance into a relatively
small volume, and are cheap. They are used primarily for power-supply
filtering, low-frequency AC coupling, and DC blocking. In general
they are not suitable for other applications because they have very
sloppy tolerances, exhibit marked temperature drift, have low Q,
require DC biasing of known polarity (except special nonpolarized
units), and have high leakage currents, especially if the capacitor
has not been used for a long period of time. If biased with the wrong
polarity of DC voltage, they usually explode within several seconds or
minutes, creating a substantial hazard. Aluminum electrolytic
capacitors gradually deteriorate with age, though this problem is not
a serious one with modern units. Never use old or surplus
electrolytics-- buy new; they're cheap. Aluminum electrolytics give
best life and performance when used at close to their rated voltage.
Don't use a 100 volt unit in a 10 volt circuit. A 16 volt unit would
be much better. Aluminum electrolytics are widely available in
ratings from 1 to 10,000 microfarads (uF), with voltage ratings up to
several hundred volts in the low to medium capacitance ranges.

SOLID TANTALUMS. These are solid semiconductor electrolytics with
properties that are generally better than aluminum units. They are
widely used for power-supply decoupling and low-frequency AC coupling.
They are much more stable with time and temperature than are aluminum
electrolytics, and have higher Q as well. It's OK to use them at
voltages much lower than their rating, but they _are_ polarized and
should never be allowed to become reverse-biased. A reverse-biased
solid tantalum may work for seconds to several days, but it _will_
fail, usually with a horrible stench and possibly fire. Solid
tantalums are sometimes used in non-critical timing and frequency
filtering circuits. Solid tantalum capacitors are widely available in
ratings from 0.47 to 47 microfarads at up to 35 volts in the lower
capacitance values.

POLYESTER (Mylar ) FILM CAPS. These popular capacitors are widely
available in ratings from .001 to 10 uF, at voltages up to 630 volts
in the medium and low capacitance values. They receive use in a wide
variety of applications, particularly in audio-frequency circuits.

Their temperature curve is fairly flat at room temperature, providing
good stability when used in equipment that will not be used outdoors.
Aging is generally less than 1% over the life of the product. Q
factor is several hundred at audio frequencies, but plummets at higher
frequencies, making them generally unsuited for RF work. Dielectric
absorption and DC leakage preclude their use in high-performance
sample-and-hold circuits.

POLYCARBONATE FILM CAPS are rather similar to polyester caps, but most
of their electrical properties are better. The temperature curve is
relatively flat over a much wider range and is generally within the
range of +25 to -50 ppm per degree C at room temperature. Q is about
1000 in the audio range, dropping to about 100 at 1 MHz. Dielectric
absorption and leakage are low enough to allow use in medium-
performance sample-and-hold circuits. Polycarbs are bulkier than
polyesters for a given capacitance and voltage rating, and they cost
more. They are available in tighter tolerances (1%) than polyesters,
and they generally age less than 0.2% over the life of the product.
Polycarbs are manufactured in the same capacitances and voltage ranges
as polyesters, but are not as widely available as polyester since they
are more costly. Probably the most common uses for polycarbs are
high-Q audio filters, tight-tolerance RC timers, and precision
instrumentation circuits.

POLYPROPYLENE FILM CAPS. Somewhat similar to polycarb, but reserved
for even ore critical applications. Aging is generally less than 0.1%
over the life of the product, dielectric absorption and DC leakage
specs are even better, and Q is several thousand in the audio-
frequency range. The temperature coefficient is fairly steep-- about
-220 parts per million per deg. C.-- but the curve is flat, making it
possible to use other components to compensate for temperature drift
over a wide range if that is necessary. Polypropylene film caps are
used to some extent in lower frequency RF work, where positive tempco
inductors can be used to balance the tempco of the capacitor to
produce a very stable tuned circuit. Polypropylene caps are generally
available in the range of 470 pF to 1 uF, up to 630 volts, are harder
to find than polyesters and polycarbs, and are more expensive and
bulkier than polycarbs. Digi-Key sells 2% tolerance units and most
manufacturers have 1% tolerance units available. Most usage of
polypropylene caps is in high-performance tuned circuits, timers, and
sample-and-hold circuits; however, they are starting to see use in
switching power-supplies because their high Q allows them to handle
large amounts of power without overheating or reducing efficiency.

POLYSTYRENE FILM CAPS. Extremely low dielectric absorption and DC
leakage make this a popular capacitor for high-performance S/H
circuits and integrating A/D converters. Its superb stability (ageing
typically less than .05% over life) and predictably low temperature
coefficient (-150 to -190 ppm per deg. C) over a very wide temperature
range make this a common capacitor in high-performance
instrumentation. Its extremely high Q (over 10000 in the audio range,
and several hundred at 1 MHz) make it popular for lower-frequency RF
tuned circuits. Readily available in values from 100 pF to .01 uF--
Higher values are difficult to find, and they are very bulky.
Polystyrene caps are very easily damaged by heat from soldering, and

by solvents. Because of this, polystyrene capacitors are losing
popularity (primarily to polypropylenes and to NPO ceramic
capacitors).

EXOTIC PLASTIC-FILM CAPS include Teflon , polysulfone, parylene
and other dielectrics. These are generally available only on special
order from the factory, and they aren't used except when nothing else
will do. The exotics generally exhibit some combination of high
stability and/or operation at high temperatures.

CERAMIC CAPACITORS. These are even ore diverse a group than the
plastic film capacitors, and are even less interchangeable. When you
buy surplus or used ceramic caps, you usually don't know what kind you
are getting. If you don't know what kind they are, don't buy 'em.

NPO (COG) CERAMICS. These are very stable with time and temperature,
and have high Q at RF. Temperature coefficient is les than +-50
ppm/deg.C and ageing is extremely low. Widely available in values
form 5 pF to 1000 pF (and less widely available 1 to 10000 pF) in two
popular styles: disc and multilayer. The multilayers are more
compact in the larger capacitance values. A tubular style used to be
popular but is rarely seen anymore. When handling and soldering
ceramic capacitors of any type, use care-- the leads on some
manufacturers' units are poorly bonded to the capacitor plates, and
detach easily. On some, the attachment solder melts at a temperature
lower than that of ordinary solder, so if in doubt, use pliers as a
heat-sink on the leads. If the wire _does_ detach, the protective
coating will often hold it in place, leaving an open or intermittent
capacitor that looks physically perfect. NPO capacitors are widely
used in RF circuitry. They are gradually displacing micas in most
applications because they have higher Q and better stability than most
micas. In addition, the multilayer NPO's are much smaller than micas.

X7R CERAMICS. These are designed for general-purpose use where
stability is not critical. A rather wobbly temperature curve keeps
capacitance variation due to temperature change within +-5% of room
temperature value from -40 to +90C. Capacitance can decrease up to
several percent with aging. Initial tolerance is generally 10 or 20%-
- tighter tolerances are not available because aging effects would
make tighter tolerances meaningless. Three styles are popular-- disc,
multilayer, and military CK05 box style. Popular values range from
.001 to 0.1 uF; lower and higher values are available. Polyester film
caps are gradually displacing X7R ceramics in many applications;
however, where space is critical, multilayer X7R's can still beat
polyester film caps for size.

Z5U CERAMICS. These are used almost exclusively for power-supply
bypassing. Their capacitance changes markedly with temperature, and
there is an appreciable capacitance loss with aging. Both disc and
multilayer styles are popular, and values from .01 to 2 uF are readily
available. The multilayer type can be smaller than an aluminum
electrolytic of the same capacitance. Z5U's have lower impedance at
high frequencies than do electrolytics, and do not require a DC bias
voltage since they aren't polarized. Because of these reasons, they
are more popular than aluminum electrolytics in values below 1 uF.


TEMPERATURE-COMPENSATING CERAMICS are generally similar to NPO
ceramics, but are designed to have a specified negative temperature
coefficient. They are hard to find, and are used primarily for
temperature compensation of other components such as inductors or
quartz crystals at RF.

REDUCED TITANATE (BARRIER TYPE) CERAMICS. Not used much anymore.
This group comprises a wide variety of temperature coefficients and
capacitance values. They require DC polarization, have low voltage
ratings (as low as 3 volts), have extremely high leakage. They met a
need for small capacitors in the early days of the transistor, before
modern multilayer ceramics were developed.

OTHER CERAMICS. There are other ceramic types available, the most
popular of which are probably formulations designed to get more
capacitance per unit volume for power-supply bypassing applications.
These formulations are generally less stable than Z5U and should be
used only for power-supply bypassing. Values up to about 10 uF are
available.

MICA CAPACITORS have a low temperature coefficient, good stability,
and high Q at radio frequencies. However, the performance of NPO
ceramics is in general slightly superior, and the NPO's are usually
cheaper and smaller as well. Mica capacitors are readily available in
values from about 3 pF to several thousand pF. They are still a bit
easier to obtain in tight tolerances (to 1%) and high voltage ratings
than are NPO's.

PAPER CAPACITORS used to be _the_ general-purpose capacitor, but have
been almost entirely superseded by polyester and ceramic capacitors.
They are still used to some extend in applications involving AC line
power, for instance, motor-starting capacitors. The paper is normally
impregnated with an oil or some other material that is the actual
dielectric.

FILM VARIABLE CAPACITORS. These are the little plastic variable
capacitors in modern portable radios. The dielectric is a plastic
film-- polyethylene, I think, but possibly something else. The
temperature coefficient is probably about -200 ppm/deg C, which
compensates a tuning inductor having a tempco of +200 ppm. Installing
a proper knob on one of these (or even installing it, period) can take
some ingenuity or access to rare hardware. Sometimes good hardware
can be cannibalized from a junked receiver.

AIR VARIABLE CAPACITORS. More stable than the film variables, and
available in a much wider range of voltages, capacitances and styles.
Unfortunately, there are few manufacturers still in business, and
prices of new units are quite high. Experimenters usually obtain air
variable caps through surplus houses or by cannibalizing old
equipment. The high voltages encountered in most transmitters
preclude the use of film variable caps. Many air variable caps come
with a 1/4 inch diameter shaft, making it easy to install a knob or
other hardware. Maximum capacitance available is about .002 uF.


VACUUM VARIABLE CAPACITORS withstand very high voltages, and are used
in the power and antenna circuits of radio transmitters. They are
very expensive, generally over $200 if purchased new. Experimenters
usually obtain them from surplus houses or by cannibalizing old
equipment.

TRIMMER CAPACITORS. These are designed for set-and-forget, not to be
frequently adjusted like the other variable capacitors discussed.
Popular types are rotary )air, film or ceramic dielectric), and mica
compression types. Air types are most stable, and generally most
expensive. Film and ceramic types often have rather high temperature
coefficients. Mica compression type has low temp. coefficient, but is
prone to come out of adjustment by itself. The mica compression type
is available in maximum values up to 2000 pF, ceramic and film types
up to about 150 pF, and air type to about 60 pF.

DOUBLE LAYER "MEMORY BACKUP" CAPACITORS. These devices have
electrical properties intermediate between an electrolytic capacitor
and a rechargeable battery. Nominal capacitance values range from
about .02 to several Farads. They must be used at about their rated
voltages (which is usually 5.5 volts). They are used to provide power
backup to CMOS memory for up to several hours in the event of a power
outage. I am not aware of any other use for these "capacitors."


Frank Reid W9MKV

[freddyi]

What's the useful life active or shelf for Mylar vs polypropylene? (at what point from manufacture do they need replacement?) - do those lifetimes vary due to the conditions where they were made and air quality issues where they're used? Do the metallized variety differ much with regards to quality of their lead termination? Do foil types generally have superior lead termination? Do copperweld leads sound different than pure copper leads? Can caps which measure the same for capacitance and ESR be told apart? On a crossover does the material where nodes connect matter with regards to audible consequences? - say steel terminal strip or lug vs direct soldering of leads? - whats the best compromise for tying the nodes? Can crossover wiring inductance and long runs to tweeter play any role at tweeter frequencies vs ESR? Do caps exhibit variance in microphonics? - if so can anything be gleamed from connecting a cap to a high gain amp and tapping it while listening or reading its spectrum on a RTA freeze? - or it that meaningless in crossover application? re: - your ERSE - could a fractional ohm resistor in series with your cap tune the tone where you might like it? - or does the cap have an inherent property that's not easily described nor adjusted?

[Guest David H]

I changed them to the low ESR ERSE Polycaps, now the mids seem too hot.

I see, still I would run them for a bit, and see if your ears or caps break in. I have seen many threads where 30ppi open cell foam is inserted in the horn to soften the sound when used with SS gear.

Although sceptic I tried the foam on a pair of stock cornwalls with metal horns, and found the results to be positive. The foam is filter foam, and used by speaker manufactures like Mcintosh for speaker grills, and over microphones as wind screens.

Foam is also used on these speakers.

http://www.gedlee.com/

[ka7niq]

What's the useful life active or shelf for Mylar vs polypropylene? (at what point from manufacture do they need replacement?) - do those lifetimes vary due to the conditions where they were made and air quality issues where they're used? Do the metallized variety differ much with regards to quality of their lead termination? Do foil types generally have superior lead termination? Do copperweld leads sound different than pure copper leads? Can caps which measure the same for capacitance and ESR be told apart? On a crossover does the material where nodes connect matter with regards to audible consequences? - say steel terminal strip or lug vs direct soldering of leads? - whats the best compromise for tying the nodes? Can crossover wiring inductance and long runs to tweeter play any role at tweeter frequencies vs ESR? Do caps exhibit variance in microphonics? - if so can anything be gleamed from connecting a cap to a high gain amp and tapping it while listening or reading its spectrum on a RTA freeze? - or it that meaningless in crossover application? re: - your ERSE - could a fractional ohm resistor in series with your cap tune the tone where you might like it? - or does the cap have an inherent property that's not easily described nor adjusted?

GREAT Questions Freddy.

I am still learning, but I am starting to believe there are rational reasons a cap sounds different.

For instance, I just read that the Q of a crossover slope is effected by ESR.

Crossover induced Q change can certainly be audible.

Low ESR may be theoretically "better", but our ears are not a test bench.

Personally, I think the woofer in the Cornwall 2 may need to play UP in frequency just a little higher, the way I currently have them.

But this may because of the lower ESR ERSE Caps I used ?

I Think I am gonnna just leave the crossovers hang out the bass reflex holes in the Cornwall 2, if I can, even if it means adding some extra wire, temporary.

That way, I can voice them as I see fit!