The light dawns on Film vs NPE’s and ESR’s

transmaster said:
Do you know the year thus white paper was posted the North Creek Music website is archived at Internet Archives.
https://web.archive.org/web/collections/*/www.northcreekmusic.com

It show be there if so the is something that need to be pinned here someplace to keep it available.
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Genius...! I always forget about Wayback.

North Creek Bypassing

"The Art of Bypassing


Bypassing capacitors is a little like blending watercolors. With watercolors, the dominant pigment can be brightened, softened, darkened or lightened with small additions of other hues, and it takes a delicate touch to make the perfect shade.

With capacitors, the signature of the base cap can be brightened, softened, darkened or lightened with the addition of the appropriate choice of bypass capacitor. The "perfect" tonal balance can only be determined by ear.

And, like watercolors, the whole is often greater than the sum of its parts.

The bypass capacitors we have developed have very specific subjective characteristics that can be applied to improve the performance of most loudspeaker crossover capacitors significantly:



Cascade Bypassing

Classically, bypassing a capacitor means paralleling a very small cap (0.5% to 1% of the base cap) to improve the effective high frequency performance of the base cap. While this works to a point, the problem with simple bypassing it that it tends to sound a little discontinuous, with the large cap dominating the signature at the low end while the bypass cap dominates the upper extreme.

Cascade Bypassing (or simply "Cascading") is a bypassing method that yields the best and most homogeneous sounding combination of capacitance. Cascading is essentially paralleling smaller and smaller capacitors of increasing voltage to reach the target value. We usually suggest a cascade of 5% to 25% steps, with each smaller cap having a higher voltage rating.

An example of a Cascade is creating a 4.7µF cap from a 4.0µF 200V, 0.47µF 600V, 2 x 0.10µF 600V.

100.0µF = 100µF 100V + 5.0µF 225V +1.0µF 625V (=106µF, within 10% of 100µF)

10µF = 6.0µF 200V + 3.0µF 200V + 1.0µF 600V + 0.10µF 800V

or 10.0µF 200V + 0.47µF 600V + 0.047µF 800V

5.0µF = 5.0µF 200V + 0.22µF 600V + 0.047µF 800V

3.3µF = 3.0µF 200V + 0.22µF 600V + 0.10µF 800V

Cascading sounds better than simple bypassing because it yields an overall homogeneity to the sound of the equivalent capacitor.



Bypassing with North Creek Capacitors

Harmony Capacitors were designed specifically to bypass other metallized capacitors. Their signature is lightweight with a wealth of detail, and the top end has a nice sparkle without being bright or forward. They are also much quieter than most capacitors, particularly those that wound with very high tension. We best describe the Harmony caps as "cleaning up the sound" of other capacitors.

Crescendo Bypass Capacitors were designed to correct the harmonic imbalance we found in most of the film capacitors coming out of California; that is, a weak lower midrange, forward upper midrange and over-emphasized treble.. Many listeners equate this tonal imbalance with a "wealth of detail", although we find it unnatural and unsatisfying for long term listening. The Crescendo bypass cap, with the thick 600 Volt and 800 Volt film and heavy conductor, is very rich through the midrange and much softer in the top end than most of the "West Coast" designs. In designs where both the tweeter and the electronics tend to be bright, but a "wealth of detail" is a primary design goal, the combination of a "West Coast" capacitor with a Crescendo bypass capacitor usually yields the best of both worlds.



Unusual Qualities of the Crescendo Capacitor

We have noticed some of the strangest things can occur when one bypasses with a 1.0µF crescendo capacitor.

Perhaps the most unusual is the way this cap can "quiet down" a woofer when used in the capacitor stack going from the output of the low pass input coil, to ground. This is true of both Zobel circuits and shunt legs of second or higher order low pass filters. Frankly, we can not pin down why this effect is so dramatic in a parallel application, but it is. Try it - you'll like it. It may even blow you away.

We have heard of several customers using five 1.0µF 600V Crescendo caps bypassed with a single 0.10µF 800V crescendo to drive a Focal T120 tweeter. This is a driver with excellent information retrieval but when used with the wrong caps tends to get a little brittle. The stack of Crescendo caps is said to yield the ultimate combination .

For those using the Scan Speak Revelator tweeter, one should cascade Crescendo caps throughout. The Revelator has a broad peak in the 8kHz to 20 kHz region that will be emphasized considerably by any of the brighter film and foil caps available. Make no mistake - this may be the best tweeter in history, but it needs proper care and feeding to sound its best. See our Rhythm-Revelator project for more information."
 
RTally said:
I was hoping for a technical paper, or at least something that described a measurable effect. Maybe some double-blind listening tests. Instead, that white paper reads like advertising hype. It contains no information other than what they recommend for selling their caps.
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+1
 
As for the sound of different capacitors in general I'll put forward two theories which may account for the differences, though more as food for thought rather than a dogmatic assertion that I'm right:

1) Capacitors are sensitive to vibration. This effect is used to make capacitor microphones in which one plate of the capacitor is made to be extremely sensitive to vibration and the modulation of the capacitance between the plates is used to sense the vibration and turn it into a voltage. Of course, they're intended to be vibration-sensitive, but even capacitors which aren't can still be sensitive. In very high gain circuits such as MC phonostages the effect can be detected by simply tapping the circuit board and listening for anything audible. You might be surprised by how much you can hear it. Loudspeaker crossovers have no gain at all, but the SPLs inside a loudspeaker cabinet can be very high and any components inside will be subjected to considerable vibration. It would make sense therefore to use capacitors with tightly wound foil and which are encapsulated in a thick and tough epoxy coating.

2) The other effect is voltage modulation of the capacitor. When a capacitor is charged the two plates experience an attractive force which will tend to pull them together. This effect can be seen on electrostatic speakers - when the polarizing voltage is switched on the flexible membrane is visibly pulled tight towards the backplate. Pulling the plates closer together makes the capacitance go up. An AC voltage applied to a capacitor will produce a continuously varying force on the two plates and if the plates can move at all will also produce modulation of the capacitance. To mitigate this it makes sense to have the two plates and the dielectric between them be as rigid as possible. Again, capacitors which are tightly wound and well encapsulated would make sense.

If there's any truth in theories 1) and 2) the physical construction of the capacitors matters as much as anything else. If higher voltage capacitors have any merit, could it be due to the use of thicker/harder dielectric materials and thicker/stiffer plate materials?
BTW, these aren't theories which I have just dreamed up. I must give credit to the late Cyril Bateman for his work in this area. He was the real expert.
 
In my case I don’t care if it works or not. I figure a cheap experiment. What rather irritates me is the blanket statement that NPE’s are crappola. The Mundorf E-Cap’s are really good in my W35’s and W45’s I am going to put my instruments on the combination and see what might be going on. A lot of the stuff that is being claimed is true but at RF frequencies.
 
Your microphonic capacitor observation might have some merit. If you look at a plate amp for a subwoofer there is a lot potting goo holding things down it is the semi flexible stuff that would dampen vibration. The electronics are in an environment of low frequency SPL especially in a sealed subwoofer design.
 
StimpyWan said:
Also, a respected speaker designer, on the same site, mentioned that he likes and uses bypass caps. He stated that bypass caps have the benefit of increasing the discharge rate of the cap it's in parallel with. This helps speed up the sound of the circuit, helping transient response.
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It's the other way around- the larger cap slows the time to discharge or charge the pair. Adding more capacitors in parallel, no matter what kind they are, only increases the total capacitance and thus the time to charge or discharge. Don't believe me? Take one of your big NPE's, charge it up, then discharge it into a resistor while measuring voltage. Use a resistor of size appropriate for a couple minutes to measure with a stopwatch if that's what you have. Then put the bypass cap across, and clock the discharge time again. Report back with the astounding speed increased caused by adding a bypass cap.

transmaster said:
Now capacitor charge memory is something that was discussed in one of the Audioholic Youtubes. They said that anything that reduces this charge hangover will improve the sound and can better protect the tweeters.
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Any "hangover" would manifest as a phase shift. The real question would be if the "hangover" changes with voltage or frequency. Easy enough to measure, can you point to any measurements?

Dielectric memory/relaxation can be a real thing (and I once had an extremely load experience with it from a pair of 100uF/4kV photo-flash capacitors). But the time constant for that effect is in minutes, not milliseconds. Certainly not fast enough to matter to a tweeter.

This makes since to me the QSK circuits in HF amplifiers use thing like flyback diodes to quickly, in a fraction of a second, go from 1000watts input to Zero, and back again.
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There's a lot of differences between a PIN diode used as a RF switch by changing the bias, and a small bypass cap used at audio frequencies in a speaker crossover. But one thing they share in common is that neither will improve the audio performance of a much larger cap that they are paralleled with, and which will still dominate the overall audio response.
 
This is going to be interesting the Gen II Sonicap’s are on sale so I saved a couple of bucks on each one.

I am not expecting anything.

I am going to take the opportunity to replace the internal speaker wires. The wiring is 50 years old and the insulation is rather stiff. The speakers are soldered which makes it a delicate job getting the speakers disconnected. I just cut the wires. The existing wire is 24 AWG. I am going to replace it with Silicone insulated 20AWG stranded wire. This is my standard hook up wire used in my old portable AA5 it is very flexible. I resisted the urge to get Jupiter cryogenically treated silk insulated 28 AWG hookup wire at $1.12 a foot.
 
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fill35u said:
Which means, despite it's perfect lack of ESR or inductance, it's still a perfect *capacitor*, and its impedance still depends on only two things: its capacitance value and frequency. At any given audio frequency, the bypass cap's impedance will always be much higher than the impedance of the NPE cap with its much higher capacitance, despite the NPE possibly having significant ESR.
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Actually, that's not all that's going on, at all.

One flaw of electrolytic caps, is that due to the long length of wound electrode, they have significant INDUCTANCE compared to film caps. Due to this inductance, the E-cap will actually have a higher-than-ideal impedance at high frequencies- and in fact, due to that inductance, there can be cases where the larger E-cap will have higher impedance at HF than a smaller film cap. At this point, the performance of the E-cap will be improved, at high frequencies, by the presence of the small film cap...

Regards,
Gordon.
 
GordonW said:
One flaw of electrolytic caps, is that due to the long length of wound electrode, they have significant INDUCTANCE compared to film caps.
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I don't think so. A film cap with the same capacitance as an electrolytic has a much longer length of wound conductor, hence the bigger size.
 
GordonW said:
Actually, that's not all that's going on, at all.

One flaw of electrolytic caps, is that due to the long length of wound electrode, they have significant INDUCTANCE compared to film caps. Due to this inductance, the E-cap will actually have a higher-than-ideal impedance at high frequencies- and in fact, due to that inductance, there can be cases where the larger E-cap will have higher impedance at HF than a smaller film cap. At this point, the performance of the E-cap will be improved, at high frequencies, by the presence of the small film cap...

Regards,
Gordon.
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Gotta disagree on this one, unless by higher frequencies you are referring to RF, in which case there is no impact for speaker crossovers. Effective series inductance (ESL) at audio freqencies is virtually nil. ESL is an issue at high frequencies (RF), not audio frequencies.

At low (audio) frequencies, capacitor impedance is primarily a function of the capacitance value and ESR. At higher (radio) frequencies, ESL contributes to a capacitor's impedance, with the ESL contribution increasing as the frequency increases above audio frequencies. This is illustrated in the following figure from a Mouser Technical Note for electrolytic caps.

Fig 14 Cap impedance curve.png
https://www.mouser.com/pdfDocs/UCC_ElectrolyticCapacitorTechnicalNotes.pdf

rothwellaudio said:
I don't think so. A film cap with the same capacitance as an electrolytic has a much longer length of wound conductor, hence the bigger size.
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It all depends on the cap construction. Some manufacturers build their caps to minimize parasitic inductance (ESL), for example, Vishay. Those same techniques can be used for modern electrolytics and film type caps. Typically low ESL is desirable for caps in circuits used above 10 MHz.
 
What is really irritating about Mundorf is that don’t have data sheets for their capacitors. Mundorf does not make any ridiculous claims for the sonic qualities of their capacitors just how well constructed they are. I will be real surprised if I hear any difference. But I am going to replace the internal speaker wire I want longer wires to facilitate any servicing I might need to do in the future.
 
RTally said:
Gotta disagree on this one, unless by higher frequencies you are referring to RF, in which case there is no impact for speaker crossovers. Effective series inductance (ESL) at audio freqencies is virtually nil. ESL is an issue at high frequencies (RF), not audio frequencies.

At low (audio) frequencies, capacitor impedance is primarily a function of the capacitance value and ESR. At higher (radio) frequencies, ESL contributes to a capacitor's impedance, with the ESL contribution increasing as the frequency increases above audio frequencies. This is illustrated in the following figure from a Mouser Technical Note for electrolytic caps.

View attachment 1672678
https://www.mouser.com/pdfDocs/UCC_ElectrolyticCapacitorTechnicalNotes.pdf



It all depends on the cap construction. Some manufacturers build their caps to minimize parasitic inductance (ESL), for example, Vishay. Those same techniques can be used for modern electrolytics and film type caps. Typically low ESL is desirable for caps in circuits used above 10 MHz.
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It also depends on the value. Electrolytics are found in up to hundreds of microfarads- at those capacitance values, the length of the winding DOES cause inductance to have some significant value- enough so, that engineers such as Greg Timbers of JBL, among others, found reason to bypass electrolytic caps on a regular basis, in their higher-line speakers.

IIRC, Greg found that the addition of a film cap bypassing an electrolytic, could cause an increase in the Q of the crossover- which has some effect on how fast, and how far down in level, that a crossover will filter a driver... that can be a significant effect sonically.

Also remember- in the day that most of the speakers in question were made (1970s to early 1990s), the electrolytic caps were far worse in performance than what's available now. What required a bypass cap to have "adequate" performance then, may not require one noe...

Regards,
Gordon.
 
transmaster said:
What is really irritating about Mundorf is that don’t have data sheets for their capacitors. Mundorf does not make any ridiculous claims for the sonic qualities of their capacitors just how well constructed they are. I will be real surprised if I hear any difference. But I am going to replace the internal speaker wire I want longer wires to facilitate any servicing I might need to do in the future.
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Mundorf E-Caps and Jantzen Audio Premium Elko NPE's are both made by FTCAP in Germany. Maybe you can find more info there. So while it appears the NPE's are outsourced, both companies hand wind their film caps themselves.
 
What I found interesting about the original Minerva NPE’s in the Wharfedales is they were always spot on micro Farad wise it was their ESR’s that were sky high.
 
Glad I haven't tossed all the caps I pulled from speakers. Since acquiring a DER EE DE-5000 I've been doing a lot of testing. Additional data to compare to what a couple mega328's and a couple of flukes were providing.
Also somewhat surprised by the caps pulled from my Sony TAN-5550. Starting to doubt that "new" caps are automatically superior to old caps.

YMMV
 
GordonW said:
It also depends on the value. Electrolytics are found in up to hundreds of microfarads- at those capacitance values, the length of the winding DOES cause inductance to have some significant value- enough so, that engineers such as Greg Timbers of JBL, among others, found reason to bypass electrolytic caps on a regular basis, in their higher-line speakers.

IIRC, Greg found that the addition of a film cap bypassing an electrolytic, could cause an increase in the Q of the crossover- which has some effect on how fast, and how far down in level, that a crossover will filter a driver... that can be a significant effect sonically.

Also remember- in the day that most of the speakers in question were made (1970s to early 1990s), the electrolytic caps were far worse in performance than what's available now. What required a bypass cap to have "adequate" performance then, may not require one noe...

Regards,
Gordon.
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Sorry, still disagreeing. Caps in the range of hundreds of uF will be used as part of a second order (or greater) low pass filter for either a LF or mid driver (moreso the LF than mid driver when in hundreds of uF). Rarely, such high value caps are used as high pass filters for blocking sub-sonic frequencies to the LF driver. For these applications, such caps will only be of concern for bass frequencies, where the value of ESL will be miniscule in comparison to the inductance of the hookup wire and any inductor in the crossover. These caps are not intended for "high" frequency applications. It bears noting that ESL is typically specified in nanoHenrys, which is insignificant considering the milliHenry values of most crossover inductors and, in particular, the tolerance of such inductors. If anyone is concerned about a capacitor's ESL, they should also be dressing the speaker's internal wiring to minimize inductance.

As for JBL and their bypass caps, many believe that was done for marketing and not for technical reasons. My JBLs (late '80s vintage 4408) with bypass caps don't have any electrolytic caps. They are all mylar caps.

Also, I thought we were talking about replacement caps, which would normally be modern caps. Any electrolytic cap I come across that is more than 20 years old is tossed in the trash.
 
I have a lot experience with old capacitors restoring vintage portable AA5 Radios. The aging problem you run into with The tube type Zenith Trans-Oceanics post WW2 is they used war surplus capacitors. They varied widely in quality. On the other hand the RCA-Victor Strato-World didn’t they used Cornell Dubilier cap’s. More often than not these 65.+ year old cap’s are OK. I still change them out as the modern replacements are a fraction of the size and rated for a far higher voltage.
 
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