"Charged Coupled" crossovers?

[jblsound]

You can take this opinion for what it has cost you. I have been very pleased with biasing for many years. I use it in all applications that involve a capacitor and I have rarely been disappointed. Results may vary so if it doesn't do it for you that is okay too. It cost a bloody fortune to implement as it requires 4 times the capacitance and double the capacitor parts count. The network size gets huge as well. Inspite of this, I have never heard a capacitor type that didn't improve (or change) including the nearly perfect teflon variety

Above is the last paragraph from that link. And I've mentioned to others you just don't C-C just any ole speaker. B/C of the cost of the C-C circuit the speaker system in question needs to be of a high quality to start with.

The cost to C-C a pair of L212s was about $300. So one certainly wouldn't spend that kind of money on speakers that only cost $300/pr new.
With the current JBL Consumer series I wouldn't spend the time, much less the money, to C-C any series below the Performance Series.

Now for bypass, its quite different, its a small cost. But, if one is thinking of bypassing an old system of say 30 years, give or take, if the XO in question is original, it would be best to build new XOs and bypass them, imo, instead of just adding bypass to old worn out XOs.

[midlife]

I like it, where do I get mine?

[pierce]

I like it, where do I get mine?

(eg, you buy the parts, you build your own)

[Robh3606]

Rob, I am fascinated by your argumentative stance in this thread. I would really like to understand your thoughts on the subject. Do you think that biasing capacitors is without merit? If so are your objections based on theoretical grounds, or have you experimented and failed to hear an improvement?

Hello Steve

I don’t have an issue with CC networks. I have been using them exclusively on any projects I have built since 2003. As a matter of fact if you look at the first post in this thread the linked thread is the original CC thread I started back in 2003. I was an early adopter and have never looked back. I agree with you and think they really do make a difference that is worth any added part costs. So I am one of you guys in that respect.

The reason we do this is to keep the capacitors dielectric from crossing 0 volts on each cycle of the AC waveform. The DC bias prevents this because the capacitor is charged to 9 volts and will remain that way as long as the battery is in the circuit.

My bone of contention is the perceived loss of bias when the sine wave peaks go beyond -9 volts. If you use superposition you would just add and subtract the voltages. But that doesn’t really work here because it ignores the time domain and does not address what is happening inside the capacitor. If you had a 12V PP signal on the negative side you would have the voltage across the capacitor cross 0 volts at -9V and peak at -3 volts at the -12 peak.

The voltage across the capacitor does indeed cross through zero and go negative. That said the dielectric has not crossed through 0 volts because it has not had enough time to discharge. You would have to discharge the 9 volt charge for the capacitors dielectric to cross back through 0 volts. So even though the capacitors see’s a negative voltage the capacitor remains biased due to the long charged and discharge rates of the capacitor resistor combination and the battery.

The capacitors charge and discharge rate is not linear. It’s an exponential curve so it is a complex function of time, not just a static DC voltage. If you compare the discharge curve to the duration of any program material peaks, in the time domain, it is clear that the short peaks beyond 0 volts have little effect on the biasing considering the battery is there to maintain the +9v charge on the capacitor.

So there you have it. I just don’t see where the capacitors dielectric ever crosses back over the 0 volt reference after the DC bias is applied.

My eyelids are getting heavy now

Rob

[spkrman57]

It's exactly like adding kiwi to a strawberry drink. The drawback is, if you don't like kiwi or strawberry you're screwed.

I've been adding kiwi to my grapefruit juice!!!

Ron......

[pierce]

I'm inclined to suspect that another reason why 9V is enough regardless of the signal negative peak voltage is that a few millivolts of glitch on a large signal is insignificant, while that same few millivolts of glitch on a small signal would be obvious.

[Robh3606]

while that same few millivolts of glitch on a small signal would be obvious.

Good point and that's where you hear it as well on the low level stuff. Same with the aguaplas, helps resolve the lower level details. They make a great combination.

Rob

[Hoerninger]

If you use superposition you would just add and subtract the voltages. But that doesn’t really work here because it ignores the time domain and does not address what is happening inside the capacitor. ...

As I had thrown in the idea of Superposition I want to reply to your post.

Superposition is an often used approach in physics when a problem can't be solved directly. In electrical engineering it is inevitable for calculating electrical networks. This holds not only for DC but for sinusoidal AC and all other forms of current changes.
When using for example Leap or Spice (LTSpice) for calculating this is done automatically for the user.

When the capacitors are charged by the 9 V batterie it can be switched off afterwards as long as there is no loss due to leakage. When an AC current is applied the initial charging changes. The time constant for the former charging is irrelevant as the AC current flows through the capacitors and the speakers with about 8 Ohm and not through the ca 2.2MOhm resistor and the 9 V batterie (now regarded as short circuit). The speaker has a much lower resistant and thus the time constant is much lower. Now the frequency dependend effect comes into account.

But just like you I discuss here only the variations in time and not the frequency dependency. So I am with you in the time domain but not in the frequency domain. (The corresponding mathematical descriptions can be transformed vice versa.)

It can be said that the dielectric has a voltage. But in the context here it is not helpful as the difference in charge concentration between the two sides of the electric (equivalent to voltage) is caused by the charges on the plates. The dielectric will be polarized. When there is no charge on the plates of the capacitor than there is no polarisation in the dielectric.
(Just ignoring capacitor soakage for the moment.)
____________
Peter

[Ian Mackenzie]

Hello Steve

I don’t have an issue with CC networks. I have been using them exclusively on any projects I have built since 2003. As a matter of fact if you look at the first post in this thread the linked thread is the original CC thread I started back in 2003. I was an early adopter and have never looked back. I agree with you and think they really do make a difference that is worth any added part costs. So I am one of you guys in that respect.

The reason we do this is to keep the capacitors dielectric from crossing 0 volts on each cycle of the AC waveform. The DC bias prevents this because the capacitor is charged to 9 volts and will remain that way as long as the battery is in the circuit.

My bone of contention is the perceived loss of bias when the sine wave peaks go beyond -9 volts. If you use superposition you would just add and subtract the voltages. But that doesn’t really work here because it ignores the time domain and does not address what is happening inside the capacitor. If you had a 12V PP signal on the negative side you would have the voltage across the capacitor cross 0 volts at -9V and peak at -3 volts at the -12 peak.

The voltage across the capacitor does indeed cross through zero and go negative. That said the dielectric has not crossed through 0 volts because it has not had enough time to discharge. You would have to discharge the 9 volt charge for the capacitors dielectric to cross back through 0 volts. So even though the capacitors see’s a negative voltage the capacitor remains biased due to the long charged and discharge rates of the capacitor resistor combination and the battery.

A zero or 0 Dc voltage condition on a capacitor can only exist where there is a zero Dc potential present as in a normal series "single" capacitor without a Dc voltage present.

The capacitors charge and discharge rate is not linear. It’s an exponential curve so it is a complex function of time, not just a static DC voltage. If you compare the discharge curve to the duration of any program material peaks, in the time domain, it is clear that the short peaks beyond 0 volts have little effect on the biasing considering the battery is there to maintain the +9v charge on the capacitor.

So there you have it. I just don’t see where the capacitors dielectric ever crosses back over the 0 volt reference after the DC bias is applied.

My eyelids are getting heavy now

Rob

Great post Rob.

My take is that 9 volts is arbritrary and can be any voltage up to the DC working voltage of the capacitor

As such the ac voltage has a linear +-4.5 peak-peak swing within the 0-9 volt dc range of the battery. This is much like the Dc bias current of a SE class A amp but we are talking voltage here not Dc current.

The point being to move or shift the anode/cathode 0 volt crossing up so the ions are no longer moving in the "zero volt" non linear region. ie a non polarised "ideal" capacitor..

This principle is used in so called biasing of many device such as BJT, mosfets and Jfets where we pick a region on the voltage/current gain curve where the device is most linear and apply a constant current (bias) or constant voltage (cascoding) to ensure the non linear distortion caused by the device is minimised.

In practise for domestic applications 0-9 volts allows a large majority of hi resolution (low voltage) audio signal to pass within the linear range and beyond that at the larger superimposed a/c voltage swings that are typcially bass transients are less critical.

A/c voltages across the whole audio band sums for a total peak A/C voltage. In this respect the peak voltages sum additively to increase the magnitude of the peak to peak A/C voltage. They are only superimposed on any the DC voltage present that actually shadows the peak ac voltage but this is not additive. ie ac and dc voltage to not sum together as such nor do ac and dc currents.

In respect to the maximum linear voltage swing as Greg comments elsewhere they tried +18 volts and some Japanese audiophiles feedback was its was an improvement but this is perhaps difficult to validate.

As to what happens and why plug your crossover capacitors into an A/c circuiy and apply a sine wave and listen to the capacitors sing. The singing is the plates rattling around. Because the plate move this causes non linear behaviour and is often termed noise and is in essence distortion. The charge-coupling helps control this issue but it does not control inductance due to the wrapping of the plates much like a coil of foil.

[jblsound]

As to what happens and why plug your crossover capacitors into an A/c circuiy and apply a sine wave and listen to the capacitors sing. The singing is the plates rattling around. Because the plate move this causes non linear behaviour and is often termed noise and is in essence distortion. The charge-coupling helps control this issue but it does not control inductance due to the wrapping of the plates much like a coil of foil.

I seem to remember reading, from a few years back, and I think it was Greg's statement, that applying DC v to a cap tightens up loose caps, which you're referring to. As such removes that distortion.

[Ian Mackenzie]

See this interview:

http://www.sonicstate.com/news/2008/...-sound-better/

This take nothing away from Charge-Coupling and I see it as an alternative means of improving capacitor performance.

Of course direct amplifier connection (pure-active) eliminates all these issues.

But Charge-Coupling cleans up a lot of the most audible undesirable characteristics without resorting to over the top (expensive) capacitors.

Ian

link fixed

[Hoerninger]

ICW (UK) have proved conclusively that internal vibrations inside a capacitor effect sound quality.

Concerning this point there is a AES-paper by
Menno van der Veen & Hans van Maanen
"Non-linear distortions in capacitors"
http://www.mennovanderveen.nl/nl/publicaties.html

But from the logical point of view it is not finally determined whether vibrations are fixed by CC.

But then it might be possible that CC affects Dielectric Absorbtion (DA)
http://audioheritage.org/vbulletin/s...336#post252336

Just some food for thought.
____________
Peter

[Zilch]

The source impedance for the DC bias voltage is very high, several megohms.

That of the signal is orders of magnitude lower. Since the R in R*C is low, the time constant of the AC signal operating on the capacitor is correspondingly shorter; it swamps the DC.

Put a low-impedance, higher voltage source on the capacitor, and it will charge and discharge lickety-split to and from that higher peak relative to the time constant of the battery and multi-megohm resistor. Put a 1-Ohm resistor in, instead 2.2 Meg, and the signal's going nowhere; it's the impedance differential that allows the circuit to pass the AC.

[Ducatista47]

Smart fellow. From Download 4 of Peter's link:

7. CONCLUSIONS
We have discovered a major cause of nonlinear
distortion in capacitors and we have shown
that this effect can create significant –and thus
audible- distortions in sound signals. Especially in
passive cross-over filters this effect can introduce
high levels of intermodulation distortion and thus
lead to audible differences between capacitors.
The underlying causes of these distortions
have now been unveiled and therefore, an
objective way to determine the audible quality of
capacitors can be developed. This is a major step
forward, compared to endless listening tests with
often incomprehensible results. Also, the design of
electronics can be optimised with the non-linear
properties of capacitors as parameter.

We can only hope.

I have not been a fan of meter men because they ignore hearing when ears present evidence to the contrary. If they develop their art sufficiently to measure what we actually hear, I might change my opinion. (And if they also come on board with things like phase shift affecting the listening experience to the degree that it actually does.)

Clark

[Ducatista47]

See this interview:

http://www.sonicstate.com/news/2008/...-sound-better/

This take nothing away from Charge-Coupling and I see it as an alternative means of improving capacitor performance.

Of course direct amplifier connection (pure-active) eliminates all these issues.

But Charge-Coupling cleans up a lot of the most audible undesirable characteristics without resorting to over the top (expensive) capacitors.

Ian

link fixed

I find it especially interesting that it seems to be JBL he is talking about working with on this issue. (All the hints point to them. A very large speaker manufacturer using very efficient drivers and having been trying to deal with this problem for some time.) Doesn't JBL use Solens in its high end crossovers? Perhaps they will switch to Clarity Caps now. Caps designed and manufactured to eliminate this at the source are preferable to any conceivable remedial fix.

Talk about proof of the phenomenon being audible. They designed a test capacitor so afflicted in this respect that it turned into a speaker. I agree that charge coupling, designed to address an entirely different problem, would do nothing for this one. One thing that will never change, the best crossover would be no crossover. Things in the signal path can degrade the signal, but never improve it. Neutral would be great, but rarely even possible.

It is amazing that some of these fundamental suppositions had never been investigated for veracity. The example cited of it being voltage rather than current that causes the problem by a ratio of one million to one is downright embarrassing. And the sound/vibration induced distortion in caps proved to be a groundless myth. In other words, it ends up that caps are not microphonic in the least. Since it is the Clarity Cap people that did the research I am glad I am already on their bandwagon, as I would surely have switched after seeing this.

My thanks to Ian for telling me about Clarity Caps in the first place and for pointing to this interview.

Clark