The continuing saga of the charge coupled network

[Allanvh5150]

I thought that I would continue the discusion on the topic. Sorry Widget :). Everyone, or most, here know that charge coupled networks do work, the proof is in the pudding. The senior members her don't take to kindly to "JBL bagging" so please make sure that no one does. JBL spend quite a lot of cash on R&D so you can guarantee that when they introduce a new idea it will actually have merit. For all the members who are non beleivers I would recomend building a very simple CC network and do a listening test. I understand the technical aspects of the CC network and how it works in practice but there is one point that I dont understand at all. JBL compare how it works with Class A verse Class B amplifiers. For those that don't know, Class B crosses the "zero point" whereas in Class A the waveform is basically "pushed" away from the zero point by a fixed DC voltage. In this way the waveform never crosses the zero point so we get a purer sound. The bias viltage to get pure class A operation needs to be higher than the maximum peak input voltage though.
My question is this. If we apply a signal to our xover of say 40 volts, which for arguments sake is 200 watts into 8 ohms, how can a 9volt supply fully bias the main signal? Would it not need to be at least half of the peak to peak input voltage?
To my way of thinking a 9volt supply will only fully bias an 18volt peak to peak signal. Am I correct? :)

P.S. I know this is getting to be a very tired topic but I would like to know this final detail. So jump in.

[4313B]

Please keep this thread clear of all posts until December 6th.

Thanks.

[gtimbers]

I was asked to make a brief response to this last post, so here it is. The capacitor biasing is something that has existed for many years. Tube equipment does it automatically since there is usually a large DC offset between stages. Some early transistor amps/preamps had two polarized caps in series with the center point going to ground through a large resistor.

I personally became aware of this technique for speaker systems through communications with Ed Meitner, currently of EMM Labs. He is a wealth of information regarding these "tricks" to help linearize or improve the sound of passive components.

It turns out that the bias trick actually increases measured IM distortion and the higher the bias voltage, the greater the increase. It is not by a great amount, but it is measureable. The sound imporvement (or change) is very rarely perceived as worse and is never linked with a increase in IM distortion. The sonic effect is one of smoothness, increased spaciallity, detail and stuff like that. IM has a muddling or confusing effect so I doubt that this particular steady state measurement is explaining the sound difference either way.

Simply put, we are striving to create a class A situation but as was just pointed out, depending on the bias voltage with respect to the voltage across the capacitor, we may only have an "A" condition up to a particular drive level. So if it makes you happier, consider the change to be class AB, but heavily biased to A. You must also keep in mind that the voltage across the input terminals of the crossover network does not tell you what voltage or current is applied to any individual component. Some parts block signal and others shunt signal so the loading on a particular part is not obvious. For the most part, the caps are well taken care of with 9 volts, even at healthy drive levels. The obvious choice for 9 volts is the small cheap battery and holders that are available. No current is involved so a smoke detector battery and holder is a natural choice.

We did do one system with 18 v (M9500). Certain of the Japanese reviewers thought it was an improvement. I can't personally tell any difference. I am also told on a regualr basis (again by our Asian customers) that the battery must be changed at least every 90 days and that the sound degrades after that. Once again, I have not been able to "hear" any difference after 90 days and the battery is certainly still good for many years from a voltage standpoint.

What playing around I have done with initial application of a battery to a biased circuit (that has not been previously powered up) is that it takes about 3-5 seconds for the soundstage to change. I have tried to measure the voltage level in that time period and it seems that several volts is all that is necessary to accomplish 90% or more of the improvement. Once a circuit has been energized, it is nearly impossible to return it to zero. You have to individually short out each cap and leave them shorted for a while or else they will creep back up somewhat. If you replace the battery with a short and play the system for a while, the caps will start to bias themselves, although not to anywhere near the same degree.

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.

[speakerdave]

Mr. GT,

It's very nice of you to come address the peanut gallery.

Thanks,

David

[Ian Mackenzie]

2nd that ...

Greg has again offered us some great insights :).

[Allanvh5150]

Hi Greg,

Thanks for the answer to my question. I knew the theory behind it but had not read the correct answer. Everything that I read conflicted in some way. Its all very simple really. Hopefully now the debate will stop raging.
Once again, thanks for the answer. I did not think that my question would invoke a response from the man himself.

Allan.:)

[mini]

I was asked to make a brief response to this last post, ... I have never heard a capacitor type that didn't improve (or change) including the nearly perfect teflon variety.

Hi Greg,

Nice talk You gave and way comprehensive. I dropped You a PM.

Thanks!

[Doc Mark]

Hello, Greg,

Thank you, so very much, for your comments on this topic! I know it's been a hot topic here at LH, and your thoughts on all this are very much appreciated!

It's also very nice to see you so involved with those of us who have loved JBL components for so many years. At a NAMM show, many years ago, I met Mark Gander and was happy to have quite a bit of time with him, discussing a JBL project I was hoping to undertake. It was he who first suggested that I move on past the LE15 woofers, and explore the possibilities of the 2235H. Many years later, I have found his suggestion to have been absolutely dead on the money, and love the 2235H woofers!

Since I became an LH member, I've read several of your own comments on such things as 4-way systems, and have found them to be very well thought out, and with much merit. Like I did that day with Mark, I really do appreciate your taking the time to share your thoughts and experiences with "things JBL", and how to best make use of the components we all love so very much! Here's hoping you will visit us now and then, and I will always look forward to any and all information you wish to share with us. Take care, and God Bless!

Every Good Wish,
Doc

[jblsound]

Thanks Greg for that info.
Having biased a pair of custom L212s almost 5 years ago, I totally agree with your statement about sonic effect is one of smoothness, increased spaciallity, detail.

And like you say, it cost a bloody fortune. The C-C crossovers for the L212s cost me $150/ea, which consists of one card for each driver.

The cost to do a pair of my PT800s I've figured to be at least $225/ea, as the caps required are quite a bit larger than needed for the L212.

[mech986]

G.T., Thanks so much for your explanation and further details on how CC networks were used and experimented with. I had the exact same question of bias voltage and I'm happy to have heard answers and practical experience.

A colleague of yours, Tom Swem, has recently joined again to comment a bit on a prototype speaker he has. Not sure these were ever "official" L400 prototypes but interesting nonetheless. The thread is here:

http://www.audioheritage.org/vbulletin/showthread.php?t=23098

Regards,

Bart


Mini,

Some more information and enlightenment can be had from other GT posts, notably this one on his reflections and analysis of the 4345. Many of the issues you had questions about, especially directivity, crossover and network design, as well as driver integration, are touched on here:

http://audioheritage.org/vbulletin/showpost.php?p=110075&postcount=27

[scott fitlin]

Hello Mr. Timbers, and thank you for your in depth explanation of biasing caps, and theory of operation.

Based on your wisdom, and the schematic provided by a forum member, I am going to have a friend who is a wiz at this type of thing fabricate some some boards for me, and take it from there!

I'm already anxious to hear what the results will be.

Thank you, and have a GREAT holiday season, :happyh::xmas::happyh:

[jblsound]

Hello Mr. Timbers, and thank you for your in depth explanation of biasing caps, and theory of operation.

Based on your wisdom, and the schematic provided by a forum member, I am going to have a friend who is a wiz at this type of thing fabricate some some boards for me, and take it from there!

I'm already anxious to hear what the results will be.


The improvement will be superb. I would suggest using Solen polypropylene caps.

[4313B]

I have added the inital question and Greg's response to the Technical Section as would be appropriate. :)

[scott fitlin]

The improvement will be superb. I would suggest using Solen polypropelene caps.Agree, and since the Solens are the recommended cap by almost everyone, that IS what I am ordering!

I have one more question, since I use six horns and drivers powered by 1 amplifier, do I make two biased cap boards, amp feeds boards , 1 per channel? Or six individual biased cap boards, 1 per driver?

Cause I'm not really sure!

Thank you for your input, :bouncy:

[jblsound]

Agree, and since the Solens are the recommended cap by almost everyone, that IS what I am ordering!

I have one more question, since I use six horns and drivers powered by 1 amplifier, do I make two biased cap boards, amp feeds boards , 1 per channel? Or six individual biased cap boards, 1 per driver?

Cause I'm not really sure!

Thank you for your input, :bouncy:
It would depend on how much space you have. When I did my L212s, the original XO was on one 4x7 card, that fastened to the side. But I had to build a card for each driver as the caps are twice the size and twice as many. That took up a lot more room.

Plus I think its better to have one card (board) for each driver.

[SEAWOLF97]

this post was interesting, the reasoning ??? (on the highlighted part)



Before closing I should comment briefly about the 250 - 4345 comparison. Simply put, I prefer a 250. I like the bass quality of the LE14 woofer. Alway have and always will. The 2245 when used as a dedicated sub is one of the best sounding woofers ever. It has an amazing blend of speed, pitch and punch. So does the 14" but the 18" is better. Unfortunately the 18" dislike for passive networks hurts it more than the 14" is hurt by a passive network. I think the mid and high range on the 250 is smoother and much more open however the 4345 wins by a bunch in terms of effortless dynamic sound. I have made all of the above changes to 250 systems (except for separate amp on UHF) and the improvement is huge.I have not done so on the 4345 but I suspect that that system will benefit from theses changes more than a 250 would. If both systems were tweaked out to about the same level, I suspect it would be very hard to come up with a clear overall winner, but I think I might lean towards the 4345 as having the greater potential..

[scott fitlin]

They go in place of the capacitors you currently have between your amp and the compression drivers.... you are running protection capacitors on your compression drivers right?Actually, no I don't, and I have never had problems, I don't blow comp drivers, never really have, either.

But, It is relatively simple enough to do, and six small boards, with caps, and 9v battery, and holder, encased in a small, clear plastic housing that can be mounted to the cabinet under the comp driver is no problem to fabricate.

I'm asking questions, because I have never done this before, and have no experience with it, although it seems intuitively simple enough.

My friend will make them, and they will come out like a factory made product, that can be screwed down to the top of the cabinet, directly under each 2441,s terminals.

:D

[Earl K]

ThankYou 4313B for extending an invitation to Greg Timbers to talk on the subject ( of DC biasing ) .

And ThankYou to Mr. Timbers for accepting and then prompty laying out his thoughts .


<> Earl K

[4313B]

this post was interesting, the reasoning ??? (on the highlighted part)I think the combination of the aquaplased diaphragms and the biased networks work wonders on the 4344, 4345 and 4355. I've done the 250Ti, 4345 and 4355 in addition to other systems. The 4345 and 4355 are simply more dynamic. What I personally noticed on the 4345 and 4355 was the lowering of the fatigue level whereas the 250Ti just sounded better.
ThankYou 4313B for extending an invitation to Greg Timbers to talk on the subject ( of DC biasing ) .You are most welcome! :) I am sincerely in his debt. He has been a remarkable inspiration for many years. :yes:

[scott fitlin]

ThankYou 4313B for extending an invitation to Greg Timbers to talk on the subject ( of DC biasing ) .

And ThankYou to Mr. Timbers for accepting and then prompty laying out his thoughts .


<> Earl KDitto.

[SEAWOLF97]

What I personally noticed on the 4345 and 4355 was the lowering of the fatigue level whereas the 250Ti just sounded better.:yes:

not to belabor , but can you tell me what "better" means in this context ?

[scott fitlin]

More questions, :D, I got millions of them, too!

I am looking at the Solen film caps, they are available in polypropylene and aluminum foil, polypropylene and tin foil, and teflon and tin foil.

What would you use, and what voltage rating? I power six 2441J on a Crown DC-300A.

http://www.partsconnexion.com/catalog/CapacitorsFilm.html

[Rolf]

What the h.... are we thinking? The man himself, responsible for a lot has spoken. He knows much more than the most of us do.

Thanks Greg for your time to enlighten us once more.

[4313B]

not to belabor , but can you tell me what "better" means in this context ?Significantly clearer and more three dimensional. Greg's description was "staggering" when we talked about biasing the 250Ti years ago. I'd agree. You might want to PM jblnut about his pair of biased 250Ti's.

[hjames]

Significantly clearer and more three dimensional. Greg's description was "staggering" when we talked about biasing the 250Ti years ago. I'd agree. The older systems just seem to benefit even more and Greg's 4345 and 4355 designs respond particularly well.

So, I could assume that even an ancient system like my 4341s would improve quite a bit with an upgrade to CC networks ... even without the 2245s ...

[4313B]

I thought you basically had 4344 components now Heather...

2235H, 2122H, 2425J, 2405

[hjames]

I thought you basically had 4344 components now Heather...

2235H, 2122H, 2425J, 2405

well, soon ... :D

still using (most of) the original crossovers and those itty bitty boxes tho ...

[alskinner]

I check this forum everyday in hopes of hearing something from "The Man".

A novice at best, I have the utmost respect and admiration of what it takes to bring a system from scratch to a world class product.

Had it not been for you and some of the heavyweights on this forum, I would not have delved into a hobby that I love.

Thanks and Regards
AL

[4313B]

I am looking at the Solen film caps, they are available in polypropylene and aluminum foil, polypropylene and tin foil, and teflon and tin foil.

What would you use, and what voltage rating? I power six 2441J on a Crown DC-300A.What is the frequency of the active filter crossover going to the 2441's? These are what you could use:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-608

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-612

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-616

[scott fitlin]

My horns run 750hz - 7k, 12db butterworth.

OK, thanks, I am looking at your suggestions right now.

:bouncy:

[scott fitlin]

What about bypassing the bigger cap, with a smaller cap of the teflon type? Is it neccesary? Would there be any benefit? ? Would it be an insignicant improvement? Or would it not be good to do?

Please advise!

Oh dang, it looks as though I asked MORE than 1 question! :banghead:

:D

[mech986]

What about bypassing the bigger cap, with a smaller cap of the teflon type? Is it neccesary? Would there be any benefit? ? Would it be an insignicant improvement? Or would it not be good to do?

Please advise!

Oh dang, it looks as though I asked MORE than 1 question! :banghead:

:D

Hi Scott,

Don't know about the teflon part, but some of JBL Flagship speakers with CC crossovers have some bypassed, others, not. There is usage of bypass caps in both high and low sections so it may depend on specific application or results of listening tests.

See these:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/K2S9800-9800SE%20ts.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/K2S5800%20ts.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/Everest%20DD66000%20ts.pdf

If its good enough for these, I think I'd try it.

Regards,

Bart

[pos]

I think the S9800SE uses biased Solen caps without bypass, whereas the original S9800 used cheaper biased caps with bypass.

[scott fitlin]

I'm definitely using Solen caps, Greg Timbers likes it, 4313B likes it, pretty much everyone says this is the way to go, so, this is the way Im going to go.

Im investigating all possibilities.

[jblsound]

What about bypassing the bigger cap, with a smaller cap of the teflon type? Is it neccesary? Would there be any benefit? ? Would it be an insignicant improvement? Or would it not be good to do?

Please advise!

Oh dang, it looks as though I asked MORE than 1 question! :banghead:

:D

If you use all polypropylene caps in a C-C XO, bypass caps aren't needed, as the C-C caps will do the job.

[Allanvh5150]

Hi all,

The addition of bypass caps to any crossover is a good idea, especially with charge coupled designs. The larger the capacitor value, the higher inductance figure that it has. Putting a small value bypass capacitor in parallel with all the larger capacitors will nearly cancel the inductance of them. :)

[scott fitlin]

If you use all polypropylene caps in a C-C XO, bypass caps aren't needed, as the C-C caps will do the job.Yes, I see what your saying, BUT, the larger 82 to 100uf Solens are metalised polypropylene, and the smaller values are available as polypropylene film/tin foil, or aluminum foil, or teflon film, and tin or aluminum foil.

I ask questions, because I see there are differences, and the bigger caps are only available as metalised film.

BTW, this isnt a XO in my system, I am actively XO, but, these are additional inline caps that will be CC for the sonic advantages.

But, I think I'm just gonna go with the recommended caps, IF Greg Timbers likes it, I should like it, too!

And, I was also looking at the Mundorf caps, BOY those little critter caps get PRICEY!

To be very honest, though, I am fully aware of just HOW different various caps, same value but different materials can sound. So, I am garnering all the information I can get, DO IT RIGHT THE 1ST TIME, AND ONLY DO IT ONCE!

As I said, GT, 4313B, Allan, jblsound, and everyone else says this is good, so, Im jumping on the same bandwagon.

Solen it is!

My new Marchand XO,vers will have Burson Discreet Op amps, and Discreet Voltage regulators, Takman resistors, a couple of Riken ohm Carbon compostion resistors in key points for that certain flavor they have, and I have to select lytic and film caps for this project, remains undecided at this point.

Im taking my room to another level, :bouncy:

[jblsound]

Hi all,

The addition of bypass caps to any crossover is a good idea, especially with charge coupled designs. The larger the capacitor value, the higher inductance figure that it has. Putting a small value bypass capacitor in parallel with all the larger capacitors will nearly cancel the inductance of them. :)
AS I understand it, polypropylene by-pass caps are for making a normal XO more dynamic. In a C-C network, that has all Polypropylene caps, using by-pass caps is not required.
And I seem to remember GT saying that in a previous post.

[Allanvh5150]

AS I understand it, polypropylene by-pass caps are for making a normal XO more dynamic. In a C-C network, that has all Polypropylene caps, using by-pass caps is not required.
And I seem to remember GT saying that in a previous post.

Taking it from a purely electronic point of view, bypassing makes sense. Unless you know a reason why not?:)

[Earl K]

What about bypassing the bigger cap, with a smaller cap of the teflon type? Is it neccesary? Would there be any benefit? ? Would it be an insignicant improvement? Or would it not be good to do?

- Broadly speaking, it has been my experience that bypass caps simply don't work within dc biased networks .
- They won't give you the expected results .

<> cheers

[scott fitlin]

- Broadly speaking, it has been my experience that bypass caps simply don't work within dc biased networks .
- They won't give you the expected results .

<> cheersThanks Earl. I'm going to keep it simple, order the 100uf 400v Solen polyprops, from PE as 4313B suggested in an earlier post. IF it works for you guys, it works for me, too!

On a side note, I happened to glance thru the Duelund capacitors listed at Parts Connexion, H__Y S__T, up to $3500 each for a single film cap!!!!!

Who buys this stuff?

Seriously, we are ALL in the wrong business. Lets make capacitors.

:dont-know

[jblsound]

Thanks Earl. I'm going to keep it simple, order the 100uf 400v Solen polyprops, from PE as 4313B suggested in an earlier post. IF it works for you guys, it works for me, too!

On a side note, I happened to glance thru the Duelund capacitors listed at Parts Connexion, H__Y S__T, up to $3500 each for a single film cap!!!!!

Who buys this stuff?

Seriously, we are ALL in the wrong business. Lets make capacitors.

:dont-know
I'm sure some audiophiles might think they're worth it. But those guys also think $500 AC power cords, $10/ft speaker wire is worth it.

[4313B]

I'm sure some audiophiles might think they're worth it. But those guys also think $500 AC power cords, $10/ft speaker wire is worth it.And all the while they're still stuck with listening to recorded media. :rotfl:

[jblsound]

- Broadly speaking, it has been my experience that bypass caps simply don't work within dc biased networks .
- They won't give you the expected results .

<> cheers
That's exactly the point I was making to Allanvh5150. Just the fact that all the caps in the circuit are polypropylene would serve no benefit to add by-pass caps.

[scott fitlin]

And all the while they're still stuck with listening to recorded media. :rotfl:Yes, BUT, The power cords for $500ea are like having the performers come to your living room, they say!

And a $500 power cord, AND some extasy pills, I wouldn't be surprised if one actually thought they did!

:D

[Ian Mackenzie]

And all the while they're still stuck with listening to recorded media. :rotfl:

http://www.duelundaudio.com/About_Steen_Duelund.asp

Fondly known as the mad loudspeaker professor, Steen Aa Dueland's influence on the the Gryphon Cantata, Poseidon and Trident resulted in many ideas such as biasing crossover capacitors and Linqwitz Grainer Q circuit. In his diy articles Dueland refers to biasing capacitors.

http://www.gryphon-audio.dk/default.asp

http://www.gryphon-audio.dk/default2.asp

The electrolytic capacitors in the impedance correction circuit are pre-biased to maintain a constant charge in order to eliminate crossover distortion at zero electric potential, resulting in audibly enhanced stability and substantial gains in body, timbral color and image coherence. Operating the battery-biased crossover in “Class A” mode ensures a smoother, more richly detailed three-dimensional presentation.

The Trident crossover network, based on wax-impregnated air-core inductors wound from copper foil and stacked foil capacitors potted in epoxy to resist mechanical interference, ensures undetectable, smooth transitions across the audible range.

28 V DC bias is applied to the capacitors, eliminating crossover distortion at zero electric potential for audibly enhanced stability and substantial gains in body, timbral color and image coherence.

[4313B]

Nice links Ian, what a world that looks like to live in!

[4313B]

Biasing protection caps is just a suggestion. If you don't use protection caps on your compression drivers, for whatever reason, then you don't have anything to bias.

[Earl K]

Scott,

- While you're at it ( dc-biasing your horn circuit ) give a thought to dc-biasing the front end of your horn amps , assuming they have balanced inputs . The pittance invested in the necessary small value caps makes this a no-brainer .

- I did this with my Bryston 2BLP ( pros ) and the result was quite spectacular ( this was done @ 4 years ago ). It makes sense to combine this with any dc-biasing that is implemented after the amp. In my view, it imposes on the whole circuit a sort of "feed-forward" super-symmetry ( a la Nelson Pass ).
- As mentioned, the sonic results are way beyond what one expects .


- The 2BLP has no dc blocking caps in the front end / so adding a pair a battery-biased caps in front of the servo-balanced inputs was quite simplistic . I used .048 mfd ( I think ), 2% polystyrene caps . I didn't use any load resistors in this circuit .

- What amps are you using ?
- Any idea on their stated input impedance ( look for balanced & unbalanced specs. )
- I'd recommend a filter that has a turn-over frequency between 100 to 200 hz ( given your 750 hz crossover point ) .
- If interested, I'll run you through the design process .

<> cheers

[scott fitlin]

Hi Earl, sounds interesting, and I have NO experience with these types of mods, and enhancements, so, I am ALL ears, open to learning.

I went back to Crown, DC-300A on my six JBL 2395/2441 horns, D-150A on six 2404, and D-150A on 16 2402,s!

I used PSA-2,s on the TAD 1603,s, but, this year, am upgrading to Crowns newer amplification, on 18,s used a combination of Macro Tech 3600,s, an I Tech, and QSC 6.0II, again, this year, Macro Tech i series replaces older amps, New Music & computers + New amps and modern drivers = HAPPY SCOTTY! :bouncy:

I must say this, though, IT has been a learning experience, and now that the new music, and download revolution is here to stay, there really IS somethin to be gotten out of it, BUT, I had to be open minded to it, and willing to work at it, and accept that I must do some things a bit differently than we did years ago when setting up and voicing for vinyl playback!

However, once I did, there AIN'T no going back!

First thing I am going to do, regarding inline caps, is take a pair of 400v caps, put em on a pair of 2441,s, and LISTEN to what happens. This is not biased cap networks or such, just a starting point to see what happens, etc!

Of course, I have amps with balanced inputs, etc, and I would love to hear your suggestions.

:D

[Earl K]

First thing I am going to do, regarding inline caps, is take a pair of 400v caps, put em on a pair of 2441,s, and LISTEN to what happens. This is not biased cap networks or such, just a starting point to see what happens, etc!

- Okay, that makes sense to me ( take one step at a time )

- Reactiavte this thread after you've dc-biased ( the after amp ) circuit and then listened for some time ( that implies January ).

<> cheers

[scott fitlin]

- Okay, that makes sense to me ( take one step at a time )

- Reactiavte this thread after you've dc-biased ( the after amp ) circuit and then listened for some time ( that implies January ).

<> cheersAgree!

:bouncy: