Getting crazy here
JBL call it "Charge-Coupled Linear Definition Dividing Network"
I kind of know how ccd works but I can't apply it to passive crossovers.
Anyone tried to DC bias a passive crossover?
I thought is that it could be like a class A crossover, because the components wount have to "switch" between off and on.
Maybe it would be possible to save alot of money on high-end filter caps with using ceaper ones always charged?
Maybe it is crazy, but if it is, why would one of the oldest manufactors like JBL use it on their "high-end" speaker.
I guess I have to start frying drivers with DC brute force here, if I can't get any advice on the way.
Magnus
JBL call it "Charge-Coupled Linear Definition Dividing Network"
I kind of know how ccd works but I can't apply it to passive crossovers.
Anyone tried to DC bias a passive crossover?
I thought is that it could be like a class A crossover, because the components wount have to "switch" between off and on.
Maybe it would be possible to save alot of money on high-end filter caps with using ceaper ones always charged?
Maybe it is crazy, but if it is, why would one of the oldest manufactors like JBL use it on their "high-end" speaker.
I guess I have to start frying drivers with DC brute force here, if I can't get any advice on the way.
Magnus
DC-bias
Hi Magnus,
DC biasing a passive Xover is not that new.
It´s just getting expensive:
Take a cap say 10µF. If you want it biased you need 2
caps in series each has 20µF and apply some DC voltage
over a resistor (eg 1k) to the junction.
The bias voltage should be at least as high as the maximum
peak output of your amp.(better add some volts).
Those exotic Paperinoil or tinfoil caps are marked for
polarity -> very useful.
Uli
PS: and it works indeed!
Hi Magnus,
DC biasing a passive Xover is not that new.
It´s just getting expensive:
Take a cap say 10µF. If you want it biased you need 2
caps in series each has 20µF and apply some DC voltage
over a resistor (eg 1k) to the junction.
The bias voltage should be at least as high as the maximum
peak output of your amp.(better add some volts).
Those exotic Paperinoil or tinfoil caps are marked for
polarity -> very useful.
Uli
PS: and it works indeed!
Thanks
It almost drove me crazy, I hate to have something like this bugging me.
Well I know it's not that new, but it had to be an improvment because they use it in the K2's that I think is the best sounding out there right now.
Thanks again, time for me to test, messurment, listen and see/hear for myself.
Strange if it works, why don't everyone with passive filters do it, the cost isn't that much more.
Have you played around with it alot, does the bias voltage effetct the sound.
Would a get some new problems with phase and so on?
Magnus
PS: a great SACD is Jorma Kaukonen "Blue country heart"
It almost drove me crazy, I hate to have something like this bugging me.
Well I know it's not that new, but it had to be an improvment because they use it in the K2's that I think is the best sounding out there right now.
Thanks again, time for me to test, messurment, listen and see/hear for myself.
Strange if it works, why don't everyone with passive filters do it, the cost isn't that much more.
Have you played around with it alot, does the bias voltage effetct the sound.
Would a get some new problems with phase and so on?
Magnus
PS: a great SACD is Jorma Kaukonen "Blue country heart"
Magnus,
Yes I tried, but the advantages are hardly hearable.
It makes sense in systems where everything else is
state of the art. Every cap has different behaviour
when polarized in one or the other way. This leads
to some added distortion. Now if you bias any cap
it doesn´t change polarity any more (kind of similarity
to Class A if you want).In woofer Xovers it makes no
sense as there you can hardly hear it. I use it for
my Focal tweeters and I think they sound cleaner but
thats subjective. I bias the caps with 25Volts DC.
IMHO it makes no sense to use a 9V battery. The so
achieved headroom is too lo. 9V / 8R = 5Watts!
If you drive that system higher you leave the bias
area!
Uli
PS: no it doesn´t affect phase.
2 20µF caps tin foil and a psu cost far more than one
10µF cap and this multiplied by 2 and the count of caps!
Yes I tried, but the advantages are hardly hearable.
It makes sense in systems where everything else is
state of the art. Every cap has different behaviour
when polarized in one or the other way. This leads
to some added distortion. Now if you bias any cap
it doesn´t change polarity any more (kind of similarity
to Class A if you want).In woofer Xovers it makes no
sense as there you can hardly hear it. I use it for
my Focal tweeters and I think they sound cleaner but
thats subjective. I bias the caps with 25Volts DC.
IMHO it makes no sense to use a 9V battery. The so
achieved headroom is too lo. 9V / 8R = 5Watts!
If you drive that system higher you leave the bias
area!
Uli
PS: no it doesn´t affect phase.
2 20µF caps tin foil and a psu cost far more than one
10µF cap and this multiplied by 2 and the count of caps!
Thanks
OK, great and sometimes a theoretical improvment make me think it sounds better maybee enough. Well I'm not into magics and don't expect wonders, more querious to see if it work and how much improvment it is possible to get tweaking it back and forth.
Well strange that 9V wouldn't do it, is it just a decoration in the hughs K2's?
Well I havn't start to play with it yet but have plans for it tonight tho.
Well it do cost some extra, but not as much as hearing my wife complaining over active x-overs and extra amps in the livingroom. That makes me give her my visa so she could go shopping, getting happy again.
Dentist time
Magnus
OK, great and sometimes a theoretical improvment make me think it sounds better maybee enough. Well I'm not into magics and don't expect wonders, more querious to see if it work and how much improvment it is possible to get tweaking it back and forth.
Well strange that 9V wouldn't do it, is it just a decoration in the hughs K2's?
Well I havn't start to play with it yet but have plans for it tonight tho.
Well it do cost some extra, but not as much as hearing my wife complaining over active x-overs and extra amps in the livingroom. That makes me give her my visa so she could go shopping, getting happy again.
Dentist time
Magnus
Hi Magnus,
The point is that in a commercial device like those JBLs
its necessary to build it "foolproof". Hence the 9v battery.
Better but more complicated is to use accus (2x12v for example).
Maybe the reason is that when this method is only used for caps
in the path (hipass) of tweeters or mids there will hardly be a
situation where you need more than those 5 Watts (RMS!) in
a tweeter. Normally the powerdispersion is like 100 Watts for
Bass equals about 3-5 Watts for the tweeter.
You can calculate this by analysing a signal with a FF Analyser.
Uli
The point is that in a commercial device like those JBLs
its necessary to build it "foolproof". Hence the 9v battery.
Better but more complicated is to use accus (2x12v for example).
Maybe the reason is that when this method is only used for caps
in the path (hipass) of tweeters or mids there will hardly be a
situation where you need more than those 5 Watts (RMS!) in
a tweeter. Normally the powerdispersion is like 100 Watts for
Bass equals about 3-5 Watts for the tweeter.
You can calculate this by analysing a signal with a FF Analyser.
Uli
OK
Well I know, messured that my tweeter powerdispersion at normal use is just about 0,3W, mid around 3W and bass around 9W. Maybee it's me that is to careful with the volume..
My thinking were as long as the caps are bias a little they will be "on" and at hire volumes I won't even be able to hear a differns if they are under biased?
Just tried it on my monitors with 20V and right away I couldn't hear any differense at al, but no serious listening yet.
Will listen more serious tonight, and test it in some other filters and speaker, and have my wifes super ears listen to it, then I will know.
Thanks again for taking your time.
Magnus
Well I know, messured that my tweeter powerdispersion at normal use is just about 0,3W, mid around 3W and bass around 9W. Maybee it's me that is to careful with the volume..
My thinking were as long as the caps are bias a little they will be "on" and at hire volumes I won't even be able to hear a differns if they are under biased?
Just tried it on my monitors with 20V and right away I couldn't hear any differense at al, but no serious listening yet.
Will listen more serious tonight, and test it in some other filters and speaker, and have my wifes super ears listen to it, then I will know.
Thanks again for taking your time.
Magnus
It works great
It works, even I hear the difference.
My tweeters is accuton c-12 when I first tested it in 2st order filter both unbiased and biased with audiocap theta film caps, i didn't hear any difference at al, my wife said it was a little clearer. Maybe just a subjective difference. After that I tested it in a 1st order filter with audiocaps both ways, now we both heard a difference it got clearer and the sound stage got bigger but still no big difference, don't think it was worth the effort. At last same filter tested with ICW Clarity caps, big difference between the bias and unbiased caps, the unbias ones sounded flat muffled compaired with with the bias version. The testing was far away from blind testing, so I really don't know if it is worth it yet, sometimes my brain fouls me because I want to belive in something.
I will play around with it a while and have my wife blind test it.
If a really find a big difference, I might try to pre-bias some caps in the signal path in my amp, qurious
Magnus
It works, even I hear the difference.
My tweeters is accuton c-12 when I first tested it in 2st order filter both unbiased and biased with audiocap theta film caps, i didn't hear any difference at al, my wife said it was a little clearer. Maybe just a subjective difference. After that I tested it in a 1st order filter with audiocaps both ways, now we both heard a difference it got clearer and the sound stage got bigger but still no big difference, don't think it was worth the effort. At last same filter tested with ICW Clarity caps, big difference between the bias and unbiased caps, the unbias ones sounded flat muffled compaired with with the bias version. The testing was far away from blind testing, so I really don't know if it is worth it yet, sometimes my brain fouls me because I want to belive in something.
I will play around with it a while and have my wife blind test it.
If a really find a big difference, I might try to pre-bias some caps in the signal path in my amp, qurious
Magnus
It works, even I hear the difference.
My tweeters is accuton c-12 when I first tested it in 2st order filter both unbiased and biased with audiocap theta film caps, i didn't hear any difference at al, my wife said it was a little clearer. Maybe just a subjective difference. After that I tested it in a 1st order filter with audiocaps both ways, now we both heard a difference it got clearer and the sound stage got bigger but still no big difference, don't think it was worth the effort. At last same filter tested with ICW Clarity caps, big difference between the bias and unbiased caps, the unbias ones sounded flat muffled compaired with with the bias version. The testing was far away from blind testing, so I really don't know if it is worth it yet, sometimes my brain fouls me because I want to belive in something.
I will play around with it a while and have my wife blind test it.
If a really find a big difference, I might try to pre-bias some caps in the signal path in my amp, qurious
Magnus
I think a double blind test may reduce the difference even further. But it's such a cool idea, just having it in circuit and believing it works may make it well worth the cost.
9v DC Bias - Charged Coupling
From what I remember (good or bad) - Joe Rasmussen threads - that it's best performance (9v) was the start like when you have silence/low output to transitions, full gain if I can say that, I'm not an engineer.
http://www.diyaudio.com/forums/multi-way/97043-elsinore-project-thread-23.html#post1793450
http://www.diyaudio.com/forums/multi-way/141929-dc-bias-crossovers-mostly-tweeters.html
From what I remember (good or bad
) - Joe Rasmussen threads - that it's best performance (9v) was the start like when you have silence/low output to transitions, full gain if I can say that, I'm not an engineer. http://www.diyaudio.com/forums/multi-way/97043-elsinore-project-thread-23.html#post1793450
http://www.diyaudio.com/forums/multi-way/141929-dc-bias-crossovers-mostly-tweeters.html
I've seen this in old (1950s) magazine articles where they were using polarized power supply caps and applied the bias so that the caps had enough bias to be properly polarized. A polarized electrolytic with reverse bias will have high leakage and could lead to overheating.
As to doing the same with modern non-polar caps, I would love to see some distortion measurements. I'm sceptical.
And if the signal is higher than 9 volts?
David S.
As to doing the same with modern non-polar caps, I would love to see some distortion measurements. I'm sceptical.
And if the signal is higher than 9 volts?
David S.
Dave
The way I see this is to allow the use of an electrolytic instead of a nonpolarized type - much lower cost. We all know that electrolytics are a bad idea, even the nonpolarized ones can be a problem because these types of caps need a polarizing voltage to work right. The 9v does that.
Sounds good (marketing wise, I doubt that there is much audible difference), saves money, what's not to like?
Like you I am extremely dubious about this doing anything with a non-electrolytic cap.
The way I see this is to allow the use of an electrolytic instead of a nonpolarized type - much lower cost. We all know that electrolytics are a bad idea, even the nonpolarized ones can be a problem because these types of caps need a polarizing voltage to work right. The 9v does that.
Sounds good (marketing wise, I doubt that there is much audible difference), saves money, what's not to like?
Like you I am extremely dubious about this doing anything with a non-electrolytic cap.
When I was a kid would wire two sets of polarized lytics cathode to cathode and run 24v DC across them. Something my dad suggested for all I remember.
Back then if I wanted parts you either saved forever or went dumpster diving. I still have a mess of gold plated computer IC's from the mid '70's from those expeditions and which paid for most of my stuff
Back then if I wanted parts you either saved forever or went dumpster diving. I still have a mess of gold plated computer IC's from the mid '70's from those expeditions and which paid for most of my stuff
I think as nothing to do, it's just to give micro signals, dielectric absorption of the caps, when changing polarity so it doesn't remember the previous charge.
Some more links
http://www.lansingheritage.org/images/jbl/specs/home-speakers/1993-k2-s5500/page10.jpg
http://www.lansingheritage.org/images/jbl/specs/home-speakers/1993-k2-s5500/page11.jpg
http://www.lansingheritage.org/images/jbl/specs/home-speakers/1993-k2-s5500/page12.jpg
Do you mean about the 9v battery? I'm not sure about technicalities... forgive me.The bias level needs to be greater than the output voltage level. Increase accordingly
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