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Robh3606
04-22-2003, 08:35 PM
I am going to change to a passive compensation for my 2344 horns. I am using the 4435 crossover and figured I would give it a try. I have schematics for several of them so the conversion looks easy with them as a reference and the information in the brochures on the site. Any of you tried to build/convert one or have any experience with them??

Thanks Rob

Ian Mackenzie
04-23-2003, 03:59 AM
Yes,

Affirmative Will Robinson,

Use the exact values JBL state, this will result in a smoother axial response within 3 db from 1 - 18 khz.

Trying to design your own is a cow. Don't attempt it.

I assume you are bi amping, so remember to use a hefty series non polarised capacitor to protect your compression drive(40uf).

The concept of the charge coupled capacitors may yield some improvement as the series protection capacitor will need to be large, about 40 uf. This concept may help improve resolution. These capacitors can also be bypassed with 0.1 uf or smaller film foil types for improved performance.

The components for the nominal crossover can be omitted.

It is recommended that you include the pads to ensure the correct accoustic drive to your compression driver.

The pads serve two purposes.

The main 8 ohm pad controls the level +- 4db in the 2 khertz zone and is necessary to ensure the correct operation of the equ network. The pad in series with the equ network provides adjustment of the top end response.

I would recommend quality capacitors like the Auricap or the Hovlands if you can in the equ netwrok, these will extract the best performance without the need to bias a lesser capacitor.

Your graph should look like this, enjoy.

Ian

This graph is the 2122 H & 2344 with 2420 + Ti diamond bottle top at 9 ft mid way on axis with the 2122H and 2344 in my listening room.

The mic is a Panasonic insert on a 3 ft aluminium tube with a custom battery mic preamp feeding WinAirr FTE driving a PC Sound card in the HP Pavilion 723A 2.0GHz.

Robh3606
04-23-2003, 05:59 AM
Hello Ian

I have a complete parts set to build from. I plan on taking your sugestion and doing it complete from the start. When I did my own comps they were good but not as good as the JBL 44xx crossovers. I always had a slight hump and the last octave was always lower in amplitude than it should have been. Sounded good but not really there. I will be biamping so I don't have to worry about the woofer sensitivity like when I was running passive crossovers. That prevented me from building the original networks to begin with. I already had the 40ufs sitting around not used so I needed 4 5uf caps the resistors and a 9 volt batery and I am there. Just got the 5uf's just have to purchase the resistors. Let you know how it works out.

Regards Rob

Ian Mackenzie
04-23-2003, 06:23 AM
Rob,

Cool,

Have fun.

Ian

here's another graph, not as pretty, the blimp @ 15 khz is my TV Set.

Ian Mackenzie
04-23-2003, 06:32 AM
Hey Rob,

Tell us about the lastest on that sexy 4 way system in your avatar

Ian

Robh3606
04-23-2003, 09:29 PM
Not much to tell really. They were up in the den for a while. They are in storage at the moment until things get settled. I miss them and they were fun to build. Probably never find another NOS XPL200A crossover and 093TI mids again. I have a pair of ferrite woofers I want to try in them.

Rob :)

Earl K
04-24-2003, 07:23 PM
Hi Rob

I'd love to hear about your sonic impressions after trying out JBLs' Charge Coupled Crossover topology. Considering the extra cost ( twice the quantity of caps & twice the mf value ) I wonder if its real positive benefit . Especially when compared to "transcapping" which is so economical . I haven't done it, as I'm still trying to decide whether to give titanium diaphragms ( on exponential horns not CD ) an "oil bath" ( inline or in the motor gap ) to dampen them down to the level of aluminum . I do remember that 2 years ago I did some testing comparisons and found that adding so called "fast caps" exacerbated things that I didn't like about 2426s on exponential horns. Seemed to add to an "overshoot" problem ( ie; unterminated transformer ) . But, "ADD" kicks in way too often these days and I just go back to my 288s for comfort . :o
( I think radio contolled relays toggling these things in and out of the circuit is the way to go to give a form of "blind taste-testing " ) .

regards <> Earl K :)

Robh3606
04-24-2003, 08:09 PM
Hello Earl


"I'd love to hear about your sonic impressions after trying out JBLs' Charge Coupled Crossover topology. Considering the extra cost ( twice the quantity of caps & twice the mf value ) I wonder if its real positive benefit . Especially when compared to "transcapping" which is so economical ."

Be glad too. I am very curious myself. They use it in most of the statement systems and the L250 Jubilee so there must be something to it. I already had the most of what I needed so I figured what the heck why not try it.


( I think radio contolled relays toggling these things in and out of the circuit is the way to go to give a form of "blind taste-testing " ) .

You are reading my mind on that. I want to have a switch to drop the battery in and out. Just wondering what the time constant would be to bleed off the charge. May not be a quick on off thing.


"oil bath" ( inline or in the motor gap ) to dampen them down to the level of aluminum

Whats that??? Kind of like ferrofluid except not???

Rob :)

Earl K
04-25-2003, 05:30 AM
Hi Rob
"In the gap" would be ferrofluid & "InLine" would be big AC Motor Run style caps. As I said , I haven't pursued this , my interest iin this area is pretty dormant at this time . I'm satisfied with the "type - unknown" caps that I now use for DC blocking duties.

re the ferrofluid; I have a pair of Selenium D205Ti 1" driver. It has a titanium diaphragm, uses an Altec style radial phase plug and has ferrofluid in the gap. The first time I heard these drivers I was surprised at how smooth sounding they were ( on small exponential horns ) . Testing revealed significant response dips/holes centered at @ 2.5 & 5 K ( right there that means I can't recommend others buy them ). My initial aural satisfaction was likely a reaction to these response nonlinearities as much as anything else . But the experience did get me thinking about using a bit of ferrofluid in gaps of drivers/horns which I feel are underdamped. Ferrofluid (like motor oil ) comes in many weights & blends. One needs the experience or guidance of others to help select the weight, the quantity , advice on clean-up, paper contamination realities & the need ( or not ) for extra gaskets. I shelved acting on the idea till more info presents itself .

The ( A/B ) cap testing I did used toggle switches to flip the different types in and out of the circuit. This was while listening to just the compression drivers .

regards <. Earl K

Ian Mackenzie
04-25-2003, 07:42 AM
Great to see some diy tweeking happening.

Tell us all know how it goes,

Ian

4313B
05-07-2003, 02:39 PM
Ok "Robh3606" ;), after several conversations I'm sold. :)

I will probably start out charge coupling a pair of stock JBL networks that employ the standard metallized mylar and non-polarized electrolytic capacitors bypassed with polypropylene and polystyrene topology such as used in the original 250Ti. (polypropylene excels in speed and dynamics, polystyrene excels in spaciousness and three-dimensionality)

I will then move up to polypropylene and foil capacitors without bypass capacitors. I can always add in polystyrene and foil bypass capacitors if the polypropylene and foil capacitors prove to sound too "compressed". However, by charge coupling, the limitations of the various dielectrics is theoretically supposed to be greatly reduced (as is overall distortion). Using a high quality film that will hold the charge is important, so I'll go with polypropylene and foil. The results are alledged to be stellar.

4313B
05-07-2003, 02:51 PM
An Example

4313B
05-07-2003, 03:09 PM
4348 innards with the charge coupled network designed by Greg Timbers.

Yeah Baby!

Robh3606
05-07-2003, 04:52 PM
Hello Rob

I will be using the same capacitor combo as you. Glad you are giving it a try too. Maybe by the end of the week I can have one cobbled together. Those 40uf's are big mothers! Got some project boxes to but it all in but will probably have to strap those on!

Rob:)

mrdsp
05-09-2003, 08:51 PM
Help... Giskard.

Do you have any references which can explain in simple terms the theory behind transcapping. Is this an earlier attempt to deal with "limitations of various dielectrics"? On the surface it would seem that transcapping is a variation of bypassing a capacitor with a smaller one in order to negate the effects of series inductance (ESL) and/or resistance (ESR) of the larger device. If so it would then seem that charge coupling would greatly increase the ESL and/or ESR:confused: , yet the results are reported to be better. One might ask the question whether paralleling that charge coupled pair with a pair of 0.02 uF capacitors in its own charge coupled configuration would improve things further. Thanks!

Robh3606
05-10-2003, 06:54 AM
Hello

Can't answer the question but for what its worth the 9800 uses a Charge Coupled network that uses transcaping. The 4344 2 uses a CC network without?? I am going to build them with them.

Rob

Earl K
05-10-2003, 07:18 AM
Hi mrdsp

I know you asked for references for "transcapping" , sorry, I can't help you there. For a reasonable laymans explanation of the benifits of charge-coupling, go and read the JBL K2 S5500 Product Overview (http://www.lansingheritage.org/html/jbl/specs/home-speakers/1993-k2-s5500.htm) . The overview info found there, "sells" the concept quite well. With Class A amplifiers being back in vogue, JBLs' "balanced capacitor" approach is in synch with current wisdom on the subject.

regards <. Earl K

4313B
05-10-2003, 08:37 AM
Originally posted by mrdsp
Help... Giskard.

Do you have any references which can explain in simple terms the theory behind transcapping. Is this an earlier attempt to deal with "limitations of various dielectrics"? On the surface it would seem that transcapping is a variation of bypassing a capacitor with a smaller one in order to negate the effects of series inductance (ESL) and/or resistance (ESR) of the larger device. If so it would then seem that charge coupling would greatly increase the ESL and/or ESR:confused: , yet the results are reported to be better. One might ask the question whether paralleling that charge coupled pair with a pair of 0.02 uF capacitors in its own charge coupled configuration would improve things further. Thanks!

Well, JBL literature is full of little blurbs about bypass capacitors. Basically the large main capacitors (metallized mylar and NPE) introduce a slight time lag (hysterisis/dielectric absorbtion). The much smaller bypass capacitors (polypropylene or polystyrene) are much more linear and help to greatly reduce this. The theory was borrowed from advanced circuit design and was first incorporated in the L110A. Nearly all JBL loudspeakers since the L110A have incorporated this topology as SOP. Some of the statement systems, such as the 250Ti, used both polypropylene and polystyrene to increase both dynamics and spaciousness. There was a website that showed the differences in linearity between the different dielectrics but I can't seem to find it any longer. In any case, teflon, polypropylene and polystyrene are among the most linear while mylar and NPE's are lower down on the list.

Expense and size are also of consideration. A good metallized mylar main capacitor (usually superior to just mylar (polyester)) bypassed with a polypropylene or polystyrene is a very cost effective way to achieve nearly the same performance of a high quality polypropylene main. It's also a smaller package.

These days there seems to be as many different dielectrics and differences in quality between the same dielectrics as there are theories on how to use them. Some expand on the bypass theory and think cascading is the best solution. Others feel that the finest film and foils completely negate the need for bypassing at all. Quality is another issue. Just because a capacitor is film and foil doesn't necessarily mean it is automatically superior to metallized. One brand of metallized polypropylene may be preferred over another brand's more expensive film and foil, etc. The various combinations of dielectrics either work or don't work, and only experimentation will dictate which falls in which category.

This is one reason why I have advocated simply using the stock JBL bypass capacitors. No, they aren't the best that are out there but they have been chosen to offer the best price/performance with the stock mylar and NPE capacitors JBL has used over the years. In other words, the R&D has already been done. They are the most economical in both time and money. A person embarking on a mission to find a better solution has to be aware of the time and money involved. Not every polystyrene sounds the same, not every metallized polypropylene sounds the same, etc.

As for charge coupled theory, Earl has posted the link for a decent cover of the subject.

4313B
05-10-2003, 09:05 AM
Originally posted by Robh3606
Hello

Can't answer the question but for what its worth the 9800 uses a Charge Coupled network that uses transcaping. The 4344 2 uses a CC network without?? I am going to build them with them.

Rob

Hi Rob,

After further conversation it has been suggested that one start off using polypropylene mains without bypass capacitors. If one HAS to use mylar or NPE, those will have to be bypassed. If one HAS to use NPE, at least 10% of the total value should consist of polypropylene.

Robh3606
05-10-2003, 11:31 AM
High Rob

OK Thanks

Rob:)

4313B
05-10-2003, 12:36 PM
I've been looking at some of the large format 4-ways and the capacitor values get daunting :(

One thing I would like to revisit is a charge coupled high pass on a 2405/077. Those things respond so well to polypropylene and polystyrene bypass caps the charge coupled approach could be very interesting. Maybe I'll have to toss a pair of 077's at a pair of LE8T-H's just like old times :)

4313B
05-10-2003, 01:57 PM
Oh, I also forgot to add that it is probably best to use the capacitors at least for 48 hours before installing the battery. This allows them to "break in" and also allows one to become quite familiar with the program material one will be using for comparison. Once that period is over and one connects the 9V battery one should begin to hear a difference as the battery charges the capacitors. The resistors used should be 2.0Mohm to 6.0Mohm. The capacitors need to charge slowly. The batteries should last as long as their shelf life since no current is being drawn from them.

Some people have stated that series capacitors are "more important" than parallel capacitors, in "real life" this is false. So charge coupling only the series capacitors and leaving the parallel capacitors "normal" isn't a brilliant idea.

mrdsp
05-11-2003, 04:31 PM
Per the groups recommendation I read the K2-S5500 discussion about charge coupling. I was aware of the piezoelectric nature of capacitors, but from a reciprocal point of view. I have had ceramic capacitors induce tiny voltages from microphonic effects (ala condenser microphones) in feedback loops for amplification stages which is why I don't use them for that application. I was not aware that voltage biasing them could make film capacitors be and sound "tighter" (re: K2-S5500 brochure). In my speakers the crossovers are mounted in the woofer area. I can certainly imagine that it gets quite noisy from the capacitors point of view and that the vibrations may affect its physical "tightness". It makes me wonder if I should attempt to isolate the crossover in a sound tight box or am I making a mountain out of a molehill?

4313B
05-11-2003, 05:11 PM
I think the network is isolated in the K2-S9800.

MJC
05-18-2003, 10:12 PM
I will probably start out charge coupling a pair of stock JBL networks that employ the standard metallized mylar and non-polarized electrolytic capacitors bypassed with polypropylene and polystyrene topology such as used in the original 250Ti. (polypropylene excels in speed and dynamics, polystyrene excels in spaciousness and three-dimensionality)

What website did you use to purchase polystyrene capacitors?

4313B
05-19-2003, 03:26 AM
http://www.capacitors.com/index.html
http://www.welbornelabs.com/rel.htm
http://www.percyaudio.com/
http://www.soniccraft.com/
http://www.partsconnexion.com/
http://www.hndme.com/
http://www.partsexpress.com/

Look for AudioCap Polystyrene-&-Tin Foil Series RT or MultiCap Polystyrene Series RTX

I think you can still get 0.005 uF polystyrene capacitors from JBL Pro Parts

Ian Mackenzie
07-29-2006, 08:39 AM
I am in the process of ordering some Solen capacitors to build a 3145 Equivalent Charge-Coupled Network per the recommendations above.

I will post progress on the project in due course.

Ian

MJC
07-29-2006, 10:54 AM
I am in the process of ordering some Solen capacitors to build a 3145 Equivalent Charge-Coupled Network per the recommendations above.

I will post progress on the project in due course.

Ian
My experience with using Solens in a CC network produced very good results, indeed.

Robh3606
04-24-2010, 03:39 PM
Bump

Rob:)

badman
04-27-2010, 11:46 AM
http://www.madisound.com/catalog/product_info.php?products_id=1463


I just ordered 100 of these, as a 10uF connection will require 4, and a 20uF 8, and so forth- I anticipate being able to burn through them pretty quickly. Naturally they're not useful for smaller values, but the potentially massively paralleled larger values should have some performance benefits outside of the charge coupled dielectric.

All values will have greater power handling than the smaller cap without charge coupling (2 larger caps with 2x the plate area each=6dB more power)., and anything over the nominal value of the individual parts used for the series/parallel network will begin to see improvements in ESR and ESL as well.

I'm looking forward to giving it a try, I have a lot of caps invested in notch filters and such.

JuniorJBL
04-27-2010, 09:00 PM
Yes I too have purchased lot's of 100's from Madisound. Got the .33's and the .68's as well.
Good way to test out your designs.:)