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Thread: Charge Coupling on the Cheap

  1. #196
    RIP 2011 Zilch's Avatar
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    No BS!

    Quote Originally Posted by Ian Mackenzie
    Charge-Coupling: What does it do?

    There appears no conclusive study on the subject supported by reseach and science.

    However, it would seem that turning on the voltage potential does something. As to exactly what that will take some figuring and a more intensive analysis than I really have time for at the moment.
    Quote Originally Posted by Zilch
    I believe it's zero-crossing.

    So long as the peak-to-peak voltage of the signal is less than 18V, the charge on the "plates" never reverses.

    Think of it as Class A operation of capacitors....
    Quote Originally Posted by Rudy Kleimann
    I agree, Zilch. Only thing is, where are you getting 18Volts?
    Quote Originally Posted by Zilch
    Battery biases at 9V.

    Signal is AC.

    It'd take an 18V P-P signal to drive the cap tiepoint to 0V.

    That's plenty loud for compression drivers....

    40.5 peak W across 8 ohms, 20.24 W RMS, no?

    Been wanting to do this for months:

    'Scope on bias connection of biased NL200t3 crossover, main HF cap(s).

    Playing pink noise 85 dB @ 2 M.

    2 V/div vertical, 2 ms/div horizontal.

    Bottom of screen is -1V.

    Zero crossing'd be middle of bottom major division.

    Swings @ 9V +/- 2V, according to design.

    That'd be 2 Watts peak into 8 Ohms at this point. 6 dB of attenuation after that, tho.

    [SEE, we DID have LEDs back in the olden days, and they're still runnin' today.... ]
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  2. #197
    Senior Member JBLnsince1959's Avatar
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    Quote Originally Posted by Ian Mackenzie
    I'll let you know what happens
    please do

  3. #198
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    Exclamation

    This is an old but interesting thread.

    I have decided to revive this thread for those who are interested to in a low cost diy project over the Christmas break. This is for those days when you’ve had enough of the relatives and you want to escape to the workshop or the basement for some space!

    1. Select a loudspeaker on your collection or one you’d like to build up for fun.

    Find a multi way loudspeaker, not necessarily a JBL loudspeaker and let’s see if we can improve the sound out of the horn and tweeter. So what we want to do explore this charge coupled crossover approach on a budget. We’ve not going blow the entire holiday budget on a couple of crossover networks here. Your also going to gain some real insights on how to figure things out along the way.

    As a primer l have decided to test out some of my older drivers in my main system to see what they can do. I have pair of mint LE85 compression drivers and plan to use them in place of my acquaplas coated titanium drivers. This will resemble to an extent the legacy 4343 system in my situation. I am also going to charge coupled the mid range and the slot radiator.

    Of course you can do this with any loudspeaker in your collection. It might be a Decade L26 or a pair of 4312’s.
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  4. #199
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    2. Crossover schematic and change coupled capacitor values

    The next step is to find your crossover schematic of that loudspeaker. If it’s not on Google it probably doesn’t exist!

    Then you need to redraw that schematic with the capacitor values for a charge coupled crossover network. The way it works is that whatever the value is in uF on your schematic multiple that by two. That value is going to be the value of the parts you need.

    For example if you have 1.5uF you need two 3.00 uF capacitors. Sometimes the preferred value won’t be exactly what of you need. Here 3.3uF we can live with. Two 3.3 uF capacitors will give 1.65 uF. If the values you need are not available then use your Smartphone calculator 1X function as follows:

    1/x +1/x = 1/X Sum. Then take the 1/X Sum and use the 1 / X function again.

    This will give be you the value of two different capacitor values = C uF. By adding the 1/X values together then again take the 1/X of the sum it will give you the actual capacitor value of two different values of capacitors.

    I will draw this up on a schematic for you as an example
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  5. #200
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    3. Finding the parts
    Because we are doing on a budget the first place to look in in your parts bin or junk box.
    To make this low cost l have decided to use non polarised 100 volt electrolyte capacitors for the midrange and horn crossover filters.

    Normally in a hifi loudspeaker we would use hifi grade polypropylene capacitors in single units. Because we need two of double the value that is an expensive proposition. Instead we are going to apply the charge coupled crossover approach and improve the performance of these bipolar capacitors with a polypropylene bypass capacitor of 0.01 uF. What l have found in my parts bin are some Wima film foil FKP2 polypropylene capacitors rated at 100 volts. In my parts bin l also found the inductors. I bought the non polarised capacitors from Jaycar a local electronics shop along with some power resistance. I found some Wima FKP10 metalized film foil capacitors for the slot radiator crossover filter.

    My take on this and l’ve seen it used on JBL production is use the electrolyte bi polar capacitors for the large values in the midrange and horn crossover filters. Bypass those values with the 0.01 uF polypropylene capacitors.

    For the tweeter use a Mylar film capacitor or a metalized polypropylene capacitor. Bypass these capacitors with the 0.01 uF polypropylene capacitors.

    For frequencies below 300 hertz you don’t need to use the charge coupled approach. Simply bypass with a 0.01 uF capacitor if you wish.
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  6. #201
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    4. Let’s talk about who’s who in the zoo

    As you might be aware or have seen JBL use Solen 250 volt Fast Capacitors in their flagship loudspeakers. They buy those parts by the 1,000 or more and get an OEM factory price. They are not paying the RRP prices on the Parts Express online catalogue. As a manufacturer/ professional with an ABN l get 25-30% discount. I still find it very very expensive to build up a Solen charge coupled network for those interested! I always offer alternatives at a lower cost.

    There are other alternatives that work very well including bypassing Clarity SA grade capacitors with Auri cap 0.01 uF capacitors. I’ve had some very feedback on that alternative.

    But to make it clear this a diy project on budget for fun. You might be very surprised just how good it sounds.

    While l was out l sent Bunnings (Lowes) and l found some small sheets of hobby plywood to mount the parts on. You can attach these parts in a number ways with hot melt glue, super glue or other adhesive. In my next post l’m going to explore different ways of connecting the pa

  7. #202
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    5. Our Budget
    So far l have bought spent:
    $1.98 on each plywood board
    $20.00 on twelve bi polar capacitors
    $9.00 on the ten power resisters.
    So l have spent about $30 bucks

    I already have the L pads so l don’t need buy those and l have the same inductors in my parts. On modern multi meters you will find it might have a C u and I inductor meter function. This is helpful where you might need to wind off a few turns to obtain the correct value in mH. Similarly you can check your capacitor values.

    You can obtain these 0.01 uF small value polypropylene capacitors from most electronics shops. Polycarbonate or Mylar (Green cap) can get used to get you project going.

    To be continued

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