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Thread: My 4430 project

  1. #1
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    My 4430 project

    Hi,

    so I've decided to keep you informed about my 4430 studio monitor builds. I've collected all necessary parts so far, the drivers, the biradial horns, the passive components. I don't want to go active, mostly due to the unobtanium 5pdt switches.

    If someone feels bored by this thread, please let me know. I'll be stopping it at once. Otherwise, critics are welcome!

    Today I've built the crossover networks. I've bought stock 2.7 mH, 1.8 mH, and 50 H chokes and unwound them until my LCR meter read the required values of 2.6 mH, 1.6 mH, and 40 H, resp. To get the also non-standard capacitances, standard capacitors were paralleled by smaller ones.

    Here's the pair without the controls:

    Name:  20190617_192818_kl.jpg
Views: 220
Size:  156.5 KB

    Then I connected the L-pads and the rheostats:

    Name:  20190617_203430_kl.jpg
Views: 224
Size:  86.1 KB

    Some weeks ago I've shown how I modified an 8 ohms L-pad for a 30 ohms rheo. They're now part of my construction.

    Still I don't get how the 3134 xover works. Somewhere I've read that the 30 ohms rheo opens if turned fully ccw. Now if the L-pad is turned fully ccw at the same time, this would mean that only the 2235H works, and frequency response is limited to 1 kHz with a 12 dB/oct slope. I really can't believe that.

    My rheo's don't open, btw, their resistance is 30 ohms in this case.

    Best regards!
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  2. #2
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    Electrician by Trade?

    Hi Kay,
    That is some impressive work! Really nice wiring! and Layout!
    I am thinking you don't have a Soldering Iron? Would be a great investment and practice heaps before you move onto your
    build. You may need to use some "clips or alligator clips" as Heat-sinks so that the components don't suffer Heat Stress/Failure..
    This [soldering of your joins] will ensure proper electrical connection. Very important.
    Will be watching you're progress with interest!!

    Kind Regards,
    DogBox
    [Steve]

    <PS> What are the Rheostats for? In a Crossover? New one by me...?
    Last edited by DogBox; 06-17-2019 at 07:17 PM. Reason: Query..

  3. #3
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    I'm so disappointed, where are the Wima my german friend!? Just kiddin', nicely done These L-Pads seems complicated BTW, mount it, test, get the values and then go for fixed R?
    Seems it is twisted and then soldered, isn't it? Looks like old amps, wrapped and soldered. A pain in the a.. to remove!

  4. #4
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    Quote Originally Posted by DogBox View Post
    I am thinking you don't have a Soldering Iron?
    Hi Steve,

    why do you think so ? Due to the screw terminals that I've chosen to ease installation in the cabinets? All the other joints were first wrapped and then soldered, of course.

    <PS> What are the rheostats for? In a crossover? New one by me...?
    Have a look at the 3134 schematics that can be seen in my 1st pic. JBL provided them for mid and treble controls.

    Best regards!

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    Quote Originally Posted by Malefoda View Post
    I'm so disappointed, where are the Wima my german friend!? Just kiddin', nicely done
    Frankly, I prefer to buy high quality motor caps and/or class X2 RFI supression caps when they're offered on surplus for cheap. The smaller ones are from various assortments, or I yet had them laying in my bins. Hence the multiple parallels especially for the 6 F and the 14 F caps.

    Seems it is twisted and then soldered, isn't it? Looks like old amps, wrapped and soldered. A pain in the a.. to remove!
    Yes, that's exactly how I did it! Just to avoid any mechanical stress in the solder joints. I certainly don't plan to replace these components, 'cause all of them are overdimensioned and I'm quite sure they'll survive me .

    Best regards!

    Btw, you were the one who had spare 4430 decals some months ago?

  6. #6
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Kay Pirinha View Post
    Hi,

    so I've decided to keep you informed about my 4430 studio monitor builds. I've collected all necessary parts so far, the drivers, the biradial horns, the passive components. I don't want to go active, mostly due to the unobtanium 5pdt switches.

    If someone feels bored by this thread, please let me know. I'll be stopping it at once. Otherwise, critics are welcome!

    Today I've built the crossover networks. I've bought stock 2.7 mH, 1.8 mH, and 50 H chokes and unwound them until my LCR meter read the required values of 2.6 mH, 1.6 mH, and 40 H, resp. To get the also non-standard capacitances, standard capacitors were paralleled by smaller ones.

    Here's the pair without the controls:

    Name:  20190617_192818_kl.jpg
Views: 220
Size:  156.5 KB

    Then I connected the L-pads and the rheostats:

    Name:  20190617_203430_kl.jpg
Views: 224
Size:  86.1 KB

    Some weeks ago I've shown how I modified an 8 ohms L-pad for a 30 ohms rheo. They're now part of my construction.

    Still I don't get how the 3134 xover works. Somewhere I've read that the 30 ohms rheo opens if turned fully ccw. Now if the L-pad is turned fully ccw at the same time, this would mean that only the 2235H works, and frequency response is limited to 1 kHz with a 12 dB/oct slope. I really can't believe that.

    My rheo's don't open, btw, their resistance is 30 ohms in this case.

    Best regards!
    The schematic is quite simple.

    Use tab 2 and tab 1 of an 8 ohm l pad for the HD level trim. This will put an 8 ohm variable resistance in the RCL resonance circuit with a high Q at 16 khertz

    The other Lpad should be wired with tab 2 out , tab 1 to ground and tab 3 in. This L pad controls mid range presence in the 2 khertz region.


    The L pad is not a potentiometer as such but a constant impedance attenuator with a variable 8 ohm series track and a variable 39 ohm shunt track.

  7. #7
    Senior Member Ian Mackenzie's Avatar
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    Why arent you using expensive Mundorf crossover parts and support the local hifi industry?

  8. #8
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    Quote Originally Posted by Kay Pirinha View Post
    Btw, you were the one who had spare 4430 decals some months ago?
    Nope! 4313B owner here (BTW my bro has some 4430 but no spare at all).
    BTW Ian, "Cheap" and "Mundorf" doesn't usually mix well

  9. #9
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    Quote Originally Posted by Ian Mackenzie View Post
    Use tab 2 and tab 1 of an 8 ohm l pad for the HD level trim. This will put an 8 ohm variable resistance in the RCL resonance circuit with a high Q at 16 khertz
    Hi Ian,

    during my measurements for my thread about modifying a L-pad I've found out that the 8 ohms rheostat is between lugs #3 and #2, the 40 ohms is between #2 and #1.

    The other Lpad should be wired with tab 2 out , tab 1 to ground and tab 3 in. This L pad controls mid range presence in the 2 khertz region.
    That's exactly what the JBL schematics tells us.

    The L pad is not a potentiometer as such but a constant impedance attenuator with a variable 8 ohm series track and a variable 39 ohm shunt track.
    Yes, but constant impedance seen from where? In the original schematics the compression driver looks back into a constant source impedance. Is this useful indeed? Shouldn't it preferable for the HP filter to look into a constant load impedance? It's more than puzzling.

    Quote Originally Posted by Ian Mackenzie View Post
    Why aren’t you using expensive Mundorf crossover parts and support the local hifi industry?
    Ha ha ! I'm quite convinced that Mundorf sells parts that are just expensive, and I'm sure that Mundorf parts costs often don't correlate with parts quality. Just with Apple for instance, you just pay for the brand. And thissurely doesn't mean that Mundorf parts are of low quality. I chose Intertechnik (also German) filter chokes, 'cause they were much cheaper than comparable Mundorf's, and I didn't feel any urge at all to buy overpriced Mundorf capacitors .

    Best regards!

  10. #10
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Kay Pirinha View Post
    Hi Ian,

    during my measurements for my thread about modifying a L-pad I've found out that the 8 ohms rheostat is between lugs #3 and #2, the 40 ohms is between #2 and #1.



    That's exactly what the JBL schematics tells us.



    Yes, but constant impedance seen from where? In the original schematics the compression driver looks back into a constant source impedance. Is this useful indeed? Shouldn't it preferable for the HP filter to look into a constant load impedance? It's more than puzzling.



    Ha ha ! I'm quite convinced that Mundorf sells parts that are just expensive, and I'm sure that Mundorf parts costs often don't correlate with parts quality. Just with Apple for instance, you just pay for the brand. And thissurely doesn't mean that Mundorf parts are of low quality. I chose Intertechnik (also German) filter chokes, 'cause they were much cheaper than comparable Mundorf's, and I didn't feel any urge at all to buy overpriced Mundorf capacitors .

    Best regards!
    Hi Kay,

    I have posted an explanation in your other thread on L pad functionality.

    The way these networks perform under real conditions can be ambiguous to the observer.

    The Upper L pad uses Only the series 8 ohm arm of the rheostat not the 30 ohm rheostat as I recall.

    The Lower L pad operates with both the 8 ohm series arm and the 39 ohm shunted arm.

    The high pass filter design calls for a relatively constant load impedance seen by the high pass network.

    The L pad does this with the AC impedance at lower frequencies near the crossover point.

    The AC load impedance seen by the LPad falls with increasing frequency due to the effect of the RCL network. The 20R fixed series resistance offsets this and acts to reduce the full range drive voltage to the compression driver. The series RCL network is a tuned high Q resonance circuit with a peak at 16 khertz. This produces some passive voltage gain at peak Q. The downside of this type of circuit is it creates a low impedance at resonance. The fixed 20R resistance moderates the effect of RCL network on overall load impedance seen by the power amplifier. The 8 ohm series reheostat alters the Q and reduces the peak Q at 16kertz. This forms a high frequency brilliance control above 10khertz.

    The compression driver largely sees the high pass output voltage of the RCL filter at higher frequencies.

    The effect of the lower L pad voltage drive is to back fill the falling amplitude response in the 1-4 khertz region as a result of the series RCL network high pass function in the passband. In the fully clockwise position the response will be elevated in the 2 khertz region forming a presence control.

  11. #11
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    Hi Ian,

    thanks a lot for your explanations !

    Quote Originally Posted by Ian Mackenzie View Post
    The Upper L pad uses Only the series 8 ohm arm of the rheostat not the 30 ohm rheostat as I recall.
    This indeed would make more sense! OTOH, JBL states 30 ohms for this rheo. Just to puzzle copyists like me ? And I'm really quite sure that there's a document somewhere either in the audioheritage site or in the jblpro site saying that this rheo opens if turned fully ccw. I'll search for it...

    The Lower L pad operates with both the 8 ohm series arm and the 39 ohm shunted arm.

    The high pass filter design calls for a relatively constant load impedance seen by the high pass network.

    The L pad does this with the AC impedance at lower frequencies near the crossover point.
    I've been re-thinking for quite a while. You're right. My idea previously has been that the lugs #2 and #3 should have to be swapped to achieve a constant impedance as seen by the HP filter source. But this would demand for an additional 16 ohms resistor between lug #1 and GND.

    The AC load impedance seen by the LPad falls with increasing frequency due to the effect of the RCL network. The 20R fixed series resistance offsets this and acts to reduce the full range drive voltage to the compression driver. The series RCL network is a tuned high Q resonance circuit with a peak at 16 khertz. This produces some passive voltage gain at peak Q. The downside of this type of circuit is it creates a low impedance at resonance. The fixed 20R resistance moderates the effect of RCL network on overall load impedance seen by the power amplifier. The 8 ohm series reheostat alters the Q and reduces the peak Q at 16kertz. This forms a high frequency brilliance control above 10khertz.

    The compression driver largely sees the high pass output voltage of the RCL filter at higher frequencies.

    The effect of the lower L pad voltage drive is to back fill the falling amplitude response in the 1-4 khertz region as a result of the series RCL network high pass function in the passband. In the fully clockwise position the response will be elevated in the 2 khertz region forming a presence control.
    Yes, that's how I also see it. The peak is more in the 12 kHz range, though, due to the voice coil inductance that also forms a part of the resonant circuit.

    Thanks again, Ian, and best regards!
    Last edited by Kay Pirinha; 06-18-2019 at 11:59 PM. Reason: HTML *sigh*

  12. #12
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Kay Pirinha View Post
    Hi,

    Still I don't get how the 3134 xover works.

    Best regards!
    Well if you built it correctly and you are getting the intended result does that matter.

    Ive used theses horns on and off over the past 20 years years and l am looking at the schematic in Spice and it works nicely.

    Just curious as to what you dont understand?
    When someone questions a Jbl design its because they failed to execute it correctly.

    Below the paper on this monitor design and image of control adjustments
    http://www.cieri.net/Documenti/JBL/D...)%20(1983).pdf
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