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Thread: JBL L300 / 4333 3 way analog electronic crossover question

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  1. #1
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    JBL L300 / 4333 3 way analog electronic crossover question

    There is another active thread on using a JBL L300 with an electronic crossover but I want to confirm a couple of things that are unclear to me.
    I've finally scrounged the parts to build my non-original 4333 with some utility cabs I purchased a while ago.

    I will be using:
    2405
    2311/2441/2445 diaphragms
    2235
    Marchand 3 way XM9 crossover 24db/octave
    DC blocking cap / 20 ohm shunt resistor across 2405 and 2441
    No L-Pads (will control volume in each speaker from either crossover or amplifiers

    Just want to verify before hooking up
    1. All the above drivers have black as their + terminal
    2. The 2441 signal should be inverted compared to the 2405 and 2235 (as shown in the Nelson Pass schematic).

    I appreciate any help.
    Best Regards,
    gwho

  2. #2
    Administrator Mr. Widget's Avatar
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    Sounds like a cool project!

    Question: What are the 20 ohm resistors for?

    A thought about polarity: Some amps are inverting and others are noninverting. Recently I was helping a friend dial in his tri-amped system and I noticed a massive suck out at one of the crossover frequencies. This was because one of his amps was inverting the phase. Finding this kind of thing as well as balancing your system are best done with some form of measurement system.


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    The original crossover topology in the 4333 was not 24db per octave 4th order filters . The Nelson Pass crossover schematic shows 2nd order for the low and mid and 3rd order for the high. The summing will be substantially different with 4th order filters. You will likely have to determine the best polarity empirically by listening or ideally using test software like Smaart, Foo or REW.



    Quote Originally Posted by gwho View Post
    ...

    Just want to verify before hooking up
    1. All the above drivers have black as their + terminal
    2. The 2441 signal should be inverted compared to the 2405 and 2235 (as shown in the Nelson Pass schematic).

    I appreciate any help.
    Best Regards,
    gwho

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    Riley / Widget,

    Thank you for the responses and encouragement. I will definitely try to take some measurements after putting them together. Just want to get an idea of a starting point.
    I will now assume that I will try it both ways and determine what works best. I've attached a couple pictures of the boxes. They are not perfect but good enough.

    Name:  front_4333.jpg
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    The 20 ohms resistors discussed in one of the threads I read for electronic crossovers where they recommended a DC blocking cap and a shunt resistor across the CD inputs (is this wrong?).

    Regards,
    Gary

  5. #5
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by gwho View Post
    The 20 ohms resistors discussed in one of the threads I read for electronic crossovers where they recommended a DC blocking cap and a shunt resistor across the CD inputs (is this wrong?).
    Not sure why you would need the resistors, I have never used them. I use a very large value cap in series with my compression drivers as protection, but thats it. I am a fan of less is more.

    The cabinets look fine. You can even veneer them at some point if you want.


    Widget

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    I won't put in the resistors. I agree less is better.

    Regards,
    gwho

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    Senior Member macaroonie's Avatar
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    In my experince it's fairly apparent which way is correct. It might take a little while as you get levels adjusted etc but it only takes a minute or so to switch phase on an amp. you will have a eureka moment.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by macaroonie View Post
    In my experince it's fairly apparent which way is correct. It might take a little while as you get levels adjusted etc but it only takes a minute or so to switch phase on an amp. you will have a eureka moment.
    Maybe for a trained/experienced listener like yourself. I have heard so many DIY setups that were so very wrong. Basic measurements make it a lot easier to get in the ballpark. Once there, subtle tweaking to taste can be very rewarding.


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    Widget,

    Thank you for that information. I will consider it in the future. I was contemplating putting a 10" woofer on top of the box if I did not like the sound of the 4333 or just to try it (I know another crossover). I was able to pick up a couple of 2251J very inexpensively so they were my back up plan.

    Happy New Year
    gwho

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    The whole 15" woofer crossing directly into a compression driver type of speaker design is a very 1950s way of approaching a world of 15 watt tube amps. As transistor amps became more powerful three way designs with cone driver mids crossing into compression drivers above 1k hz made for much better sounding speakers. Putting a ten between your 15 and your one inch will likely make for a much nicer sounding box. The ten can be in a small sealed box and crossed into at 400 hz. This among other things means that 40 hz movement of the woofer cone aren't modulating the 1200 hz tones from the same driver.

    Quote Originally Posted by gwho View Post
    Widget,

    Thank you for that information. I will consider it in the future. I was contemplating putting a 10" woofer on top of the box if I did not like the sound of the 4333 or just to try it (I know another crossover). I was able to pick up a couple of 2251J very inexpensively so they were my back up plan.

    Happy New Year
    gwho

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    Is it possible to get the 2216 woofer? I assume they are probably very expensive.

    Regards,
    gwho

  12. #12
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by gwho View Post
    Is it possible to get the 2216 woofer? I assume they are probably very expensive.

    Regards,
    gwho
    There are two versions of this driver. I have not played with them myself so I can not say whether the 2216ND or the 2216ND-1 will be better in your application, but they are available and while on the expensive side, they are not refi expensive.

    https://reconingspeakers.com/product...bl-m2-5041785/

    https://reconingspeakers.com/product...-320-0045-002/


    Widget

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    At a minimum I can take a measurement with a DEQ2496 and pink noise to determine what the response of the speaker is. I will likely also try to learn how to use REW if time permits and take some measurements.

    Best Regards,
    gwho

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    REW is a pretty remarkable piece of software particularly for free. I've used measurement software since the original Crown TEF machines and I have SpectraFoo and Smaart licenses and I still use REW for some things. Well worth the time and effort to learn. The RTA in the DEQ ( well any RTA really ) isn't worth much in assessing speaker performance although it is handy for ear training.

    Quote Originally Posted by gwho View Post
    At a minimum I can take a measurement with a DEQ2496 and pink noise to determine what the response of the speaker is. I will likely also try to learn how to use REW if time permits and take some measurements.

    Best Regards,
    gwho

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    Riley,

    Thank you for that information. I will definitely try that at some point. From reading in the forum it appeared that there were varying opinions on where you could cross (800hz - 1.2Khz) the 2311/2441 to the 2235. Some said you can cross the 2441 at a lower frequency because of the larger diaphragm. Other said you couldn't because of the 2311 horn. I never could find a definitive answer which is why I purchased the JBL 10" speakers just in case.

    Regards,
    Gary

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