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Thread: Pieceing together a JBL 4350 build in Australia

  1. #31
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    Quote Originally Posted by Ian Mackenzie View Post
    Itís a bit technical.

    In simple terms a passive crossover in this particular loudspeaker design would cause significant power losses in the crossover, loss of damping on the woofers and the mid cone. The motional impedance of the mid cone and woofer may interact causing sub optimal voltage drives in the crossover region. The effect is modulation of the voltage drive and muddle sound.

    Bi amping eliminates the problem and allows a significant improvement in dynamic range and clarity.

    If you were to attempt a passive crossover it would be expensive and disappointing compared to bi amping
    Definitely beyond my understanding but I trust your knowledge. I don't have the ability to design a passive network, it was more of a "I wish" statement. I hated biamping my factory 4350's, it complicates everything and there is a lot more cables running about. I have a DEQX and Bryston 10B to handle the split but will require another SS amp for bass duty.

    Still excited for the build.

  2. #32
    Senior Member Ian Mackenzie's Avatar
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    Cool

  3. #33
    Senior Member DogBox's Avatar
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    4350 Parts, Crossover Schematic,etc.,

    Quote Originally Posted by kelossus View Post
    Definitely beyond my understanding but... will not be above the learning experience!

    Still excited for the build. And so you should be!!!
    Hi Kelossus,

    I thought that was the name of a British Speaker, by Fane [but spelled with a C..]? Nevermind.. I was wondering how you are off for the
    necessary Parts besides the Boxes you seem to have? Being in Australia, some of these things can be hard to track down and that the USD=AUD exchange
    rate isn't the best at the moment, can make things expensive. $$$$
    I may have a few spares if you'd like to send a PM and let me know what you are short on. You can also get in touch with Edgewound [Ken] who will be the
    best one to see about recones if needed. I also have a copy of the schematic if needed.
    This will be a nice Project to follow being done down under!

    Kind Regards,
    DogBox [Steve]

    ...

  4. #34
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    Yes,

    Well;;

    If I had empty 4350 boxes that I wanted turn into something listenable > this is the direction I would go.

    This close-up is from an article detailing a bit of what went on making Paul Simons ground-breaking album, "Graceland".

    You can call me Al - A visit to Downtown (Ovation) Studios in Johannesburg



    That 2121(a)H would get replaced by a 2123H ( the little brother to the 2202H ).

    Granted, the ATC 3" mid would be harder to source >> though not impossible to find.

    The resulting speaker would be somewhat like a rough precursor to the studio excellent CF2000 ( made by a Canadian company back in the 1980's + 90's ).

    Here's Drake's setup ( apparently ) using CF2000 ( and one of the baby-brother models > CF750 hanging underneath ) ;



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  5. #35
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    Got the boxes. That is also 6x 2235H brand new in the box.

    I have everything besides the 2450 compression drivers. I stupidly bought the 2450SL only to find out they are a 1.5" exit.


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  6. #36
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    Just a quick question, if I were to use the Radian or 2450SL diaphragms in the compression driver would I need to tweak the 4355 network?

  7. #37
    Administrator Robh3606's Avatar
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    Hello

    There will be a bit of a difference but depending on where and how much there is it may not matter.

    The CD in that system is run through a narrow range bandpass filter. That works in you favor as the are all typically designed to have smooth response through that part of the spectrum.

    The horn is non CD so no horn compensation to worry about.

    Asside from a change in level or a potential tilt in the response I would think you should be OK.

    You should have more than enough trim in the pots to compensate for any changes.

    The only way to know for sure would be to actually measure with the horn mounted to your baffle board for the original vs the new diaprhram.

    Non coated vs coated should be fine. Radian vs JBL ????? I have never used them so no measurements I have to compare the differences.

    That said I would expect them to be very similar to the JBL's as used in this system. JMHO

    Rob
    "I could be arguing in my spare time"

  8. #38
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by kelossus View Post
    Just a quick question, if I were to use the Radian or 2450SL diaphragms in the compression driver would I need to tweak the 4355 network?
    Rob is spot on.
    Please see my response to your pm.

    You can try a 1.5 to 2.00 adapter. They are sometimes on EBay

    Your project looks great. Enjoy. When l get back to Noosa we must catch up.

  9. #39
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    So the 2450SL diaphragms are out of the pickings. I just remembered they are 8 ohms and I would rather not tweak the crossover to suit them.

    If you had to choose between used 2441 diaphragms which appear in good condition dated 1990, or brand new Radians. Which ones?

  10. #40
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by kelossus View Post
    So the 2450SL diaphragms are out of the pickings. I just remembered they are 8 ohms and I would rather not tweak the crossover to suit them.

    If you had to choose between used 2441 diaphragms which appear in good condition dated 1990, or brand new Radians. Which ones?

    Radian.

    If you read the Radian tech doc they are claimed to be a direct equivalent to the original jbl diaphragms and are the preferred choose by studios still using these legacy monitors.

    Those factory jbl diaphragms might have signs of fatigue.

    Btw with that 2450SL driver you have other possibilities with more contemporary jbl wave guides.

    Robert S (Europe) can give you plenty of factual advice on horn and wave guides if you decide to go that way eventually.

    I donít have enough bandwidth to look at the start of your thread. Do you have the original jbl crossover for the 4350 or are you making a 4355 crossover?

    Edit. Got to the start of your thread. Lots of options. I think placing the enclosure on its end could be advantageous as the lowboy enclosure can sound dull on the floor.

    In broadcast applications the 4350 was flown over head and inverted with the woofers were at the top.

    With the enclosure on its end you have the midrange and horn up higher and only one woofer coupling to the floor boundary. So subjectively that might be preferable depending on your room.

  11. #41
    Senior Member 1audiohack's Avatar
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    D16R2451SL

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  12. #42
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    At 15lbs do you think the 2311+2450 combo is too heavy to swing off the baffle without a brace?

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  13. #43
    Senior Member Odd's Avatar
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    It can be risky.

    Originally 2441 was attached with a bracket.

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    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  14. #44
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    The 4350/55 used a bracket that attached to the inside cabinet brace. The 2440 is at least twice as heavy as the 2450. It wouldn't hurt to support it especially if they are ever going to be moved say in a truck. I have 2425's on 2307's in my 4344 that are just supported by the horn no issues but I would remove them if I ever transported the cabinets.

    Rob
    "I could be arguing in my spare time"

  15. #45
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    For a home stereo cabinet that doesn't get bumped around it's very unlikely to be a problem. That said JBL portable systems support their compression drivers with a yoke, a simple piece of plywood with a hole cut out to fit the diameter of the driver with the board attached to the nearest cabinet usually the top so no need for custom metal work.


    Quote Originally Posted by kelossus View Post
    At 15lbs do you think the 2311+2450 combo is too heavy to swing off the baffle without a brace?

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