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Thread: 2445J/2380 + 2404H passive xo help

  1. #31
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    Okay l will see what l can do.

  2. #32
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    JBL 2450J on 2380A, 1m on axis measurement file: JBL2450J_2380A_axis_1m.frd.txt


    Phase correspond to impulse response shift to 0, which means that if using it as it is it will not reflect the delay between 2445 and 2404H, especially if 2404H will be enclosure face plate aligned to the 2380A such in JBL 4750A. Nevertheless using directly as is the xover schematics of 47xx serie:
    http://www.jblproservice.com/pdf/Sou...ries/4750A.pdf
    http://www.jblproservice.com/pdf/Sou...ries/4755A.pdf

    Just attenuating JBL 2450J by 4dB (should be 6dB, but my two measurements where not aligned in SPL), as in 475x loudspeakers there are two 2404H, and it works in simulation. Ideally, a phase shift should be added to the compression driver to reflect delay due to the depth of 2380A.
    Name:  JBL2450J_2380A_2404H_xover_schema.jpg
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    Name:  JBL2450J_2380A_2404H.jpg
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  3. #33
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    I unfortunately could not get the files to work in Leap.

    That’s an interesting option above.

    What he could do is use one of Jbls passive crossovers for the woofer and horn and use the mini dsp to evaluate different options for the 2380 crossover to the 2404.

    That could include delay to the 2404.
    An important point is any digital delay will only work for one 3 D point in space (X, Y, Z position).

    Perhaps more important at a basic level is a smooth crossover transition on axis with the listening position as that will also be dependent on the location of the 2404 (X, Y, Z) regardless of a mini dsp or passive solution.

    (This assumes the mini dsp is only two way.)

    It’s a quick and easy way to assess the subjective behaviour of the 2380 and the 2404 which the graphs don’t tell him. He found that out attempting to EQ the 2380 flat for Hf extension. The graphs don’t necessarily tell you if it will be palettable to the ear.

    He can then work out a passive crossover for the 2380 and 2404 and compare to the active solution and see if the mini dsp is better for use in upper crossover point or the lower crossover point.

    One final point is l would use a 10 dB fixed pad or an L pad to attenuate the 2380 as at 110 dB sensitivity he is going to hear all the negative (noise and distortion) artifacts in the mini dsp and his signal path. I would also pad back the 2404 to match the 2380.

  4. #34
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    Hello everybody, and thanks for being super helpful

    I have been busy with couple of class-A amp builds, when I get those done I will start to fabricate some passive networks you guys have kindly presented here. My ultimate goal is to run this whole system as passive but bi-amped (class-D 200w to 2225, class-A single ended 25w to upper section) and get rid of miniDSP, but I guess that 2225 is not going to be huge problem to filter compared to upper section (?). L-pads are "must" for this reason too?

    If using miniDSP somewhere in this system gives great advantages, I can consider keeping it. But it's 2-channel only..

  5. #35
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    The variable L pad are initially a convenient way to match the balance of the drivers

    Measure the R valued of the Loads then use fixed R values.

    I l said use the mini DSP to try a few different approaches for the horn/ 2404.

    When you are happy take a screenshot of the response or preferably the voltage drive.
    The passive network can be then iteratively be optimised.

    I don’t think this is a difficult problem.

    But do NOT rely on frequency graphs alone as to the right choice.

    Trust your ears, not opinions.

  6. #36
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    Ok, I'm going to start by adding 2404H in to the system and everything else as active, 4 amp channels and 2-way active xo and dsp.
    Before I order anything;

    - 1,5uF cap series and 0.6mH air core coil paraller to 2404H

    - L-Pad for 2445J to match levels

    - DSP if needed

    (Also 47uF for 2445J as a protection and parallel resistor)

    Everything ok here? If it sound good, I just might stick to that and forget all-passive system

  7. #37
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    I was able to load the data files into Leap with the following results.

    The response is a good compromise with three elements c=4.7u r=4.7R r=12R

    I have also shown in another curve the inclusion of L=0.20mH in series with the network to attenuate the top end of the 2380.
    The network includes a passive high pass network to demonstrate effect of the mini dsp response overall.

    Similarly the 2404 network can be modified by reduced L from 0.6mH to l=0.24mH. The effect is faster attenuation below 7000 hertz.

    These types of series EQ circuits do however introduce some ripple in the passband due to the driver impedance modulating the voltage across the RC elements and the effect is some ripple in the response. My suggestion is use the Mini dsp for the crossover and 2380 EQ withe the passive curves as a guide.

    The RLC series Trap EQ networks JBL use in its K series of consumers systems are superior in this respect.

    In terms of parts I would buy both the 0.6mH and the 0.24mH to try.
    Attached Images Attached Images

  8. #38
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    Thanks alot guys I placed order for non-eq components to 2445 and 2404 at first, going to test that and I'll report results here as soon as I have tested it.

  9. #39
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    Ok, first listening session behind. 2404 adds some nice sparkle.
    Male vocals stays too "behind" and something wrong with 2225's dsp/xo settings: system sounds somewhat noisy with complicated music, but not articulate at all and there's no impact. Shame that can't do measurements while kids are at home, they make more noise than these speakers but I think that upper region works quite well now.

  10. #40
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    Now I had some time to eq 2225's, definitely much, much better! Maybe I get some amp with dsp possibilities to drive bass and keep class-A to horns. Thanks alot, you guys are awesome .

    Maybe some fine tuning later, now I want to enjoy music for awhile.

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