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Thread: Quick & Dirty 4430-Inspired Two-Ways Part II

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  1. #1
    RIP 2011 Zilch's Avatar
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    Quick & Dirty 4430-Inspired Two-Ways Part II

    Continued from Quick & Dirty 4430-Inspired Two-Ways Part I

    Giskard:

    1) 1.7 uF, 0.6 mH
    2) 2.15 uF, 0.6 mH
    3) Full Range

    Boosted everything about 3 dB, no frequency shift. (SOUNDS good tho....)

    I assumed you meant stay with original inductor value, not Guido's suggested 1.0 mH?
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    Quote Originally Posted by Zilch
    Boosted everything about 3 dB, no frequency shift. (SOUNDS good tho....)
    Ok... should have been ~ 1.7 dB but whatever. How are you on coil values? Can you go in increments of 1/100 mH? With the 2.15 uF you have change the inductor to 0.76 mH. That should give you a 4 dB increase at 1 kHz and a 2 dB increase overall in the high pass.

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    Quote Originally Posted by Giskard
    How are you on coil values? Can you go in increments of 1/100 mH?
    I have four Jantzen 20 Ga 1.0 mH coils, and a B&K LCR meter that reads to 0.01 mH, yes. WT2 confirms the readings are correct, as required.

    I'll unwind one to 0.76 mH and try it. I can also crank the RTA resolution up to 2.5 dB per major division, now that we're close. Can you illustrate graphically what's going on with this portion of the circuit for us please? I'm surprised the values require this level of precision.

    I should invest in a filter simulator myself, probably. One thing this thread has made abundantly clear to me is that it's about the crossovers as much as the drivers, and, surprisingly, within fairly broad limits, the boxes themselves are the least of getting it all to work together....

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    Yeah, I can post what's going on with the voltage drive in awhile. Let me know how the 0.76 mH works first. Post the bb6p file for the horn/cd combo complete with Q, fs, etc. I'll also need an impedance curve from 500 Hz on up.

    "One thing this thread has made abundantly clear to me is that it's about the crossovers as much as the drivers"

    We've talked about this at length before. Back in the day when JBL was cranking out such stellar circuits as the N100, other companies were taking junk drivers and making them sound listenable with proper application of filter design theory.

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    Perspective:

    Bigger than a breadbox, but decidedly smaller than L200 (rear baffles aligned here), Z1 has good WAF potential; no matter the viewing angle, you can never see all of the sides at once, thus masking its real volume. Trompe l'oeil confers delicious asymmetry (think L250,) in all but direct head-on view.

    In comparison to real 4430, note that it's the same width (22") and 1" deeper at the base (ignoring 4430 horn, which sticks out an additional 3-1/4"). No matter, the difference in perceived mass is apparent.

    O.K., standing-wave and reflections gurus, does this design really (or theoretically, even) SUCK?

    [Excuse the clutter, please. I DO have a life here.... ]
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    My personal preference would be to follow the front trapezoidal shape all the way front to back...

    John

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    A little more explanation:

    For many, the brain glazes over at the sight of response curves and crossover schematics. Perhaps this little bit more information will help clear the hyper-technical fog over this:

    To make the HF driver "play" with the woofer, we could power them each from a separate amp (biamp) and apply the requisite boost in the high frequencies to level out the HF response using active equalization. We'd rather just hook them both to the same amp and have them work right together, tho, and that means use a passive filter crossover network. 4430 does it separately for mid- and high-frequencies; we're doing it "all-in-one" here.

    Since passive networks don't add any power to the system, we can't boost anything, only cut. Fortunately, HF compression drivers such as the 2431H we're using here are WAY more efficient than the woofers we're mating them with. 2235H has a sensitivity of 93 dB, for example, and 2431H is up around 110 dB (actual spec unknown).

    Thus, we have something like 17 dB of excess SPL available in the HF driver to do the requisite deed when driving both woofer and HF driver from the same amp souirce. All we have to do is progressively attenuate the power delivered to the 2431H from 20 kHz downward to match the SPL of the woofer at the crossover point (1 kHz, in this case). The inverse of the driver response curve above tells us, generally, what the crossover must do to accomplish this, such that the end result is a seemless flat response throughout the range of interest.

    The crossover voltage drive curve (top graph) is what we're using to do it. We try to adjust the values of the components in the filter to "shape" the curve (the resultant attenuation varying with frequency) to make the HF driver perform as desired. You can see we have essentially 0 dB attenuation at 20 kHz, there. Response at all frequencies below that is cut by varying degrees, as required, to yield flat output.

    The result is shown in the combined response curve (bottom graph), where we measured the actual performance of crossover, driver, and horn playing together. Looking at the various curves, we only use up ~13.5 to 15 dB of the available 17 dB HF driver "headroom" to do it here. That's a good thing; if much more were required, we'd run out of SPL and end up giving up response somewhere.

    Well, that's the "Quick and Dirty" synthesis of what's going on with this: Graph A + Graph B = Graph C = sounds GOOD!! Hope that helps.

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    Well explained! It's good for our not THAT experienced members.

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    Quote Originally Posted by Guido
    It's good for our not THAT experienced members.
    Yeah, that'd be ME!

    It's only my second pass down this path....


    Infredible was just here with his stack of astounding test disks puttin' the Q&D's through their paces. I'm pleased to report that no apparent damage occurred to the either the house or workshop. Gonna take a day or two for me to decompress....

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    Senior Member Guido's Avatar
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    Quote Originally Posted by Zilch
    Infredible was just here with his stack of astounding test disks ....
    Which one, which one

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    Peggy Lee, Dave Crusin "Migration" (see thread "What's playing now"), Andreas Vollenweider....

    Infredible's complete test kit is proprietary, of course; the ride'll make yer nose bleed.

    Johnaec brought lotsa Little Feat, others, mostly new to me, expanding horizons here.

    Mr. Widget has some good ones I gotta get, too....

    It's great fun when forum members bring their favorites to try. You get to hear lotsa different stuff you wouldn't normally hear on your system, and you can turn them on to your own arcane "specialties" at the same time.

    Mine? Presently "Red Hot & Blue" Cole Porter compilation, Chico Science (Brazilian), "Amused to Death" (a reminder not to mix politics and rhythm), "Up" (which I don't understand), Brian Ferry "Frantic," and an array of Pink Floyd, of course.

    Back to regular programming AFTER this brief musical interlude....

    ["Soon be oh vah, soon be oh vah...."]

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    Quote Originally Posted by B&KMan
    What is ( y ) scale please ??? 1.5 or 15 DB...
    That's 15 dB. You can see the corrections at the cursor for 6k3 Hz of -4.0 and -5.5 dB, respectively.
    Quote Originally Posted by B&KMan
    mmmmm titanium sound sweet ???
    good news....
    No, no. LE85 is vintage aluminum. See the title of the post. LE85 = 2420.
    Quote Originally Posted by B&KMan
    but diaphrams it is completely news or reclycling used ???
    Diaphragms are original. The red wax seals are intact on these.
    Quote Originally Posted by B&KMan
    it is possible to explain little bit more what is ultra curve pro works ???
    Behringer UltraCurve Pro 24/96, an inexpensive (>$300) combination RTA and digital equalizer, including an "Auto-equalization" function which will listen to the speakers and adjust the 1/3 octave equalization bands to make them play whatever response curve is specified.

    UltraCurve is often ridiculed by the pros as a cheap knock-off of better tecnology, but there's a furtive underground cult here using them routinely.

    Me, I use it for research....

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    Up from the dungeon, 4507 "Utility" enclosures come with 2226H installed as 4647A. With 1" thick MDF front baffle and cross-braced with 2x4's (see pic), they're about the same size as L200, but with more internal volume (5 cuft.) as the front baffle is only recessed 1/2" and not sloped.

    Closing two of the four 2-7/8" dia. X 6-1/4" ports in each will retune them from 40 Hz to 28 Hz. Closing just one in each will bring them to 4430 standard 34 Hz tuning. They'll be getting 2235H's installed, and maybe PT waveguides or 2342's cut in (inverted). 2344A's won't fit in the baffle; there's only 11-1/4" below the woofer cutout there. Everest horns are merely for "illustration."

    Ref: http://audioheritage.org/vbulletin/s...ead.php?t=7480

    Compare to the current version Citation 7.4-based Mini-Everests, middle.

    [Dwarfdom. ]

    Available unassisted 2235H bass tuning options, bottom. Two ports open = blue, three open = red, and four open = black. There's unexploited versatility in these humble boxes....
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    Senior Member DavidF's Avatar
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    Zilch, there is an old Laurel & Hardy short film where the boys go to sea to get Hardy away from the job. It seems the ole boy goes into a rage whenever he hears a horn. A condition prompted by his constant immersion in sound at his job in a horn factory. Hmmm...

    DavidF

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