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Thread: Heil with a JBL Woofer part 2 Back wave attenuation for best in room balance.

  1. #16
    Administrator Robh3606's Avatar
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    Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.

    Rob
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  2. #17
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.
    I don’t think they behave the same way off axis as the horns do. It would be interesting to test.

    I have heard line arrays made with non-ESS AMT tweeters. I was very impressed.


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  3. #18
    Administrator Robh3606's Avatar
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    I don’t think they behave the same way off axis as the horns do. It would be interesting to test.

    I have heard line arrays made with non-ESS AMT tweeters. I was very impressed.
    Nice! Have never had the pleasure. No not exactly but take a look at these polars. Might open up bellow 4 K but overall pretty directional. The vertical is tight. Just with the stacks expect some lobbing depending on distance. The PDF is just a reference you won't know unless you measure.

    Rob
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    Vertical Response

    Here is the measured vertical response of the Heil AMT1 (ignore the SPL magnitude - these measurements were taken 1M from the AMT at 90db volume).

    Vertical response is good to 10K +/- 10 degrees, otherwise its collapses pretty quickly beyond 5.5Khz in the vertical plane.
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  5. #20
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    Quote Originally Posted by toddalin View Post
    Hence the wedgies in which we control these "mechanically" and through crossover component selection rather than through add-on electronic filtering.
    When you say mechanically do you mean the addition of compression and diffraction? The reduction in "throat" area may make for some increase in effective mass, and the triangle "wedgie" is a diffraction source beyond that, spreading into essentially two "mini horns" loading the "throat" rather than one diaphragm.

    "Add On" filtering is a bit of a misnomer if you are looking at active systems. Heils are inherently well behaved and thus XOs largely behave as-textbook, including notches/shaping, but active allows a whole 'nother degree of control that is more benign than the passive XOs. For heils, you want a very steep highpass if you want to cross them low, active does "steep" much better than passive. The waveguides I gave you provide a significant lift down to most reasonable XO points, which means you can electrically cross higher and/or less steep while not increasing diaphragm displacement or power input.

    RTA is great but if you can get some high resolution multi-axial data together, and distortion data, you'll be in a much better place to refine your design, 1/3 octave is what I'd initially used when working with Heils but higher resolution gives you much more insight. If you like what the wedgie's doing, you may try a semicircle profile appended to the outward side of it, to smooth diffraction from those hard edges near your high frequency device.

    The lateral on them can be treated as a horn, but note on the flat sections of the waveguides I provided that a top panel can also be applied- it makes limited difference- the heil, being tall, is already relatively directional in the vertical.

  6. #21
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    Quote Originally Posted by badman View Post
    When you say mechanically do you mean the addition of compression and diffraction? The reduction in "throat" area may make for some increase in effective mass, and the triangle "wedgie" is a diffraction source beyond that, spreading into essentially two "mini horns" loading the "throat" rather than one diaphragm.

    "Add On" filtering is a bit of a misnomer if you are looking at active systems. Heils are inherently well behaved and thus XOs largely behave as-textbook, including notches/shaping, but active allows a whole 'nother degree of control that is more benign than the passive XOs. For heils, you want a very steep highpass if you want to cross them low, active does "steep" much better than passive. The waveguides I gave you provide a significant lift down to most reasonable XO points, which means you can electrically cross higher and/or less steep while not increasing diaphragm displacement or power input.

    RTA is great but if you can get some high resolution multi-axial data together, and distortion data, you'll be in a much better place to refine your design, 1/3 octave is what I'd initially used when working with Heils but higher resolution gives you much more insight. If you like what the wedgie's doing, you may try a semicircle profile appended to the outward side of it, to smooth diffraction from those hard edges near your high frequency device.

    The lateral on them can be treated as a horn, but note on the flat sections of the waveguides I provided that a top panel can also be applied- it makes limited difference- the heil, being tall, is already relatively directional in the vertical.
    Good to hear from you Jeff.

    Yes, "mechanical" provides both compression and diffraction. My plots show an increased output of the lower frequencies through loading and a decrease at the peaks from diffraction, just as my slant plates do for the 2402, though probably not to the same extent. I would bet that like the slant plates, lateral dispersion is increased, especially for theose frequencies that were peaky.

    I do have two shapes of wedgies with one being a triangle, and the other "contoured" as you suggest. This was cut section at a time on the laser and the pieces stacked. The included plots are for the contoured version. The exact distance from the point to the diaphragm is critical and must be done with an RTA or similar to maximize its benefits. Too close and the highs are lost, and too far does not provide the desired effect.

    Because I cross them over at ~4kHz, the wavelengths are much shorter and cause less cancellation.

    Brass and acrylic, Phase 1:





    Clear acrylic triangle, Phase 2:





    Laser cut black acrylic stacked sections, Phase 3:









  7. #22
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    Quote Originally Posted by Robh3606 View Post
    Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.

    Rob
    There are four ways to stack these. They can be stacked vertically, horizontally/vertically, horizontally/horizontally (toed out as was done by Heil), or one can be turned 90 degrees. The difference?

    Know that Heil ran their "professional model" (AMT 6) with several of the AMTs set 90 degrees from their home offerings and toed out in an arc.



  8. #23
    Senior Member jmpsmash's Avatar
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    Quote Originally Posted by toddalin View Post
    Hence the wedgies in which we control these "mechanically" and through crossover component selection rather than through add-on electronic filtering.
    your wedgies piece looks great, but the understanding of how and why it works, is unfortunately a bit beyond my understanding of acoustics.

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    When I access my entertainment center to put in a disk/make an adjustment, I stand behind the left speaker, right infront of the back of the tweeter.

    When I change my Yamaha RX-Z9 into "CD Direct" mode that turns off all of the digital circuits and panel lights (essentially puts the Oppo 95 CD player directly through the volume control circuit to the two main channel power amps), the "hash" level goes way down and this is easily notable to my ears. And this should be a very subtle change.

    So I ask again, is the the AMT that is harsh, or is it just passing inherent harshness in the system along to the listener?

  10. #25
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    Quote Originally Posted by toddalin View Post
    So I ask again, is the the AMT that is harsh, or is it just passing inherent harshness in the system along to the listener?
    If the direct mode sounds vastly better you need a better solution than the yamaha. Heils are not at all inherently harsh once they've been smoothed out from a frequency response perspective.

  11. #26
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    Quote Originally Posted by badman View Post
    If the direct mode sounds vastly better you need a better solution than the yamaha. Heils are not at all inherently harsh once they've been smoothed out from a frequency response perspective.
    "Direct mode" is the solution to removing digital artifacts and noise through the receiver, but they still remain to some extent through other aspects of the system (conversion within the Oppo) and recording process, and the Heils let us hear them. Others who have complained of harshness may want to investigate other avenues to remove digital aspects/artifacts from their system and report back.

  12. #27
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    I've moved my speakers about and they are now closer to the back wall with one of the Heils now in front of a big mirror. The other one is sort of in front of a smaller picture.

    I was listening to the Doobie Bros a bit ago and thought a track was too bright. When I adjusted the L-pad, I had my ear beside the Heil and its reflection from the mirror creating a glare was unmistakable. These are also probably the frequencies that sound like they are "right at your ear" as described previously.

    I put the open cell foam behind them (but didn't replay the track) and will try some different foam types/placement.

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    Was listening to ELP Pictures at an Exhibition last night (original CD) and was hearing a distortion in the left channel that seemed to eminate from the Hammond, rather than the system. The Ethyl Mermans are very revealing. Maybe someone could listen for this and comment as to whether they also hear it?

  14. #29
    Administrator Robh3606's Avatar
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    Hello Toddalin

    Go checkout some tunes from The Nice. Pictures is quite long where Blues Variation?

    Rob
    "I could be arguing in my spare time"

  15. #30
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    Quote Originally Posted by Robh3606 View Post
    Hello Toddalin

    Go checkout some tunes from The Nice. Pictures is quite long where Blues Variation?

    Rob
    I believe so. I'll listen again in the near future and get a track#/time.

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