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Thread: Just a thought

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    Just a thought

    Is it possible to bypass beaming issues with large drivers by simply flipping them around in the baffle? For example a 2245 flipped around and mated to a 2441 and 2405. I'm obviously assuming driver geometry is responsible for the beaming.

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by gasfan View Post
    Is it possible to bypass beaming issues with large drivers by simply flipping them around in the baffle? For example a 2245 flipped around and mated to a 2441 and 2405. I'm obviously assuming driver geometry is responsible for the beaming.
    No, it's a function of frequency and sound wave length.
    David F
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    Quote Originally Posted by DavidF View Post
    No, it's a function of frequency and sound wave length.
    From what I've gathered, beaming begins when the wavelength reaches the diameter of the radiating cone. But it seems off-axis dispersion can be mitigated or compensated for simply by changing the angle of the radiator. Why would this not work?

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    Administrator Mr. Widget's Avatar
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    Take a look at typical driver polar plots, that might help answer your question.


    Widget

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by gasfan View Post
    From what I've gathered, beaming begins when the wavelength reaches the diameter of the radiating cone. But it seems off-axis dispersion can be mitigated or compensated for simply by changing the angle of the radiator. Why would this not work?
    I think I misread the question. You are asking about the dispersion characteristics of a particular driver within a set bandwidth. I can't comment on the theory involved but practically speaking you will introduce phase/combing issues with reflections as you move up into the midrange, just where the dispersion of the large cone starts to narrow significantly.
    David F
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    Quote Originally Posted by DavidF View Post
    I think I misread the question. You are asking about the dispersion characteristics of a particular driver within a set bandwidth. I can't comment on the theory involved but practically speaking you will introduce phase/combing issues with reflections as you move up into the midrange, just where the dispersion of the large cone starts to narrow significantly.
    Yeah, I get that but I'm suggesting the reversal of the cone would cancel that effect just by the same way it's caused. It seems the angle of dispersion should be seriously widened when the cone is reversed?

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    Senior Member Ian Mackenzie's Avatar
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    Yes and no

    As frequency goes up only the centre of the cone radiates to the point where only the dust cap radiates as l recall

    In theory if you reversed the cone then the response may not go as high?

    That depending on the circumstances might be a good thing or a bad thing

    Generally a straight 15 inch ribbed cone will enter cone break up between 1-2 khertz or less depending on the cone construction. An 18 inch woofer lower like 500 hertz. Itís an indication it will start to sound shithouse above the cone breakup frequency.

    A 15 inch curvilinear cone will enter cone break up in a more controlled manner and be usable to 2-3 khertz

    As a general rule a 15 driver has approximately 100 degree dispersion at 1000 hertz

    At this point itís assumed the response will be -6 dB down at that off axis frequency in comparison to the on axis frequency.

    You can tilt the driver but on the other angle the off axis response will be even lower

    I hope that helps clarify your question

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    Senior Member Ian Mackenzie's Avatar
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    If your horn is big enough like an OMA horn that can go down to 300 hertz you might win.

    But finding a driver and horn to do that well is both big and really expensive

    Some people who are a wiz (sorry) with horns can design a horn to solve your issue

    See John Inlows horn page.

    http://www.inlowsound.com

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    Understandable YouTube Clip about Wave Motion

    Quote Originally Posted by gasfan View Post
    Is it possible to bypass beaming issues with large drivers by simply flipping them around in the baffle? For example a 2245 flipped around and mated to a 2441 and 2405. I'm obviously assuming driver geometry is responsible for the beaming.
    Look for YouTube Clips named "Exploring wave Motion". There is a sequence of 5 Clips belonging to each other. What you need to understand is the diffraction of water waves and the Huygens principle. Stay away from articles and clips exploring optical waves, as they tend to become quite complicated at the end (Quantum theory). What you learn about water waves can easily be applied to acoustical waves.

    ruediger

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    Quote Originally Posted by Ruediger View Post
    Look for YouTube Clips named "Exploring wave Motion". There is a sequence of 5 Clips belonging to each other. What you need to understand is the diffraction of water waves and the Huygens principle. Stay away from articles and clips exploring optical waves, as they tend to become quite complicated at the end (Quantum theory). What you learn about water waves can easily be applied to acoustical waves.

    ruediger
    I did watch a few of these. Not sure which might apply to the motion of a cone, though. Diffraction of water through an aperture clearly demonstrates beaming. Otoh reflection off of a convex plane shows what I've suggested perfectly while reflection off of a concave plane shows beaming again. Since the cone of a speaker is the source of the wave, I have no idea how to predict the outcome using those video examples. It seems the examples of reflection would most logically apply, apparently confirming my initial suspicion?

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