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Thread: Inexpensive wavguide for 1" drivers

  1. #1
    ralphs99
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    Inexpensive wavguide for 1" drivers

    On the tail of the excellent work published by Zilch and others, I've been testing a cheapo waveguide that might be of interest.

    MCM sell a $10 circular 6.5" waveguide that fits on 1" screw mount compression drivers. Part number 54-580. http://www.mcminone.com/product.asp?...%5Fid=54%2D580

    It works very well with a nominal directivity of 90 degrees circular.
    Cut-off frequency is about 1.5kHz and it starts to lose direction control below about 2.5kHz although still useable down to a least 2kHz. Could be a good option for something like a 2407 driver.

    Note that some rough EQ has been added to the on axis response to make it easier to see the what's happening.

    Cheers,
    Ralph.
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  2. #2
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    There are similar devices on Parts Express.

    Ian

  3. #3
    RIP 2011 Zilch's Avatar
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    I'm always a little confused when doing similar testing.

    The specs are usually "included" angle, i.e., "90°" being +/- 45° from axis.

    Is your 45° "off-axis" or included angle?

    Nice measurements, in any case.

  4. #4
    ralphs99
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    Hi Zilch,


    My plots show the degrees off axis, so the 45 degree plot has an included angle of 90 degrees.

    Cheers,
    Ralph

  5. #5
    Senior Member GordonW's Avatar
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    What's the "rough EQ" entail? Top end lift? Could you post a curve of on-axis without the EQ?

    Looks like a pretty "linear" curve, though. No real discontinuities. Very good performance, from that standpoint...

    Regards,
    Gordon.

  6. #6
    RIP 2011 Zilch's Avatar
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    Let's try and guess the driver Ralph used from the curve.

    Not a 2407, apparently.

    Zilch guesses 2416 or 2426.

    Only one? 2426, then....

  7. #7
    ralphs99
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    Zilch is right on the money. 2426 with the snout removed.

    I can't offer a plot of the driver plus waveguide before EQ.

    The purpose of the tests were just to get an idea of the off-axis response of the wave guide. I wasn't too worried about the actual frequency response, just how it changed as I measured at increasing angles.

    But I can give you the EQ settings I used with my driverack:

    MCM waveguide on 2426 with baffle approximately 270mm x 500mm.
    Equalised for flat on axis. Measurement distance= 0.5m, 1/24th smooth.
    EQ: HP Shelf 5.6kHz, 10.5dB, S=9; 2.12kHz, 6dB, Q=1.57;
    3.15kHz=-3.5dB, 4kHz= +3.5dB, 5kHz= -1dB, from here just tried to add HF boost as the HF Shelf ran out of gain, 10kHz= +0.5dB, 12.5kHz= +2.5dB, 16kHz= +6dB.

    From my notes it says I ran out of parametric HF EQ and so I just boosted a bunch of frequencies in the top octave with the graphic. Hence the response is a bit rougher than could be achieved with more parametric bands.

    Below is the on axis response on its own:
    Attached Images Attached Images  

  8. #8
    ralphs99
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    The response isn't as smooth as the first plot I posted 'cause it doesn't have as much smoothing, 1/24th octave vs 1/6th octave.

    Here is the original set of plots with the same 1/24th octave smoothing applied.

    Cheers,
    Ralph
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