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Thread: Passive Monitor Thread

  1. #31
    Senior Member pos's Avatar
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    Something interesting is that to obtain the same 36dB/oct LR acoustical target the 476Mg requires a 18dB/oct electrical filter, whereas the D2430K requires a 6dB/oct electrical filter.
    That tells a lot on the difference in the capabilities of these two drivers in the lower part of there range...

  2. #32
    Senior Member pos's Avatar
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    476Mg vs D2430K voltage drive for the same 800Hz 36dB/oct Linkwitz-Riley acoustical target

    Name:  476Mg vs D2430K voltage drive.jpg
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  3. #33
    Senior Member pos's Avatar
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    Rob, could the 1.6kHz and 3.2kHz notch also be done in the passive filter?
    It looks like the 476Mg would also benefit of these, together with a broad and gentle boost in the 2k-5k range

    There appear to be a periodic pattern here: 800Hz, 1600Hz, 3200Hz...


  4. #34
    Administrator Robh3606's Avatar
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    Hello Pos
    476Mg vs D2430K voltage drive for the same 800Hz 36dB/oct Linkwitz-Riley acoustical target
    That is the electrical only does not include the 6db for the protection capacitor or the roll off of the driver on the waveguide. Rob
    "I could be arguing in my spare time"

  5. #35
    Administrator Robh3606's Avatar
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    Hello Pos
    Rob, could the 1.6kHz and 3.2kHz notch also be done in the passive filter?
    It looks like the 476Mg would also benefit of these, together with a broad and gentle boost in the 2k-5k range

    There appear to be a periodic pattern here: 800Hz, 1600Hz, 3200Hz...
    Don't put too much stock in these measurements up front. I really need to do these outdoors. I just got the new CLIO Pocket system for laptop. You would need high Q filters to take the 1.6 and 3.2 out. At this point I am trying to best fit the curve and even worst case I am about 2db out Rob
    "I could be arguing in my spare time"

  6. #36
    Senior Member Don C's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Has anyone measure a 2452 on this waveguide?
    In my "Experiments with M2 horns" thread I'm using 2452s, with coated 16 ohm diaphragms. I like the sound so much that I still haven't bothered to put the Be diaphragms in yet. Hopefully things will slow down a bit at work and I'll find time to try those soon.

  7. #37
    Senior Member pos's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Hello Pos That is the electrical only does not include the 6db for the protection capacitor or the roll off of the driver on the waveguide. Rob
    According to yours and JBL's measurements, both voltage curves should show the same thing, and make their respective driver reach the LR 36dB/oct target within a few dBs.

    I included the protection cap in the M2 voltage curve (1st order at 209Hz)

  8. #38
    Administrator Robh3606's Avatar
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    Hello Pos

    Oh I got you now.

    So what are you thinking?? The 476 has more output down on the low range??

    Rob
    "I could be arguing in my spare time"

  9. #39
    Senior Member pos's Avatar
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    Yes it looks like it has much more output, which is a really good thing.
    But on the other hand it is difficult to get accurate measurements in the stop band with a horn as so much parameters come into play (distance, reflexions, gating, etc.)

  10. #40
    Administrator Robh3606's Avatar
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    Just bringing this back to life. Starting to cut wood on the cabinets wondering how some of you have used your 2216nd's. I am going passive and not trying to clone the M2. Same with the cabinet I am building a ported woofer cabinet and a separate upper cabinet for the M2 waveguide and 476Mg.

    Using 2" quarter rounds on the bass and upper horn cabinet to lower diffraction of the bass cabinet and to "round over" the waveguide. The wavequide actually fits very well into the 3/4 grove in the rounds. The horn is 7/8 thick at the edge so the round will give a smoother termination than the abrupt edge of the waveguide.

    I am looking at 4.7 cubic ft tuned to either 26Hz or 32Hz. I am liking the 26Hz tuning as I can easily just add a bit of EQ @ 25Hz to bring up the low bass level in the room. The sim is 6dB same as a B380 and you end up with a relatively flat and extended low end. If you try to EQ the 32Hz box you get a peaked response which I definitely do not want.

    Rob
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  11. #41
    Senior Member Ian Mackenzie's Avatar
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    Hi Rob,

    Interesting. My 2216 woofers are yet too be put to work.

  12. #42
    Administrator Robh3606's Avatar
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    This is how the round overs work with the waveguides. Not bad it's not flush but the proud portion of the waveguide I don't see as an issue. Working on the bass cabinets over the weekend with all the panels cut. Time to glue and screw!
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  13. #43
    Senior Member grumpy's Avatar
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    Looking good Rob!


  14. #44
    Administrator Robh3606's Avatar
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    Happy Easter!

    Today I finally get to put my cabinets together. A heads up on proper storage of the 2" round overs I am using. I left mine in the shipping container and never opened them. That ended up being a big mistake. When they shipped them they tightly shrink wrapped the ends and it bowed the 4 I had ordered. So needless to say after a couple of years in storage them are set that way.

    Still OK but not without some work. Usually they are completely straight and you can easily use the the glue to temporarily hold everything in place until you get straps on. Not now with the bow. The straps will pull them straight and flush but I had to build a jig so I could get the side panels together so I had a rigid box to get the straps onto without the whole thing falling apart. Had plenty of scraps so I built a fixture to hold the side panels in place to glue and screw cross braces in place while keeping everything properly aligned and square.

    Now with that done I can get things going on them.

    Rob
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  15. #45
    Administrator Robh3606's Avatar
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    Got one strapped up with the glue drying. Took every bit of tension in those straps to get those quarter rounds to flatten out and be flush with the front and side panels.

    Rob
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