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Thread: Fixed L-Pads

  1. #166
    Member dmtp's Avatar
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    - FWIW, many horns that have large aspect ratio mouths ( in comparison ) to the H91 , show a reduction of those impedance ripples ( or impedance reflections ). It's worth looking at Widgets' impedance plots of his H4003 (?) horn clones ( I think that plot is posted in the public forums ) .
    Yes, I suspected that was the problem with the H91 - the mouth is too small to support 500 Hz. One of the nice things about a tractrix horn is that it has a defined mouth that cannot be exceeded whereas an exponential horn can be extended to any size mouth and is still expanding.
    - FWIW ; I use a round mouthed exponential horn on a Altec 288-8K ( that supports 800 hz fairly well ). The horns rising Directivity Index ( DI factor ) means I need to use a series LCR ( strapped across the driver ) to flatten a quite symetrical peak ( centered around 6200 hz ) . I also use a pretty simple HF bypass circuit that does ( somewhat ) overdo the HF content ( and therefore, "contaminates" the octave below /as you have run into / & forces the need for a bigger notch )
    The directivity issue is the main reason I decided to "finish" the project before finalizing the XO. These speakers will be firing 'into' a curved reflector panel ala paragon/metrogon. This will obviously help dispersion, but I may be more concerned with power response than on axis response and may need to leave in a fair amount of on axis HF rise to get good HF response in the listening area. I now know how to 'get' and how to 'tame' the HF response with quite a lot of options.
    Thanks to everyone - especially Zilch and EarlK - for all the help. When I finally get things finished, I will post picutres and response curves. In the meantime, I may come back to the well for help as things progress.
    Again, thanks to all!
    MarkT

  2. #167
    Member dmtp's Avatar
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    Results!

    OK, so it has been a long time, but the speaker is finally together and in the den. Yes, an HD TV on the wall will be an improvement as will finishing the grill covers, but I thought you might like to see the results of my efforts. Immediately following this, I will post the sonic results!
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    MarkT

  3. #168
    Member dmtp's Avatar
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    For those more interested in the sound than the looks, here are my final plots. Note that these are taken with the mike placed right at the cneter of the curved front touching the front. There is no way to eliminate room effect, so I adjusted the "midrange" L-pad by ear. It is set @ -2dB which is about what these curves look like to me. Any higher and it sounds too bright. As is, they are GREAT!
    FWIW, the 500 Hz dip must be a room effect or measruing artifact. I was worried it was a crossover notch, but I tried reversing the leads of the LE85 and it created a deeper notch soemwhat higher in freq. When measured half way between the center curve and the speaker itself, there was a deep notch @ 200 Hz. Perhaps this summer I'll take the assembly apart and measure one of the speakers out doors, but for now, I'm happy listening.
    Thanks to everyone for all the help, this truly was a "community" project!
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    MarkT

  4. #169
    RIP 2011 Zilch's Avatar
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    That looks mighty fine, I must say!

  5. #170
    Senior Member timc's Avatar
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    Very nice work. Hope it sounds as good as it looks




    -Tim
    2213 + 2435HPL w/aquaplas + H9800 (Matsj edition)

  6. #171
    Senior Member Skywave-Rider's Avatar
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    Wow, it's beautiful! Would love to hear the imaging on that. Recently read about the Paragon.

  7. #172
    Senior Member spwal's Avatar
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    reading is one thing, hearing one is quite another!

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