Free Response Graph and Mode Calc.

Discussion in 'Archived Threads 2001-2004' started by Chris Tsutsui, Sep 7, 2002.

  1. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    SPL Compensator and Graph
    Download the Excel Document HERE, (Microsoft Excel needed) [33kb]
    1. Explains how to use a Radio Shack SPL meter to record frequency response.
    2. Enter in numbers, view adjusted measurements and 3 different graphs.
    3. Enter in room dimensions and find out ALL standing waves for that room and what to do with them.
    Please let me know if I should revise it/make changes or any sugggestions. Soon I'll be building HH resonator bass traps and acoustic paneling so I might as well make a page that has plenty of pics & how to make them.
     
  2. Mark Fitzsimmons

    Mark Fitzsimmons Supporting Actor

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    Do you have tones available for use with your spreadsheet?
     
  3. Ned

    Ned Supporting Actor

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    Chris-
    Thanks for the spreadsheet. Do you think there is any value in having more data inbetween some of the octave spacing you used? Say you had peaks at 35 and 45hz, those might not be illustrated in the graph.
    Mark-
    http://www.nch.com.au/tonegen/
     
  4. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Good ideas, I have a bunch of tones and I do have a tone generator as well. Here's a link to some tones:
    http://www.snapbug.ws/sinewaves/
    Personally I like the tone generators because you can play around with overlapping tones and sweeps at different speeds.
    This was just a simple excel program I whipped up, since there's some interest in EQ, I'll spend some more time on it.
    Ned, I will have to add some more graphs with different "octave" type spacing. Reason I didn't include frequencies like 35 and 45 is because I don't have the adjustment numbers for them. The adjustments can easily be estimated though. If you had a peak at 45 you'd probably see a rise at 40 and 50 but it would be nice to see a more accurate "peak" in the hump.
    That would also probably make targeting bass traps/HH resonators more effective. I'll be building some soon and doing some experimenting to see exactly how effective they are and whether the measurements I've been taking actually mean anything. I'll keep posted as they are "DIY" acoustic panels and resonators.
     
  5. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Edit: feel free to edit the file. If you email it to me I can put it on my site and give credit.
    [email protected]
    Please let me know if there's a mistake in a formula or in information. I tried to keep the reading as simple as possible.
     
  6. Ned

    Ned Supporting Actor

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    I plugged my current (nasty) room measurements in and the predicted curve between points was fairly close.

    e.g My measurement at 58hz was 81db and the interpolated curve read 78db. The measurements on either side were lower but it was still close on that frequency which has my highest peak (+11db above the average level).
     
  7. TysonL

    TysonL Agent

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    I assume you guys playing your tones though a PC fed to your per/pro?

    Tyson
     
  8. Jack Gilvey

    Jack Gilvey Producer

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  9. Ned

    Ned Supporting Actor

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    I made my own CD with the NCH tonegen.

    Tracks 1-9 are various sweeps and track 10 is 10hz, then each following track corresponds to frequency (track 43 is 43hz) up to 99hz.
     
  10. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    This week I'm gonna be testing response with overlapped tones. Such as playing 40 + 80 at the same time and then incrementing those 2 tones up.

    I'm gonna do some measurements and see how the response is. Theoretically, shouldn't the 2 tones overlapped play at the same volume as another 2 tones overlapped?

    I came across the idea after overlapping deep sine waves to produce LOUD bass notes for my car's sub.

    Has anyone done this or have any ideas if it would be a more accurate way of testing frequency response than single isolated tones? Isn't music essentially multiple overlapped tones?
     
  11. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Just thought I'd mention how crucial these room modes are with a +/- 9db at the center of the room. (ouch)
    Ok, theoretically for my room there should be a null 4 feet from the ground @ 71hz. (The big ole first order floor/ceiling axial room mode)
    I just took measurements from listening position at the following different heights:
    Height (Lineal ft) SPL (slow C, @ 71hz)
    0 ft ---------------- 90 DB
    1 ft ---------------- 89 DB
    2 ft ---------------- 87 DB
    3 ft ---------------- 78 DB
    4 ft ---------------- 72 DB
    5 ft ---------------- 79 DB
    6 ft ---------------- 82 DB
    7 ft ---------------- 84 DB
    8 ft ---------------- 87 DB
    EDIT: I also updated the Response Graph and Mode Calc. and added 2 new features:
    1. Find out how loud your subwoofer plays from a specified distance, just type in the sensitivity and the watts.
    2. Find out how much louder your bass would be from the listening position if you added a second sub or upgraded the amplifier.
    3. Find out how close your sub gets to THX levels with the "Peak" calculator.
    Same link HERE to download file.
     

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