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  1. #1

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    Default First time with REW

    I have my mic arriving today, I have browsed over at the HTS forums but wanted some input here. Given the nature of SDA's, do I perform this ith the IC connected? Also, since there are many different displays and graphs with REW, which one is better suited for measuring room acoustics or what have you used with success?

    Just getting my ducks in a row ahead of time.

    Thanks. Any advice is appreciated.

  2. #2

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    Use the IC cable, that way it's measuring what you hear normally.

    I prefer the waterfall graph the most.
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    I would measure both ways and then you can see how things are working.
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    Some feel the Interconnect Cable should be disconnected for any HT Measurements or Calibrations. I disagree. Remember, below 150 Hz, the dimensional and stereo drivers are working in unison. If you disconnect the cable, you'll be halving the low bass frequencies (in a 2 driver configuration), and worse, the dimensional woofer will act as another passive radiator. The end result is a poorly tuned system, that won't even allow the stereo woofer(s) to perform properly.
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    Name:  Test1..jpg
Views: 123
Size:  35.3 KBHere's the first test, this is at 1/12 smoothing, first reflection foam is removed. The foam is only excess pieces of 3'x32"x2" packing foam and I believe is open-cell.
    Last edited by gmcman; 11-16-2013 at 07:41 PM.

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    Here's a better comparison, I believe the panel needs to be of a different material. Not something that's there normally, just wanted to try it.
    Attached Images  

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    So I went into the preamp settings and raised the 180Hz 1db, now the graph dipped so I'm concerned about the settings. I have the mic input inverted but the dropoff above 12kHz shows a normal graph so it should be fine.

    Interesting.

    The yellow graph is with the 180Hz raised 1db. Granted the graph is all over the place but I wonder why it shows a dip.
    Attached Images  

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    Something is not right, I just ran the test again through my headphones to confirm L & R output and the graph is almost the exact same, with nothing attached to the mic input.

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    I ran more tests, mic is working and REW is using it's data. I zoomed out slightly and tweaked more settings in the pre and here's what I have. Anyone who want's specific graphs let me know, not sure if this one tells much but this is where I'm at.
    Attached Images  

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    I just tried REW for the first time as well (yesterday) and didn't even get graphs this good/clean. I used an SPL meter as my mic, but I suspect my sound card isn't up to the task. Seeing as you had very little difference with/without acoustic treatments (are those corner panels?), I'm beginning to wonder if I'm wasting my time; after all, my setup (basic rectangular room) sounds good to me!
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    Quote Originally Posted by StantonZ View Post
    I just tried REW for the first time as well (yesterday) and didn't even get graphs this good/clean. I used an SPL meter as my mic, but I suspect my sound card isn't up to the task. Seeing as you had very little difference with/without acoustic treatments (are those corner panels?), I'm beginning to wonder if I'm wasting my time; after all, my setup (basic rectangular room) sounds good to me!
    When I get back home i will post more on this but I almost 100% certain you cannot use a SPL metet as a mic, you need a calibrated mic.

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    pGetting this thing tweaked a little more and this is with smoothing at 1/3. No panels in place but this room is fairly padded down with carpet and furniture. Looking at the waterfall shows about 240-300 ms time for RT/60... if I am reading it correctly.
    Attached Thumbnails Attached Thumbnails Click image for larger version

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  13. #13

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    Quote Originally Posted by gmcman View Post
    When I get back home i will post more on this but I almost 100% certain you cannot use a SPL metet as a mic, you need a calibrated mic.
    You can use SPL meter as mic. Just make sure to get a meter that has output option that you can pipe it back into your sound card for REW to use. From everything that I have read it is critical to get a sound card that has line in option. By default most of the built in sound card only support mic in.

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    Quote Originally Posted by shadowlight View Post
    You can use SPL meter as mic. Just make sure to get a meter that has output option that you can pipe it back into your sound card for REW to use. From everything that I have read it is critical to get a sound card that has line in option. By default most of the built in sound card only support mic in.
    Ok, I wasn't sure but thought it had to be a mic.

    Makes me want to try a cheap soundard that's adequate for REW just to compare. Only issue I have is now I am using a USB microphone and I cannot find any external soundcards that support a USB input for a USB external card, only RCA or XLR input to card.


    On a side note, here's another few tests at 1/3 smoothing. The red line shows speakers as they sit about 5" in front of my display, the gold line shows them moved 1" back, the blue line shows them moved 2" back from that and the high's no longer have a spike and are rolled off. Definitely shows what incremental speaker movements will do.

    Still have a big dip at 170Hz though.
    Attached Images  

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    Could that dip be related to room size? I was pointed to the following calculator http://realtraps.com/modecalc.htm at one point to identify if the issue was room related or not. I have not used it yet.

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    Here is a link to REW that I ran across, don't know if it will help but here it is.

    http://www.avsforum.com/t/1449924/si...terpret-graphs
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  17. #17

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    Quote Originally Posted by zane77 View Post
    Here is a link to REW that I ran across, don't know if it will help but here it is.

    http://www.avsforum.com/t/1449924/si...terpret-graphs
    Thanks, that's a great article...definitely answers a lot of questions in the first couple pages.

  18. #18

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    Yes, thanks for that link. I actually think a RS SPL meter (the same one many of us use to set speaker levels) makes a very good mic, but I think the problem (at least in my case) is the "cheap" sound card (no line in) on laptops. Even so, I get a curve I'm trying to interpret.
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