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Anyone have a user's guide for setting a sub's EQ?

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  • Anyone have a user's guide for setting a sub's EQ?

    Not the phase, gain, or crossover. I know how to do that, but I've never had a sub with an amp that had EQ features. I'd like to read the proper way to set one up if I ever get one.

  • #2
    Originally posted by SteveSatch
    Not the phase, gain, or crossover. I know how to do that, but I've never had a sub with an amp that had EQ features. I'd like to read the proper way to set one up if I ever get one.
    I'm with you. I have no idea on what to adjust after I run the test tones.

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    • #3
      My basic understanding is that the PEQ allows you to select:
      - a FREQ (frequency) that you want to adjust;
      - the BANDWIDTH (that is, the range above and below the chosen frequency) to which you want the adjustment applied (smaller # is a wider range; higher # is a narrower range); and
      - the LEVEL of boost or cut you wish to apply.

      Without some sort of room EQ software (REW or Omnimic), I think this amounts to a lot of guesswork. Which is why I won't tamper with the flat EQ settings until the next time F1Nels hits town with his Omnimic (which will allow me to see which frequency I need to focus on, what bandwidth I need and how much level is actually necessary to flatten things out).

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      • #4
        I'm with both of you guys, but I might be half a step ahead. SO in the interest of having my own thoughts reviewed by someone who knows better, and giving it to you guys in a novices perspective, I'll lay it out as I see it.

        The EQ built in to the amp is, as I understand it, single band (band pass) parametric. Here's the wikipedia article that can help with some definition of terms. That means it can enhance or diminish the signal it amplifies through one range (band) - the rest of the signal will remain unchanged. The band is defined by two parameters - the frequency and the bandwidth. The frequency you select is the geometric center of the band you want to change (usually diminish) and the bandwidth (Q) is the number of octaves over which the adjustment will be applied (I think this might be wrong). The last variable is the strength of the adjustment (at a maximum, as I believe the adjustment should roll of towards zero adjustment at the outer limits ("edges") of the band you select) measured in decibels.

        The complication comes from the logarithmic relationship between frequency and pitch. When you select frequncy, it is the geometric center of the band - that's different from the normal arithmetic center, so it cannot be calculated as the average of the high and low frequencies you want to define as the band. I have seen the math, and I have since lost track of it. For introductory purposes, I think it's adequate to just start guessing for Q, once you have a basic understanding of the terms I just defined. The math involves a golden ratio (Phi) which is something like half the the quantity one plus square root of five... it doesn't matter at this point. Also, be clear in your head that an octave is doubling of frequency, and is relative. (An octave up from 20 is 40, but one octave down is 10.)

        I was going to lead myself through an example to try and figure out the math, but I've failed. So I'll give you a link I found, and we can start fiddling. http://mobile.jlaudio.com/support_pages.php?page_id=144 - notice that the animation here only allows boost, which I think in general is not the way HT "should" be done.

        Fred
        P.S. As a note to tooskinny, in your other thread I suggested you try a higher Q, like .7 or .8 - I think I lower number might be better - it was backwards in my head a few minutes ago.

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        • #5
          I'm also looking for a easy to use free program for graphing my room response. I have Onix Graph Paper but no one seems to use that so I'd rather post in a format people are familiar with : )

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          • #6
            Maybe it would help if I knew what I was trying to achieve. From what I gathered you want the graph to be flat. Which point should that start and end?

            Hopefulfred I didn't try those settings yet. I will try the lower and see what happens.

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            • #7
              Originally posted by tooskinny
              Maybe it would help if I knew what I was trying to achieve. From what I gathered you want the graph to be flat. Which point should that start and end?
              You'll have to graph the response and make a judgement call. The flatter the better, (at least in general - there is some discussion about flat not always being right - read Wayne Pflughaupt's thoughts on the matter at HTS, links from this sticky in the REW forum) but with only one band PEQ, the room will still dominate the response. That's why I'd suggest room treatments (bass traps) before finalizing any EQ settings. At least, acknowledge that the EQ settings will likely change if treatments are introduced.

              You can trust that in a room without walls (where the reverb would never change the overall response you hear) a sub like the ones Craig sells will be pretty darn flat. Most rooms will resonate at one or two frequencies, making those sounds much louder. You can undo that to some extent by identifying the frequencies that get boosted by the room and cut them in the amp so that after the room has its way with them, the overall response is still pretty flat.

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              • #8
                Reading more about PEQ, it seems like my definition for bandwidth is off, as the Q describes (indirectly, through math I still don't fully understand) the spacing, not of the total range of frequencies affected by the adjustment, but instead the range of frequencies between the -3 dB (or +3 dB for cutting) points. The total range of affected frequencies, I surmise, is theoretically infinite.

                Maybe I'll figure this out, eventually.

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                • #9
                  Originally posted by SteveSatch
                  Not the phase, gain, or crossover. I know how to do that, but I've never had a sub with an amp that had EQ features. I'd like to read the proper way to set one up if I ever get one.
                  Steve,

                  in the old UFW/ULW manuals they had a section on the eq

                  go here (thanks Gonk)

                  http://www.prillaman.net/av123/rocke..._manual_v2.pdf


                  Murrel
                  Mitsubishi WD-57772, Outlaw 990, Emotiva LPA-1, Sony PS3, Dish Network HD, RS 760's, Bigfoot, RSS300, ELT525, 2 SSA RUMBA 12

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