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  • Digital Audio Correction / Digital Room Correction DRC

    Thought you might find this to be interesting:



    This is how I did it:

    http://members.cox.net/mikemcd/S2000...rrection.shtml

  • #2
    not sure about this.....*scratches head*
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

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    • #3
      So am I correct in assuming the music is processed and then stored for playback to match the output of the car then? So unless the music is previously processed it won't sound correct?

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      • #4
        Yes, I preprocess the music and store it on an Ipod to play in the car. You can also play unprocessed music using a computer, through a player with a convolver (e.g. Foobar, WMP, etc).

        Standard CDs also work fine - a little better than stock due to the improved crossovers.

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        • #5
          great info here!! what software are you using to generate the sine sweep, capture the impulse response and make all those nice graphs with?


          i am in the finishing stages of part1 of my install - second amp isn't in yet, but i can capture the impulse response of each individual driver. when finished, i will have a 3-way active frontstage plus sub

          i tried using Room eq wizard, but my graphs didn't come out nearly as nice as yours, so i have been looking for an alternative software program

          i am using an ECM8000 with a calibration file to capture the sine sweep through an m-audio mobilepre

          i plan on using offline processed music as well, through an alpine cda-9830, until i can afford a carpc and auzentech xmeridian soundcard

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          • #6
            Sorry we didn't respond to this directly, I remember reading your page from a link someone posted in the DIYaudio forums on the howtoXO thread. It's just not a solution thread works for us. Similar to Accurate by Uli. Here's the problem:

            1) I have a huge music collection as well as many of us do. To convert the music and save it to disk is ALOT of work. And this doesn't work at SQ competions. You are required to use their CD. WHat happens if you change something? Then you have to reconvert ALL the music again? Yikes!

            2) BruteFIR/Convolver is for coders and programmers. I would rather have something I can change on the fly in real time. How am I supposed to tune with bruteFIR or convolver in the car? The car is not anything like home audio. It's a completey different animal. MOST Automatic RTA's don't even work in a car if you ask people who know about what it takes to get Great sound in car. You can use it to help you tune, but I would never rely on it to make corrections for me.

            If you have had good luck with DRC anc convolver and bruteFIR then cool. We were looking for something that mimics current car aduio gear but takes it a step beyond for more flexibility and ease of use. Ease of use is a major key factor. Like I said again, if this method worked well for you cool, but I think most of are looking for something else. The ASIO and VST plugins are very powerful IMO.

            Cheers
            System always under construction


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            • #7
              jmelan:
              The DRC package has a small program that will generate the log-swept sine wave. You can use Adobe Audition to both play the sine wave through your audio system and record the output. However, I put the sine wave in my Ipod so any coloration it generates is also corrected. (Ironically, the original Shuffle has the flattest frequency response: http://home.comcast.net./~machrone/p...playertest.htm ,and I have verified the phase response to be flat.) You can download a fully functional 30-day trial version of CoolEdit, which was the predecessor to Audition. I use Matlab to process and plot the filter and impulse response files. Audition and Foobar have convolvers, in addition to the WMP convolver.

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              • #8
                thanks. i think i found it. that manual is pretty intimidating!

                there seems to be a script in the DRC manual also to process the impulse response through octave (matlab?) and auto generate all kinds of graphs

                i am going to try a run through this today and see what kind of results i get. i am not the best with command line interfaces.

                did you alter your DRC config file to optimize for car audio, or was one of the preset ones ok (minimal, normal, erb...)?

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                • #9
                  jmelan: Yes, this will most likely take you a lot of time. Here is another good guide: http://www.mooneyass.com/DRC/DRCGuidev1.0.pdf . The DRC scripts are designed to work with Octave, but Ocatve is not real Windows-friendly. I got the best results by starting with the config file that Denis uses for his system - in my case, it does a better job of correcting phase.

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                  • #10
                    Hi,

                    How did you change the volume level of your FIR filter?

                    "Volume Correction
                    Because the driver is significantly off-axis to the left speakers and the driver's left leg blocks the output of the left lower speaker, the left channel output was increased by 3db in the FIR filter to match the level of the signal arriving from the right speakers. This helps to center the sound stage and improves imaging."

                    I am measuring a 2.25 dB difference on average in my left versus right channel from my listening postion and can't figure out how to correct for this.

                    Can I do this in Audition?

                    Thanks

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                    • #11
                      Yes, in Audition: Effects / Amplitude / Amplify-Fade.

                      To delay a channel, add samples of zero magnitude to the beginning of the FIR filter and delete an equal number of samples at the end (the number of samples can be calculated using the distance and the speed of sound).

                      To test your work, convolve the swept sine wave with your new filters and play it through your system while recording it. You should get a pretty flat frequency and phase response. The TC files that DRC produces are also very accurate.

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                      • #12
                        thanks, i guess i didn't realize you could edit the filters like a normal sound file.

                        i ran a test run like you had described using a sine sweep in audition and the results were very impressive.

                        i also used foobar to convert some test files made using the erb.drc and optimized.drc files and i am going to listen to those tomorrow to see what sounds best.

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                        • #13
                          If you are looking for the DRC guide

                          You can find it on the way back machine (thank god for that Mr Peabody) at http://web.archive.org/web/200610141...CGuidev1.0.pdf

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