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  • Rough tune on your EQ

    I'll tell you how to do a quick tune on the EQ. First, you want to use the graphical EQ as the parametric is fairly advanced to use.
    You will need to buy a radioshack digital spl meter for about $40.


    I was going to write this out, but I found a webpage that pretty much summed it up.
    One popular way one can tune their system is by watching the frequency levels on the RTA while tweaking the frequencies with an equalizer. Access to an RTA, however, can be difficult and expensive.

    If you are content with a rough tune to get rid of the major resonances and peaks, and cannot afford an RTA, you can purchase a Radio Shack sound pressure level meter (dB meter) for $40.00 (digital).

    The Radio Shack meter is fairly consistent (standard deviation is about 0.5-1.0dB) and accurate - especially when measuring the midrange. It maxes out at 125dB. Various corrections are available on the internet in order to improve accuracy. When measuring using "slow" response and "C" weighting, the following corrections seem to be most accurate:

    10Hz +20.5
    12.5Hz +16.5
    16Hz +11.5
    20Hz +7.5
    25Hz +5
    31.5Hz +3
    40Hz +2.5
    50Hz +1.5
    63Hz +1.5
    80Hz +1.5
    100Hz +2
    125Hz +0.5
    160Hz -0.5
    200Hz -0.5
    250Hz +0.5
    315Hz -0.5
    400Hz 0
    500Hz -0.5
    630Hz 0
    800Hz 0
    1KHz 0
    1.25Khz 0
    1.6KHz -0.5
    2Khz -1.5
    2.5Khz -1.5
    3.15Khz -1.5
    4KHz -2
    5KHz -2
    6.3KHz -2
    8KHz -2
    10Khz -1
    12.5KHz +0.5
    16KHz 0
    20KHz +1

    After purchasing the SPL meter , you would then make a test tone CD filled with test tones of various frequencies at a 1/3 octave step. You can then measure the dB of various frequencies and either boost or cut the frequency with an equalizer. You can download the MadPSI test tone CD by right clicking and "save target as..." this link. The file is compressed by WinRar, and each sound file is in mp3 format (high quality variable bit rate). The compressed file should have the following mp3 files:

    20Hz
    30Hz
    40Hz
    50Hz
    60Hz
    70Hz
    80Hz
    90Hz
    100Hz
    125Hz
    150Hz
    175Hz
    200Hz
    225Hz
    250Hz
    275Hz
    300Hz
    350Hz
    500Hz
    600Hz
    800Hz
    1000Hz
    1200Hz
    1600Hz
    2000Hz
    2200Hz
    2500Hz
    3200Hz
    4000Hz
    5000Hz
    6000Hz
    8000Hz
    10000Hz
    12000Hz
    14000Hz
    16000Hz
    18000Hz
    20000Hz
    Brown noise
    Pink noise
    White noise
    All from this page:
    http://www.madpsi.net/PMR2%20-%20Stereo%20System.htm
    1999 Black Pontiac Trans Am
    CarPC's in F-bodies
    How To Relocate Climate Controls on the 97-02 F-body Cars
    (AMD Sempron 3000+, Opus 150)
    Car PC system is out, Alpine system is in.

  • #2
    Make sure your gains and x-overs are adjusted for the best most realistaic sound quality. Make sure you tone controls such as bass, treble, loudness etc... are all turned off. You want to make sure you not corrupting the freq responce in any way. If your using rear speakers, turn those off for tuning. Once you have your EQ set up you can go back and tweak later.

    Get some graph paper, write down all the frequencies in a row with a space by them so you can fill in the SPL number. Then position the SPL meter on the center console facing forward or maybe a bit higher like on the top of the passenger seat. Set it to slow and C weighting. Adjust your volume on the test CD so that you can hear the low frequencies without overpowering your mids or highs. You will need to make a note at what volume you are using on your headunit so that these measurements are repetable. You might also pick a middle frequency like 2k and note the volume. That way if you adjust your gains and the volume number on the head unit changes you can play the 2k note and reset the volume.

    Sit in the drivers seat and go through the tracks with the CD palyer or PC set to repeat the track. Calmly watch the SPL reading as it may not stabalize. I had to sometimes write down the average reading, but Iwas using a test CD, not the downloaded one mentioned above. Go from one freq. to the next and write down the SPL reading. You'll need to adjust the range on the meter as the volume gets louder or quieter.

    Once you get all the freqs. wrote down you can use the graph paper and treat each line as one dB. Graphing them out will help create a better visual representation. At this point you may want to use the correction chart listed above. I never knew one existed, but I've only used RTA for the last several years. Assuming the correction list is correct, go ahead and use it.

    Now comes the hard part. Looking at the curve and deciding what needs to be corrected. You can start by looking for peaks. If a single peak in the response curve (not the EQ curve) is higher than 3 or 4dB compared to the adjacent freqs, then drop it down to so it's within no more than 2 dB higher.
    Then look for dips in the same way.

    Your not trying to get the response curve (not the EQ curve) perfectly smooth nor perfectly flat. You just want to get rid of the peaks and dips. You want to use the least amount of correction possible which is why I didn't say to flatten the peaks or dips.

    At this point you want to start making corrections in groups. No more individual freqs. At this point it gets real hard for me to describe the type of curve you want. You can try specific freqs you think need more volume by playing some high quality recordings. Stuff that was recorded accurately. Add a little peak at a specifc freq you think needs to louder. If it sounds good, adjust 2 or 3 bands on either side of that center freq. so that you don't create a big peak. You want the response curve (not the EQ curve) to be fairly smooth between the bands. I don't think it matters too much what the EQ curve looks like, but if you see a big dip or peak on your EQ curve, like 4 or 5 dB more than the bands next to it, then you might want to back that down or up a little. The reason being speakers don't usually create such peaks or dips in such a narrow frequency, so it may be the result of reflections or absorbtions in the car. You also don't want to over correct.

    Hopefully using this technique will give you a nice, but not quite polished tune. It takes more time compared to using an RTA, but it's cheaper and you can do it yourself. Remember to keep the windows up and the don't let outside noises interfere with your readings. Make sure you save the EQ settings when your done. Just in case, you might want to go through all your EQ settings freq by freq and write them down. That way you can go back and adjust your EQ very quickly if you need to. Or if you switch EQ's the new one can be set up very quickly.

    freq?
    ----
    +or-#

    If any more experienced tuners want to add something or point out some flaws, please go ahead.
    1999 Black Pontiac Trans Am
    CarPC's in F-bodies
    How To Relocate Climate Controls on the 97-02 F-body Cars
    (AMD Sempron 3000+, Opus 150)
    Car PC system is out, Alpine system is in.

    Comment


    • #3
      dude this is awesome to get me started...but i was getting a parametirc. Thanks.
      Carputer Progress: Here we go again...

      THE GF THEME
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      Genesis has class
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      before your a__;)

      Join the fight against carputters. EMAIL ME!

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      • #4
        Originally posted by Genesisfactor
        dude this is awesome to get me started...but i was getting a parametirc. Thanks.
        Why parametric? Do you know how to use one?
        They can be a lot more complicated to set up.
        Then you have true parametric as well as quasa-perametric (sp?).
        Which one do you have? Or what model is it?

        You can still graph your response with the EQ off or flat like I mentioned above, it's just a different technique to get the response smoothed out and sounding good.
        1999 Black Pontiac Trans Am
        CarPC's in F-bodies
        How To Relocate Climate Controls on the 97-02 F-body Cars
        (AMD Sempron 3000+, Opus 150)
        Car PC system is out, Alpine system is in.

        Comment


        • #5
          i wanted a Alpine 3402 eq, since i need a 4 channel eq and it was good...but its parametric. Basically, i had a thread on what eq to get that's still on page one. Will was very helpful, though he liked the high q 15-30 bbadneqs, whcih offer superior tuning, but way way way beyond my needs oand outta my league...which i understnad the logic of never needing to upgrade my eq again,, but until you little tutorial right there, i would totally mess up. I was going to use it as my primary eq to nomralize the sound, and then use the built in eq on the NX as my "to play with " eq to boost any responses that i wanted.
          Carputer Progress: Here we go again...

          THE GF THEME
          Genesis has speed
          Genesis has class
          Genesis sent money
          before your a__;)

          Join the fight against carputters. EMAIL ME!

          Comment


          • #6
            if you have AIM, use my handle here as my screen name. I would like to talk to you about this more
            Carputer Progress: Here we go again...

            THE GF THEME
            Genesis has speed
            Genesis has class
            Genesis sent money
            before your a__;)

            Join the fight against carputters. EMAIL ME!

            Comment


            • #7
              I don't use AIM, sorry. What company is that, AOL? I do have MSN messenger.

              For multiple channel use, probably your best bet is the expensive Alpine PXA-H700/701.
              It has 5 31 band EQ's plus 10 bands for the sub. The digital input is the best part of this unit. Plus you get digital x-over as well as digital time alignment.
              I picked one up for $480 used.
              Is that possible for you or is way too much money?

              Those cheaper EQ's are decent if your using a regular headunit, but for a car pc you are much better off adding a $30 sound card with an optical out or buying a coaxial to optical converter for your mobo's digital out and then going directly into the Alpine unit. This unit can do it all!

              Are you sure you need to EQ the rear channels? Usually they are just rear fill and can hardly be heard. They will also typically be just mids with no tweeters to prevent the imaging from being pulled to the rear. If you can get by without rear EQ (I don't even use rear speakers) then there a lot more EQ's out there that can get the job done. Before I got the Alpine I had a Rockford EPX2. It was a 28 band EQ with digital x-over and preamp. It is great for a 2 channel setup that has an analog source and can be found used on e-bay for maybe $300 or so.

              I haven't really messed with any EQ's lower than that. Before the EPX2 I had a pair of mono Audiocontrol EQT's. They were OK, but the noise floor was a bit high.

              Another one you could look into is the H700's little brother, the H510.
              http://caraudiosecurity.com/shop/pro...ts_id/425.html
              http://cgi.ebay.com/ALPINE-PXA-H510-...QQcmdZViewItem
              They aren't the best EQ around but they do have the digital input plus lot's of other features and sell for $150-$200 used. They pack a lot of performance in a fairly cheap package. If you couldn't swing the H700 then the H510 would be your best bet. Using the 6 channel digital input will greatly reduce your noise floor and improve your overall sound quality.
              1999 Black Pontiac Trans Am
              CarPC's in F-bodies
              How To Relocate Climate Controls on the 97-02 F-body Cars
              (AMD Sempron 3000+, Opus 150)
              Car PC system is out, Alpine system is in.

              Comment


              • #8
                With parametric EQ's you have to look at how many bands you have to play with and decide how to best utilize them. You don't want to waste all of them taking care of peaks and dips. Maybe a few big peaks or dips, but the other bands need to go towards actual tuning.

                For those that have a parametric EQ I can make suggestions once you have your readings worte down from the SPL meter.
                Use this list or one like it and fill in the SPL readings next to the freqs:
                20Hz
                25Hz
                31.5Hz
                40Hz
                50Hz
                63Hz
                80Hz
                100Hz
                125Hz
                160Hz
                200Hz
                250Hz
                315Hz
                400Hz
                500Hz
                630Hz
                800Hz
                1KHz
                1.25Khz
                1.6KHz
                2Khz
                2.5Khz
                3.15Khz
                4KHz
                5KHz
                6.3KHz
                8KHz
                10Khz
                12.5KHz
                16KHz
                20KHz

                Based on this and what EQ you have I can make some suggestions.
                1999 Black Pontiac Trans Am
                CarPC's in F-bodies
                How To Relocate Climate Controls on the 97-02 F-body Cars
                (AMD Sempron 3000+, Opus 150)
                Car PC system is out, Alpine system is in.

                Comment


                • #9
                  @JasonWW....you are God. I've been waiting for a write up like this for a long time. I've been using the parametric EQ on my RUX C701 under the impression that it would be easier to tune (since I assumed that you specify the curve you would like to see, and just set the DB's on the frequencies) but I was always so completely off. I'll use this guide along with the graphical EQ tonight and let you know how it goes...
                  PostCount++


                  - SrCsTc's Bezel
                  - Alpine W200/H701
                  - ED Nine.2X
                  - OZ Matrix Elites
                  - ED Nine.1
                  - Idmax 12's

                  Comment


                  • #10
                    Flat sound...

                    this post was made in error

                    Comment


                    • #11
                      I have a couple quick questions regarding the Alpine H701:

                      What is Graphical EQ Defeat? Should it be on or off?

                      In your first listing, you have the different frequencies followed by different numbers. For example:

                      10HZ +20.5
                      12HZ +16.5

                      Is +20.5 the suggested starting point for the db settings? The alpine only goes up to +/- 9db's on all frequencies...do different eq's go higher than 9db. Am i misinterpreting that these are suggested starting points? I am curious to see what others have their frequencies set at...

                      Edit: Nevermind, I read that over again...those settings are for the RadioShack device....i see
                      PostCount++


                      - SrCsTc's Bezel
                      - Alpine W200/H701
                      - ED Nine.2X
                      - OZ Matrix Elites
                      - ED Nine.1
                      - Idmax 12's

                      Comment


                      • #12
                        The Defeat button turns off the EQ (whichever one your using), MX, bass compensation, etc... but not the x-over in order to protect the speakers. Any time you use the EQ you want to make sure the Defeat button is turned off. It's nice in that you can hear the differences between a flat EQ and the changes you've made by switching back and forth. If you have the H700 then try not to use the MX or bass compensation as they tend to muddy the bass and change all kinds of things.

                        That first list is the correction numbers for the digital Radio Shack meter. Anything under 20Hz should probably be blocked anyway. There's pretty much no music down there unless you listen to specially recorded albums that have cannon blasts or pipe organs. They can play that low, but you will also need the subs and the power to reproduce them otherwise you'll just damage your equipment. In fact, the H700 has a high pass filter on the subs that you can set to 20Hz and a 30dB slope to act as a subsonic filter.

                        Anything below 20Hz is considered subsonic and usually below the threshold of human hearing. You will feel it though, like an earthquake, but you won't hear anything. Usually subsonics will cause your woofers to flap around wildly.

                        I want to write up a philosophy for EQ tuning as well. I just don't have time right this minute. Basically do as much sound shaping as you can with speaker positioning and crossovers so that you have the smallest amount of correction as possible with the EQ.
                        The EQ is sort of the last resort and needs to be as little as possible.
                        Always reduce the peaks in your cars response first as they will be the most noticable to your ears.
                        It's always preferable to cut a freq than it is to boost a freq. becausing boost will add some distortion.
                        I'll try to add more in the next few days.

                        If anyone does use the Radio shack digital meter and plot their cars response, post it up here so I can see it. I'll point out the areas that need attention. We'll try the x-overs first as well as the amp gains to get the sound balanced as much as possible before seeing what EQ corrections need to be made. You want to shoot for no more than about 4dB of correction on any particular freq. It all depends though. Just don't overcorrect. Most view the EQ as a crutch, but it can really make the difference between so-so sound and really spectacular sound, especially in a car setup. Cars are just ugly beasts to a sound system. No doubt about that.
                        1999 Black Pontiac Trans Am
                        CarPC's in F-bodies
                        How To Relocate Climate Controls on the 97-02 F-body Cars
                        (AMD Sempron 3000+, Opus 150)
                        Car PC system is out, Alpine system is in.

                        Comment


                        • #13
                          Thank you for all the advice. I just purchased the radio shack digital sound level meter (it was $49.99) and will be tuning my system tonight. I plan to plot down all of my recordings and I'll try and record every step. I'll post picks and comments. I'll stick your guide and post the updates.
                          PostCount++


                          - SrCsTc's Bezel
                          - Alpine W200/H701
                          - ED Nine.2X
                          - OZ Matrix Elites
                          - ED Nine.1
                          - Idmax 12's

                          Comment


                          • #14
                            Just keep in mind all the little things you need to do before plotting out your cars freq response. Turning the tone controls to zero, etc.. Then adjust your gains and x-overs to get the best sound. Get it sounding as best you can THEN plot everything out and start the EQ tuning procedure. Depending on your components you may need to adjust the signal level from the source to the amps to keep the noise floor as low as possible. That's a whole other subject.

                            I haven't really heard the results of that downloaded test tones. I hope they are at the proper levels. It also helps to have some well recorded albums. There are several specialty CD's out there. One of my favorites is Sound Check: Professional Audio Test Disc (UltraDisc II) (see below)

                            Whatever you use, try and focus on getting the vocals to sound natural and realistic. If you can get the vocals, male and female, sounding like they are in the car, then your way ahead of the game. On the above CD, if you look at the tracks you will see a variety of instruments. Tracks 60-79. Stuff like that can really help you tune. Plus it's also good to boost certain freqs up and then down and listen to what part of the music it effected, just to help you develop an ear for what sounds are at certain freq. It really helps to hear a sound and you know what freq that is.

                            Once you get the plot of your car and fix the obvious flaws in the response you still need to adjust the overall tone of the system. It is NOT going to be a flat line from 20HZ-20KHz. This is where things get tricky and personal preference come in. If you get this far, let me know.
                            Attached Files
                            1999 Black Pontiac Trans Am
                            CarPC's in F-bodies
                            How To Relocate Climate Controls on the 97-02 F-body Cars
                            (AMD Sempron 3000+, Opus 150)
                            Car PC system is out, Alpine system is in.

                            Comment


                            • #15
                              haha, ya know, i'm just rereading this and i didn't get your msn. (i have yahoo as well). I'm 2 days and hopefully no bidders away from the alpine. Took a while, but i was having issues with the original seller, among things. PM me. I'll do some tuning when i get the last component (6.5 rear- i'm well aware that rear fill isn't neccessary, but i am attempting to lean more towards HT than CA)

                              Also, would you suggest that i use the 7 bands for the front and use the rear as complete fill or do the 3/4 front/rear eqing that i have the option of? Speakers are infinity reference.
                              Carputer Progress: Here we go again...

                              THE GF THEME
                              Genesis has speed
                              Genesis has class
                              Genesis sent money
                              before your a__;)

                              Join the fight against carputters. EMAIL ME!

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