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.
http://www.madpsi.net/Projects/MR2%2..._SPL_Meter.jpg

I was going to write this out, but I found a webpage that pretty much summed it up.

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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

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All from this page:
http://www.madpsi.net/PMR2%20-%20Stereo%20System.htm

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?
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+or-#

If any more experienced tuners want to add something or point out some flaws, please go ahead.

dude this is awesome to get me started...but i was getting a parametirc. Thanks.

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Originally Posted by Genesisfactor

dude this is awesome to get me started...but i was getting a parametirc. Thanks.

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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.

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.

if you have AIM, use my handle here as my screen name. I would like to talk to you about this more

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.

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.

@JasonWW....you are God. :nw: 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...

this post was made in error

:)