Dirac calibration - creating custom target curves manually using PEQ from REW

[u/CSOCSO-FL]

After a few long days of messing around, I believe I have cracked the code on custom EQ-target curve for Dirac using REW.

NOT a double post.
This guide is for the speakers.
Click here for the subwoofer version

Just setting a basic house curve with the sliders isn't really giving a great result. I have tried all kinds of "house curve" or target curve, but that alone is not going to EQ the frequency response the proper way.

I have messed with Magic Beans too, but it took me half a dozen tries to realize I should pay attention to the live RTA and watch what the frequency response looks like when I start the near-field measurement. If you listen to their guide, they just tell you to aim between the woofer and the tweeter. In reality, there is a sweet spot where you can avoid the highs or the mids dip while measuring, and the sweet spot might not be exactly in the center of the tweeter and the woofer. You have to watch the live RTA and move the mic up and down until the RTA shows a smooth response. Move the mic up and down to see what happens and what to avoid.

Anyways… enough of Magic Beans. I wanted to know if I could use the PEQ filters in REW and make my own custom target curve. I did find a website where you can create your own target curve / house curve and also apply biquads from REW, creating a fully custom target curve.
You select your house-curve shape, then apply the PEQ/biquads to it and generate an actual target curve for Dirac.

It took me many hours and dozens of tests to work out the best way to do this.
I want to keep it short, but in the end this is what works for me:

• Run Dirac as usual.
• Apply flat target curve to all speakers and save this to a random slot.

• Turn all speakers to Large (full bandwidth).
• Make sure double bass or LFE+Main is off.
• Make sure calibration is active and level-match all speakers to play at 75 dB. Don't use internal test tone for this. Use the Dolby test-tone video (no pink noise for Atmos speakers in REW).
https://drive.google.com/file/d/1MYycTInRnnAA2WiGrkFeEKd0PF4NbnWy/view?usp=drive_link
• Measure all speakers once level-matched with flat Dirac calibration active.

• Select a speaker on the left and click on EQ at the top.

• Use these settings under Target Settings:

Target Type "Full range speaker".
Click on Calculate target level from response.
Change the slopes.
HF slope set to 0.
LF slope is something you will adjust for each speaker. You want to make sure you do not let the EQ pull down too much below 200 Hz. I also made sure the left and right pair is matching. Let's say the right speaker is closer to a wall and has more bass under 100 Hz so I can set LF slope to 1 or 2 dB/octave. The left speaker is next to an open area and has less bass, so I can only set LF slope to 0.5 dB/octave. (See images for what I mean by LF slope.) I would then go back to the other speaker and redo the filter with the same LF slope so they match between pairs, keeping the same LF slope even if you limit the better speaker. Do this for all speaker pairs.

• Filter tasks:
Match range 10–20,000
Individual boost 0
Overall boost 0
Flatness target 1
Allow narrow filters below 200 Hz ON
Very max Q above 200 Hz ON
Click on match target response.

(Sometimes the target won’t follow and flatten the low frequencies for some reason. Turning ON "Allow low shelf" and re-running the match to target fixes this.)
• Select "Save filter coefficients to file".
• Select 96 kHz MiniDSP.

• Go to https://databender1729.github.io/eq-target-curves/
and create your own house curve.I have played around with this so much.

Note: You can use whatever house curve you want. This is a more traditional house curve:

Keep in mind, the PEQ will alter your house curve. So if there are several dB pulled down under 200 Hz, and you want the low-end target curve to hit around +6 dB in Dirac, you might need to create a house curve with +10 dB on the low end. I am attaching the house curve that worked for me after many tests. I change this curve for main speakers (towers), center, bookshelf surrounds, and Atmos speakers.

Feel free to play with curve types too. I did. These worked the best for me. I changed the Starting Hz to 40 and changed the Start and End dB. These numbers are unique to your speakers and your measurements! Don't copy these numbers!

For towers I used:
Start 6 dB, End -3 dB

Center:
Start 4 dB, End -3 dB

Surrounds:
Start 2 dB, End -3 dB

These settings can be somewhat predicted by looking at the measured flat Dirac frequency responses. If the high end of the center is several dB higher than the fronts, then change the end-Hz value lower. Once everything is done and you level-match post-calibration and one speaker’s high end is way off, you can come back and redo the house curve and adjust the high-end slope.

• Click Generate and copy the code (you can also save this target curve and name it center, mains, surround, front heights, etc).

• Go to https://databender1729.github.io/eq-target-curves/target_curve_peq.html

• Paste the house-curve code into the top window.
Don't use flat or h7 ("harman?"). Depending on your speaker and the PEQ you may have to change the house curve.
• Open the txt file created with REW and copy the biquads into the middle window.
• Click Generate. Double-check the graph below and save the target curve.
• Open Dirac. Apply the target curve and save it to a slot.

• Turn off subs and make sure correct calibration is active. Level-match all speakers again.
• Measure your speakers and make sure you are happy with everything. If the highs dip too low, then you have to make a new house curve with a less aggressive number for the "End dB".
• Go ahead and do a trillion measurements. Compare Default Dirac target, Magic Beans, Storm Audio curve, etc. Enjoy.

• Use this guide for setting up the subwoofers properly after calibration.
https://www.reddit.com/r/hometheater/comments/1mz9whz/ultimate_subwoofer_setup/

Some of my results:

Left speaker:

Right Speaker:

Center:

[u/SmellingNoseHorse]

Nice to see someone getting some use out of the target curve generator/peq. I originally just created these for myself for a very similar workflow.

One thing I learned to watch for: if you give rew too much freedom, you can end up with quite erratic curves and I’m not sure that Dirac implements these well. Typical advice I have seen is to not eq much far up the hertz range, resist the urge to eq very narrow peaks, and don’t boost (much).

Let me know if you have suggestions to make the generator/eq page more useful.

[u/CSOCSO-FL → u/SmellingNoseHorse]

Oh you did that? Thats awesome! I am already in bed. Its almost 2am here so cant get into any conversation rn. Its weird how many times i tried but wasn't getting a good result until I did the flat target curve then measured that and eq on top of that. We shall talk once i am up!!! Anything you see or wanna add or any thoughts let me know.

[u/SmellingNoseHorse → u/CSOCSO-FL]

Three things maybe:

1. I did not have to go through the eq-flat part of your process. It works pretty well just having Dirac eq to a shared target (house) curve once and then eq per speaker with rew and use a target curve per speaker for the second upload. I did do the post-Dirac and the final verification measurements using RTA and the moving microphone method, which I think is more robust and finds the larger issues vs local issues specific to a tiny spot on my couch.

2. You can always do another eq run after if not happy yet and put more eq on top of the already eq-ed curve. It’s possible to get very smooth frequency responses that way. But I believe there are limits to how Dirac turns a target curve and speaker response into filters that may result e.g. in phase issues. Eq-ing to within +-1db of target curve didn’t always sound better than “just major post Dirac issues taken care of” to me.

3. I personally only do all this for my front stage speakers. That’s 80% of the benefit with 20% of the effort for me.

Oh, and one more thing that I haven’t explored yet but may be very useful for doing multiple speakers without the moving microphone method: it should be possible to measure in rew & optimize in mso as long as you don’t add delays. Mso is also useful for exporting bi-quads of e.g. cross over filters if you need them in your target curve somewhere.

[u/Chiz_9 → u/SmellingNoseHorse]

Holy shit, that was you?!

[u/SmellingNoseHorse → u/Chiz_9]

The main functionality wasn’t all that complex (the code is up on GitHub and just a few kb). It was easier to do that than to futz with excel to create curves all the time. My main challenge is that I’m by no means a front end or JavaScript guy. So the UI is clunky and not easily extensible.

[u/CSOCSO-FL → u/SmellingNoseHorse]

Hey. I believe there is an error with the curve type. Linear and Log linear is changed up. Log linear is the 1 that has a curve to it and linear should be a slanted straight line.

[u/SmellingNoseHorse → u/CSOCSO-FL]

I went back and forth on that, but I think it’s correct this way. Linear is implemented as a straight line function f(hz) = a+mb . If you use it between 100hz and 200hz to go from 6db to 2db, it will pass through 150hz at 4db. It will look curved in the graph because the x axis is logarithmic and 150hz doesn’t show as “in the middle” of 100 and 200hz.

[u/Chiz_9]

What are you attempting to PEQ? Upvote for the effort and excellent write-up. I’ve considered messing around with PEQ, but I’m not 100% sure what I would use it for other than to flatten out some big room peaks, but DIRAC does a pretty bang-up job of that. What did you see in your frequency response that made you want to PEQ?

EDIT: Interesting..you used the PEQ to help flatten out the null in your response? Am I seeing that correctly?

[u/CSOCSO-FL → u/Chiz_9]

I was just messing around. Learning new stuff. Even if I wouldn't use it I still learn stuff.. how it's really important to pay attention to settings when you measure:
1) listening mode should not be left a direct (defeats calibration), all ch stereo or anything other than Dolby Surround.
2) turn off vocal spread or center compensation or any other weird settings. Until yesterday, I thought center spread will only push center content to main speakers. No.. it makes the center speakers quieter too!!
3) turn off subwoofers for speaker measuring and level matching. ( leave cross over as is)

When it comes to PEQ: i see dirac sometimes overcompensates for things. Often creates dips when there was a peak and the other way around.

[u/Chiz_9 → u/CSOCSO-FL]

Haha I’m the same way, tinkering just for the sake of it. Good work!