Helpful ReplyHow to adjust EQ to create a flat response for headphones

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rogeriodec
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2017/11/18 19:07:54 (permalink)

How to adjust EQ to create a flat response for headphones

I found this graph that demonstrates the frequency response of a headphone of mine:

In fact it is part of a larger study that is on this page.
Now that I know the distortions of this headphone, could someone tell me how I can adjust the EQ accurately to compensate for these differences and create a completely flat response?
post edited by rogeriodec - 2017/11/18 19:41:39

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mikedocy
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Re: How to adjust EQ to create a flat response for headphones 2017/11/18 21:08:50 (permalink) ☄ Helpfulby rogeriodec 2017/11/18 21:32:25
You could try this:
Try to Match the EQ curve with the Sonitus Equalizer like I did in the photo. I used the blue curve.
Then invert all the gain settings like this:
Set band 1 for -6.1 dB.
Set band 2 for +3.6 dB.
Set band 3 for -5.5 dB.
Set band 4 for -7.2 dB.
Set band 5 for +4.8 dB.
Set band 6 for -7.1 dB.
That should get you closer to flat. You will need to do some final adjusting by ear.
Note: You actual headphone may differ from the graph.  
 
 
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mikedocy
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Re: How to adjust EQ to create a flat response for headphones 2017/11/18 21:14:04 (permalink) ☄ Helpfulby pwalpwal 2017/11/19 11:11:24
Also, look into SonarWorks. This is a program that does exactly what you are asking for.
The problem is that it does not support your particular headphone model: Philips SHB9100.
It does support the SHB9500.
You would have to purchase another headphone that is supported by the program.
 
https://www.sonarworks.com/reference
 
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rogeriodec
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Re: How to adjust EQ to create a flat response for headphones 2017/11/18 21:39:36 (permalink)
Thanks Mike. 
Could you tell me the difference between the blue line and the black line in the frequency response graph?



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mikedocy
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Re: How to adjust EQ to create a flat response for headphones 2017/11/18 22:15:33 (permalink) ☄ Helpfulby rogeriodec 2017/11/20 14:03:40
rogeriodec
Thanks Mike. 
Could you tell me the difference between the blue line and the black line in the frequency response graph?


The blue graph was obtained using a special stand (SF1) for the headphone and calibrated microphones.
It has a soft surface to reduce sound conduction and reflection. It has no "ears".
EDIT: See photo here: http://reference-audio-analyzer.pro/stands.php
 
The black graph was obtained using what  is known as a "Dummy Head" stereo microphone with ears (HDM1).
The headphone is placed on the "dummy head". The ears of the dummy head contain calibrated microphone elements.  
 
That said, perhaps you should try matching the EQ curve of the black curve. It may be a better approximation of
how the headphone actually sounds.
 
And remember... you are never going to get the headphones completely flat just by looking at a chart and trying to match and invert it.  But I am sure you can improve the sound of the headphone if you try.
The biggest improvement I can see would be to take some of the low frequency boost out.
The best way to learn is to do. Set up that EQ and start turning the knobs and learn what works and what doesn't work.
 
Put the Sonitus EQ in your master buss so that the entire mix is Equalized.
Bypass the EQ before you render a stereo mix. You don't want that EQ graph printed to your mix.
 
 
 
 
 
 
 
post edited by mikedocy - 2017/11/18 23:46:24
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pwalpwal
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Re: How to adjust EQ to create a flat response for headphones 2017/11/19 11:13:03 (permalink)
mikedocy
Also, look into SonarWorks. This is a program that does exactly what you are asking for.
The problem is that it does not support your particular headphone model: Philips SHB9100.
It does support the SHB9500.
You would have to purchase another headphone that is supported by the program.
 
https://www.sonarworks.com/reference
 


there is also the toonboosters offering, similar to sonarworks but has more headphones supported https://www.toneboosters.com/tb_morphit_v1.html

just a sec

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rogeriodec
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Re: How to adjust EQ to create a flat response for headphones 2017/11/19 16:30:01 (permalink)
mikedocy
 

The blue graph was obtained using a special stand (SF1) for the headphone and calibrated microphones.
It has a soft surface to reduce sound conduction and reflection. It has no "ears".
EDIT: See photo here: http://reference-audio-analyzer.pro/stands.php
 
The black graph was obtained using what  is known as a "Dummy Head" stereo microphone with ears (HDM1).
The headphone is placed on the "dummy head". The ears of the dummy head contain calibrated microphone elements.  
 
That said, perhaps you should try matching the EQ curve of the black curve. It may be a better approximation of
how the headphone actually sounds.
 
And remember... you are never going to get the headphones completely flat just by looking at a chart and trying to match and invert it.  But I am sure you can improve the sound of the headphone if you try.
The biggest improvement I can see would be to take some of the low frequency boost out.
The best way to learn is to do. Set up that EQ and start turning the knobs and learn what works and what doesn't work.
 
Put the Sonitus EQ in your master buss so that the entire mix is Equalized.
Bypass the EQ before you render a stereo mix. You don't want that EQ graph printed to your mix.
 
 

Mike, the world would be a much better place if there were more people like you! 
Although the site is in Russian, thanks to the fabulous Google translator, it is possible to understand.
And we have to get the hat off for the work of these Russians.
I enjoyed the excitement and created a profile using FabFilter Pro-Q:

 
I used your technique of imitating the graph curve and then invert the frequencies, which in FabFilter is very simple.
 
Actually I went a little further by literally overlaying FabFilter over the original frequency response graph, leaving the plugin window semi-transparent (for that I used this Autohotkey script) and then resizing the window to exactly overlap the vertical and horizontal gridlines . Hence I basically drew the curves of the EQ over the black line of the graph.
The result was excellent. Fewer bass tones, and some variations in mid and treble.
Of course now I have to accustom my ears after so much time using this headphone without the proper calibration.
But now I think I'm on the right way. 

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rogeriodec
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Re: How to adjust EQ to create a flat response for headphones 2017/11/19 16:38:03 (permalink)
pwalpwal
 
there is also the toonboosters offering, similar to sonarworks but has more headphones supported https://www.toneboosters.com/tb_morphit_v1.html


Thanks for the tip!
They also has a profile for my headphone model.
I downloaded the demo version and tested it.
But interestingly, the frequency response of this plugin for my headphone is quite different from the eq I created based on the Russian graphic I showed at the beginning of this topic; mainly in the low frequencies where, instead of reducing them, as it should be, by inverting the excess frequencies emitted by the headphone, on the contrary, their profile increases these low frequencies even more!

The mid and high frequencies are somewhat similar to my EQ, but low frequencies are a serious problem.
Now I wonder, who's right? I bet on the Russians, which show all the variations and methods used for capturing, as shown by Mike in the previous post.

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dubdisciple
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Re: How to adjust EQ to create a flat response for headphones 2017/11/20 05:23:50 (permalink)
Interesting. I was thinking of getting morphit
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pwalpwal
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Re: How to adjust EQ to create a flat response for headphones 2017/11/20 11:48:16 (permalink)
toneboosters is a responsive dev, you should contact him directly if the results are unexpected... i should add that i use sonarworks because morphit wasn't around at that point

just a sec

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rogeriodec
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Re: How to adjust EQ to create a flat response for headphones 2017/11/20 12:03:02 (permalink)
I contacted Tonebooster and he deconstructs the argument that a headphone should have a flat response.
Now I was very intrigued.

Here is the conversation:
 
"Unfortunately it's not really possible to compare graphs between different measurement protocols. Firstly, the measurements you point to are 'blocked ear canal' measurements, while Morphit takes the effect of the ear canal into account (e.g. we are using open-ear canal measurements). As a result, measurements will look very different.

 
But more importantly: headphones should never be tuned flat, which seems the underlying assumption of the measurements you linked to. Have a look at the published work done by ourselves and for example Sean Olive from Harman:
 
https://asa.scitation.org/doi/10.1121/1.4984044
 
The ideal headphone response is not flat, but instead equal to that of a flat loudspeaker in a well-treated room. If you have a look at the paper linked above, you'll see that headphones are virtually never flat - intentionally so! The response of a flat loudspeaker in a room (at the level of the ear drum) will have quite some bass boost.  By using that as target curve, we ensure to have maximum consistency between headphones and loudspeaker playback, which is the primary goal of Morphit."
 
Then my new question:
 
"I'm not an expert, but at this link (http://reference-audio-analyzer.pro/stands.php) you can check all the measurement methods they used.Regardless of the considerations, there is a fact: my reference monitors (Tapco S5) always sounded with less bass than my headphone.
When I created an EQ manually, as you can see in this topic (http://forum.cakewalk.com/How-to-adjust-EQ-to-create-a-flat-response-for-headphones-m3686014.aspx), based on the graph I reported, the headphone basses decreased significantly, getting much closer to the reference monitor, unlike Morphit, which, as I had said, instead of softening the basses, made them even louder, thus getting even more different from my reference monitors.
I usually mix and master with headphones and then I'm amazed at your claim that headphones can not be flat. If so, what is the purpose of Morphit?"
 
And his new response:
 
"Like I said; have a look at the paper I've linked in my previous email, and have a read of Sean Olive's work (he has a lot of papers in the Audio Engineering Journal about headphone target curves). None of the preferred target curves is flat, in fact they are anything but flat!!
 
Morphit is all about consistency between headphones and loudspeakers. That means that the target curve of Morphit should be that of a flat loudspeaker in an acoustically well-treated room. As you can see in Sean's work, that response has quite some bass boost due to interaction of the flat loudspeaker and the reflections in the room. Hence at the level of the eardrum, there will be a considerable bass boost.
 
If we would tune a headphone flat, it would have insufficient bass compared to loudspeakers, hence inconsistent reproduction of timbre. This is one of the big shortcomings of all measurements reported on the site you linked to (and a greatly misunderstood issue in the audio engineering world).
 
That said: Morphit has all the tools to modify your target curve if you'd like to. It can even simulate a flat target at the ear drum (choose flat response as target curve for your headphones). If you do that experiment you'll quickly find out that a flat target curve is the wrong answer. Additionally you can customize the EQ as well by using the marametric EQ; feel free to reduce the bass levels in a personalized profile.
 
Last but not least: it could well be that the Philips headphone we used for measurement is different from yours. There could be relatively much bass in yours, or a leaky coupling between the headphones and our professional dummy head (worth 60.000!) causing a weak bass in the measurement. Unfortunately we've seen that headphones can vary quite a bit from one sample to the next for some brands.
 
Cheers,
Jeroen"
 
 


 
Where is the truth?
 

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Re: How to adjust EQ to create a flat response for headphones 2017/11/20 12:57:47 (permalink)
+1 for SonarWorks here.  It definitely lessens the headphone effect for me.  I have the cheapes pair of headphones for mixing:
https://www.amazon.com/Superlux-681-Dynamic-Semi-Open-Headphones/dp/B002GHIPYI/ref=sr_1_1_sspa?ie=UTF8&qid=1511182645&sr=8-1-spons&keywords=Headphones+681&psc=1
 
SonarWorks has a curve for them!  They sound great using the curve.  VERY BOOMY without it.
 

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Re: How to adjust EQ to create a flat response for headphones 2017/11/20 13:57:55 (permalink) ☄ Helpfulby rogeriodec 2017/11/20 14:03:06
My initial reaction to the first curve you posted was that those headphones should be fine without EQ. There are far more expensive headphones out there that don't look as good.
 
Yeh, we all hate seeing all those little hills and valleys, but in truth they are more trivial than they appear, and yours are easily within the window of what can be ear-trained away.
 
Looking at graphs, it's hard to make a distinction between significant anomalies versus inaudible variations. Valleys are less significant than peaks, and narrow valleys are often completely inaudible. But even setting aside the question of which of the bumps are important, flattening the response may still be a wild goose chase.
 
First, the assumption that "flat" is the ultimate ideal is predicated on a significant presumption: that your own hearing is flat. It isn't. 
 
Second, headphones should have a slight emphasis in the bass to compensate for the fact that they are so close to the ears. Unlike speakers that are 3-10 feet away, they don't get the acoustical assistance from the room that tends to boost bass. 
 
All that said, if I was applying EQ compensation for those cans, I'd be more concerned with the midrange dip between 1-2 KHz. Those are the most critical frequencies for mixing. I'd experiment with a modest (2-3 dB) boost there and leave the rest alone.


All else is in doubt, so this is the truth I cling to. 

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