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Does Equalizing actually distort music?

post #1 of 35
Thread Starter 

Hi so I've a question about equalizing. For the longest time I've heard from people that equalizing distorts the music you are listening too, but is this true? I've always used itunes equalizer. If I want to emphasize a region I would keep that frequency the same but lower all the other frequencies and than increase the volume. So what is your opinion on this?

post #2 of 35
Quote:
Originally Posted by slayerming2 View Post

Hi so I've a question about equalizing. For the longest time I've heard from people that equalizing distorts the music you are listening too, but is this true? I've always used itunes equalizer. If I want to emphasize a region I would keep that frequency the same but lower all the other frequencies and than increase the volume. So what is your opinion on this?

Not in ways other than intended. xnor did some measurements of software equalizers a while back and they all had distortion well below audible levels IIRC.

 

The main problem with graphic equalizers like iTunes is that they're not very accurate. They're doing things that you wouldn't expect them to do. This especially holds true if you're lowering most of the bands down and trying to get them to the same level by eye(lowering the pre-amp should negate the need for subtractive equalization though).

 

EDIT: Here's the link to xnor's measurements: http://www.head-fi.org/t/526507/audio-player-equalizer-resampling-measurements


Edited by chewy4 - 7/2/13 at 12:18pm
post #3 of 35

Equalization *corrects* distortions. An imbalanced frequency response not only doesn't sound natural, if there are spikes in the wrong places, it can cause clipping. A balanced EQ will make transducers work more efficiently and avoid overdriving in certain frequencies.

post #4 of 35
Where is Xnor when you need him?!

EDIT: He created the EQ UI that I use for Foobar, he is quite knowledgeable on this subject.
Edited by White Lotus - 7/3/13 at 5:57am
post #5 of 35
Quote:
Originally Posted by slayerming2 View Post

For the longest time I've heard from people that equalizing distorts the music you are listening too, but is this true?

Technically, anything that changes the audio in any way is "distortion." So going by that overly board definition EQ adds distortion. But I disagree with that use of the word. To me, distortion is the addition of new frequencies that were not present in the original source. The most common type of distortion occurs when you overdrive a circuit. So in broad terms, applying EQ does not distort the audio. However, it does change the frequency balance. Which of course is the whole point!

--Ethan
post #6 of 35

Yeah, what you are referring to, Ethan, is linear distortion but when people speak of distortion they usually mean nonlinear distortion.

 

A simple test to see whether an EQ adds distortion is to e.g. add a +5 dB boost followed by an identical -5 dB cut and compare the output to the input.

 

 

Software EQs usually operate in 32 or even 64 bit floating point numbers, so they achieve a higher signal-to-noise ratio than even perfectly recorded 24 bit files and extremely high dynamic range.

Some EQs, like Electri-Q, have an analoge mode that adds nonlinear distortion, but if you set it to digital it will be clean.

 

Last time I checked the iTunes EQ it was not exactly precise, that is a smooth curve in the user interface resulted in a jagged frequency response. You could call that unwanted linear distortion. Because of that, lowering all sliders but the ones you want to "boost" may result in something you'd not expect.

I never tried the simple test mentioned above, but could do so if you want.


Edited by xnor - 7/3/13 at 3:11pm
post #7 of 35
Quote:
Originally Posted by xnor View Post


A simple test to see whether an EQ adds distortion is to e.g. add a +5 dB boost followed by an identical -5 dB cut and compare the output to the input.

 

I read that many EQs have different Q factors for boosts and cuts, this would make the result of your test not identical to the input even if no distortion is added wouldn't it?

post #8 of 35

That can indeed be the case. If you have to tweak the inverse filter by hand you won't get a perfect result and the output-input will probably only null down to a couple of dBs.

 

But that's just the quick 'n dirty check anyway. With the right tools you can not only analyze if the filter shapes conform to what the user configured but also the phase response, or if the EQ adds anything that doesn't belong.

 

IIRC, Electri-Q for example has a DC blocking filter and also oversamples internally which causes some anomalies near half the sampling rate if you have eco disabled. So enabling eco disables those "features".

post #9 of 35
I haven't had a equalizer that introduced noise or distortion since I had an old 10 band graphic EQ back in the 80s... and the problem there was more with ground loops than anything else. Digital EQs are as good as I could hope for (with the exception of the lousy EQ built into iTunes, and that is a problem with spill all over.)
Edited by bigshot - 7/4/13 at 11:56am
post #10 of 35

All this talk about the iTunes EQ got me curious.

 

Quick and dirty. Orange is a white noise 16bit WAV straight from Audacity. Green is the same file played through iTunes, EQ disabled. Purple is the same as green, except all levers but the 1kHz one pulled down to -12dB.

I don't know about the orange/green difference, but the green/purple sure show a lot of linear distortion. Is this what shoddy software-engineering looks like?

 

post #11 of 35

Exactly what I meant in #6. With lots of hand tuning you could probably get a more or less flat FR above/below 1 kHz, but then the user interface sliders will look weird. biggrin.gif

post #12 of 35
Thread Starter 
So should I use the iTunes equalizer?
post #13 of 35

Depends on your configuration (might work well if you just pull a slider down a bit), but personally I wouldn't want to use it.

post #14 of 35
Thread Starter 
Quote:
Originally Posted by xnor View Post

Depends on your configuration (might work well if you just pull a slider down a bit), but personally I wouldn't want to use it.

What's the harm if I just lower the frequencies I don't want to be as prominent? 

post #15 of 35
Quote:
Originally Posted by slayerming2 View Post

What's the harm if I just lower the frequencies I don't want to be as prominent? 

 

It will not have a flat response even if you lower all frequencies by the same amount.

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