Equalizers effect on volume, quality, and tone

Special Interest Groups Audio Processing
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Question 1: In regards to EQ adjustments I’ve always read decreasing is better than increasing (for less distortion). Is this true?

Question 2: In this example, is…

“decreasing bass -6db, mid -3db, leaving treble 0, then setting volume to -18rms”

exactly the same as

“decreasing bass -3db, leaving mid 0, increasing treble +3db then setting volume to -18rms” ?

For this example also assume it is just a 3band graphic EQ to lessen the factors.

  • Hope I posted this in the right place/and hope AF keeps a place one can post general editing (processing?) and how-to questions.
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IMO it all depends on what you consider as unacceptable distortion. What’s it sound like? I have no idea.

The only time I’ve heard it was when using Amplify to reduce one clipped bass wave on a Low Pass filtered/Amplified mono bass boost channel duped from a 44,100Hz rendered stereo channel. It produced a tiny crackly, crunchy sound in Audacity.

It’s always best to start out fixing sound problems at the point of capture from what the mic picks up during recording. This applies to digital photography as well where getting it right in front of the camera involves strategic placement of plenty of full spectrum lighting with a good lens is the equivalent of getting it right in front of the mic with quality equipment and placement.

At least you can sample that raw audio signal at much higher sample/bit rates than 44,100Hz/16bit. Garbage in/garbage out so goes the digital processing mantra. The dirtier the original recorded signal the more distortion applying edits in post.

I would suggest you not make this more complicated than it has to be and just listen to your results and whether they can sustain minimal distortion when adjusting the volume louder on your listening device which should be judged through headphones because the listening dynamics of speakers can hide a lot of dirt.

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Question 2: In this example, is…

“decreasing bass -6db, mid -3db, leaving treble 0, then setting volume to -18rms”

exactly the same as

“decreasing bass -3db, leaving mid 0, increasing treble +3db then setting volume to -18rms” ?

Theoretically, yes it’s the same. In the real world, you might get differences depending on the design of the equalizer.

Question 1: In regards to EQ adjustments I’ve always read decreasing is better than increasing (for less distortion). Is this true?

If you are working with a digital audio editor (like Audacity) you can avoid clipping (distortion) by adjusting the overall level before you save to an integer format (such as regular 16-bit or 24-bit WAV). You can boost as much as you want temporarily, but you may need to bring down the overall level before you render.

The Amplify effect will default to whatever change is needed (up or down) to set the peak(s) at exactly 0dB. After equalizing, it’s a good idea to at least check your peaks by running Amplify, even if you don’t end-up applying the effect.

Cut, rather than boost is still a good general rule. But, there may be times when it makes more sense to boost.

The -18dB RMS level doesn’t relate to clipping. If the peaks go over 0dB, you are in danger of clipping. Some files will clip at -18dB RMS, and some won’t depending on the peak-to-RMS ration of that particular recording. (Regular WAV files files are limited to 0dB, and you analog-to-digital converter and digital-to-analog converters are also limited to 0db.)

Note that equalizers can sometimes can sometimes end-up boosting the peaks when you only cut a frequency band. This is due to different frequencies getting phase-shifted differently (a side effect of filters/equalization). Basically, the peaks from different frequencies get moved-around a tiny bit, and they add-up differently after EQ, which makes some peaks higher and other peaks lower.

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Thanks, Doug, Tim