subtractive EQ half explained

[robin watson]

I found this recently. It goes halfway towards explaining, in a very practical way, what you need to do, then appears to stop. Can someone fill in the gap?

Here's the text:

For those unfamiliar with subtractive EQ, it's instructive to spend some time experimenting with sweepable mids. First, dial in a radical cut-say, 15 dB. (If you have control of the bandwidth, set a narrow Q, as well.) Now, turn the sweep knob slowly from hard left to hard right while listening to how the cut affects the signal at different frequencies. Do the same thing with a 15 dB boost and compare. What you're listening for is how a cut on one side of the frequency spectrum results in a sound quite similar to that provided by a boost on the other side. For example, a low-mid cut (depending on the source, of course) can result in an apparent brightening of the signal-much like what you would get by boosting the high mids.

So....what then?

Robin

 

[robin watson]

I guess he's trying to say that you can achieve the same effect with subtractive EQ without having to resort to boosting EQ. (But I'm pretty aware of that already!) I guess this is an excersise in familiarizing the ear with the concept. Still doesn't tell you 'how' exactly, does it?

 

[fuzzrhythm]

it's just to demonstrate how you can get a perceived boost by cutting in another area.

the way I understand the whole process of subtractive EQ is boost quite a bit with a narrow Q, sweep around until you find something undesirable, then reduce gain on that frequency until the bad sound goes away.

 

[Harvey Gerst]

A big part of understanding subtractive (or any) eq is visualization: seeing in your mind what the eq is doing and visualizing what you want it to do. Let's use a common situation as our example:

You want midrange boost, but you only have treble and bass controls available. If you reduce the bass and treble controls, by -3 dB, then bring up the channel by +3 dB, the bass and treble will be back to normal, but the midrange will be 3 dB louder.

Subtractive eq is a way to increase a desired range by removing an undesired range. Does an instrument need more highs? Try turning down the bass control and boosting the volume instead. Same thiing as turning up the treble.

Most beginning engineers think they need to add more of something to get a desired sound. That starts pushing the equipment harder, increasing distortion, and reducing headroom, especially when combining a lot of channels.

Rather than say, "I need more highs here", think instead, "I need less bass here".

 

[jeap]

the suggestion is a way to get used to sounds and EQ just by "turning knobs" to see what happens

youre never going to get anywhere with EQ if its all a mystery

people used to use simple units with a few knobs or sliders and they would mess around with the knobs to figure out what the thing did


do a websearch for "mixing eq" or related topics. maybe add the word subtractive. there are lots of strategies and templates people use but you have to use your ears to make decent choices

the important thing is to jump in and get started