EQ terminology help for a newbie

[Bermaster]

Just wondering if someone could post some general info about EQ for me. It would be helpful if you could describe it in relation to the Digi EQ II plugin. I understand that boost means to increase the gain and cut means to descrease the gain, but what does it mean when someone says something like:

"In your overheads, remove everything below 100 hz"

Remove? How does this translate to the parameters in the Digi EQ II plugin. Any info (sites, articles, etc.) on basic EQ understanding would be great too.

Thanks in advance.

[albee1952]

Remove can mean 2 things. 1-use a shelving EQ to turn everything below 100HZ down, or 2-use a high-pass(aka low-cut) filter to "remove" the frequencies below 100HZ. A high-pass filter(same thing as a low-cut filter) will have a steeper slope than a shelving filter, and is usually more desireable for getting rid of frequencies that you do not want on a track. Vocals usually get high-pass around 100 or higher(unless you are recording a bass singer). I'll assume maybe you aren't up on some of these terms so here's a little more info. EQ filters come in 2 basic styles(other specialty filters exist but let's stay basic), peakng and shelving. Peaking means that if you boost 6db at any frequency, the shape of the curve will rise (starting below the center frequency), peak at the chosen frequency and fall back above there. A shelving EQ (let's pick 500HZ for example) when set to boost, will boost from the chosen frequency and NOT come back down(creating a "shelf" if you look at a graphical picture of the curve). The basic tone knobs(treble and bass) on a home stereo are shelving filters. Many parametric EQ's offer a choice with a switch(on the high and low if it has 3 or more bands available). Try googling parametric EQ and see what you find out there. I bet when you see a picture of it, a lightbulb will go on over your head.

[Bermaster]

Thanks so much, now I just need to relate this to the EQ II plugin, thanks...

[timebandit]

This question is a bit general for this forum, but I'll try to give you a basic outline. There is a good overview article archived at Sound on Sound (magazine) here. Also check your local library for books on audio. Modern Recording Techniques is a standard. Or just go to the bookstore and read the EQ chapters in books you find there! haha

There are three basic parameters to any EQ:

Frequency - which is the frequency around which the EQ-ing should be centered.

Q - describes the width of the curve (upwards if boosting, downwards if cutting) that is created by the EQ. A smaller number = wider curve = more frequencies affected by the EQ. Opposite for larger numbers.

gain - in the case of EQ II, a positive gain is a boost and a negative gain is a cut, which you said you understand.

Now there are different types of EQ which are represented by the three selectable little curve shapes on the EQ II. The left most one that looks like a ramp leading up is a low-cut or high-pass filter (not that confusing, just think of the name: you are CUTTING the LOWS or letting the HIGHS PASS). When you select that filter it gradually cuts the frequencies from your center frequency downwards. This is what someone means when they say 'cut everything below 100Hz' You are not actually cutting EVERYTHING, as the filtering is gradual, but for ease of communication we just say that! Put it on a track and everything below your center frequency is affected. Try it, you'll see.

Now the second type of filter (the circle with the horizontal line through it) lets you select the frequency and Q as descirbed above and boost or cut defined range of frequecies. This seems to be the type you are familiar with.

The third type is the opposite of the first. It is a low-pass or high-cut filter. When you use this type, everything ABOVE the chosen frequency is affected. In this case cut. There are 'shelving' versions of these EQ types which also allow you to boost everything above (in this case) a frequency, but they are not included on the EQ II.

I hope that general info helps.

Tom

[Bermaster]

This is all great stuff, thanks!

[IntelDoc]

Shoot! I remove (cut) 1.2K and below for the overheads.



Doc

[Bermaster]

Now, let's say I wanted to do something like "In your overheads, remove everything below 100 hz", what plugin would I use and what would the parameters be set to? 1-band EQ?

[albee1952]

Use any EQ plugin that allows oyu to set a high-pass (or low-cut)filter and set it at 100HZ. If I am tracking seperate snare and tom mics, I am with Doc and will high-pass much higher.

[Bermaster]

What would the db be set to? How do I know how much to cut?

[Naagzh]

What would the db be set to? How do I know how much to cut?

It's obvious you're not understanding EQ. How much to cut? A high-pass filter cuts EVERYTHING below the frequency you specify. When you've engaged the high-pass filter on the EQ II plug (click the button with the high-pass filter symbol), the only parameter you'll be able to adjust is the cutoff frequency. There ain't no "db to set", dude.