Question about shelving EQ...

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RAMI

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When I use a shelf on 250hz (for example) and cut it by 3db, am I cutting EVERYTHING under 250hz by 3db? Or am I cutting by 3db at 250hz, and then it tapers off until it's cutting only maybe 1db down at 60hz or whatever?
Thanx in advance.
 
In a low shelf, the size of the cut increases the lower you go. So if it was -3db, everything below would be cut by even more.

In a high shelf, the same is true, for everything higher than the frequency the shelf is applied to.

If I'm wrong, then parametric EQ's are just designed really stupid.
 
Ah, it increases, not decreases...I had it backwards. Thanx alot!
 
Mistral said:
In a low shelf, the size of the cut increases the lower you go. So if it was -3db, everything below would be cut by even more.

In a high shelf, the same is true, for everything higher than the frequency the shelf is applied to.

If I'm wrong, then parametric EQ's are just designed really stupid.
Click to expand...
Not on a shelf. It begins a slope area at or around the set freq, drops or raises everything below that equally.
Rami, you're describing a peak/dip. :)
--Oops, I meant this part is peak/dip. '...Or am I cutting by 3db at 250hz, and then it tapers off until it's cutting only maybe 1db down at 60hz or whatever?'

Wayne
 
Yup...think shelf hanging on the wall...your guitar pick collection on top...lower the shelf, all the picks on the come down unless of course, if you don't have a level and you tilt the shelf but then, all the picks would fall to the floor. :D
 
I can't tell if you guys finally got it straightened out or not. :D So just to clarify:

A shelf response goes up or down for a while then levels off.

A low-pass or high-pass rolls off continuously at 6 or 12 dB per octave, though the rolloff can be even steeper.

Some equalizers have a Q adjustment for these curves, and that adds a peak in the response just before the rolloff.

Many EQ plug-ins show the response in a graph as you change the various settings, so that's a great way to learn what each filter type does.

--Ethan
 
OK, so now we're back at square one. Ethan doesn't seem to agree with you guys that a shelf is flat all the way. I really don't know who's right. But I do have to say that when I look at a shelf EQ in software, it does seem to taper off, visually.
 
Mistral said:
In a low shelf, the size of the cut increases the lower you go. So if it was -3db, everything below would be cut by even more.

In a high shelf, the same is true, for everything higher than the frequency the shelf is applied to.

If I'm wrong, then parametric EQ's are just designed really stupid.
Click to expand...
You are wrong. What you are describing is a high pass (or low cut) filter where everything below a certain frequency gets quieter the farther down you go.

A low shelf lowers everything below the set frequency the same number of db.

A parametric EQ is the peak/dip thing that mixsit describes.
 
RAMI said:
OK, so now we're back at square one. Ethan doesn't seem to agree with you guys that a shelf is flat all the way. I really don't know who's right. But I do have to say that when I look at a shelf EQ in software, it does seem to taper off, visually.
Click to expand...
Ethan is right, you are just misunderstanding what he is saying. Look at your software EQ, set the low shelf for 1k, now lower the gain. You will see that there is a slope, then it levels off. That is why it is a shelf

With a low cut (or high pass), you will see the slope just keep going into the dirt.
 
Oh yes, I misunderstood what was meant by "levels off". I get it now, it's as I thought...thanx alot.
 
Farview has it right, and so did Ethan.

Almost no transitions in frequency filtering happen immediately; there are no black and white cutoff points, there is always a slope in the transition.

While not super-accurate in it's graphic depictions, the attached screen shot of part of the control panel for the Neodynium plug in gives a good comparitive representation of the different types of EQ filters.

Note that low or high shelfs (just like low or high pass filters) can also boost, and not just cut. But whether it's boosting or cutting, it is boosting or cutting all frequencies below (low shelf) or above (high shelf) the set frequency by equal amounts one the transition slope has kicked in.

G.
 

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Thanx alot, guys. I misunderstood what was well explained, and the "shelf" analogy is very good. I guess that's why they don't call it a cliff.
 
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