I just did a quick Google for Understanding EQ and the first thing to pop out was this http://www.soundonsound.com/sos/jul01/articles/equalisers1.asp which should give you somewhere to start.
Sound on Sound is a good magazine aimed at recording musicians in the main, and these guys talk a lot of sense usually. They also have a forum on their Web site here www.soundonsound.com
Re-posting your question in the Line 6 Lounge as already suggested should attract plenty of attention I would think
This was my fault for askng two questions in the same post.
The first post asking general EQ questions would make a good post in the general discussion area, but the second question definitely belongs in the support forum, and has been asked before... http://line6.com/community/message/207148#207148
Are there any good explanations of the built-in EQ models in the HD500? I've looked through the Advanced Guide, and to be honest generalized descriptions like "Low Mid" "Low Pass Q" and "Q" really don't provide very much information.
Have there been any information release notes explaining ANY specific information on what frequency information "Shift %" and "Q" percentages translates to?
Great question. Let me preface everything I say by: I'm no expert. My 10 year experience has only included: Zoom GFX-8 (2000?), Fender Twin red knob, Johnson JM60 modelling amp, Vox Tonelab SE (2009).
Everything just keeps getting better.
EQ is one of those mystical things that no one has a really good write up of but one of the best things to do is just MOVE THE KNOBS.
Eventually your brain can map out what does what, obviously the pros are way better at it too.
In terms of a clinical explanation, I don't know if there IS one, playing with the EQ is all dependent on the SOUND... since it's always different depending on speaker set up, room etc... it's difficult to nail down. The other problem is, there doesn't seem to be any good examples of "GOOD EQ". I wish there was something out there that said, HERE IS A GOOD SOUND, TRY TO GET THIS. That would make it so much more helpful... right now it's like trying to hit a target you can't see! What the heck is good sound?
RE your question about the highs: I read somewhere that as the volume gets louder, those treble frequencies start to really hurt your ears. So if you know you're going to be cranking it, you need to roll of those highs. Ice picks in ears. Just the way it is, different settings for different volumes.
You can look up a lot of those terms online... But a lot of them refer to the "shape" of the EQ curve...
For example, check out this site: http://mobile.jlaudio.com/support_pages.php?page_id=144
It really helps with graphs, but graphs don't necessarily translate to sound, so the best way is to just sit there and fiddle the knobs because these words won't translate to sound for you
Even though I have general idea of how to manipulate the sound curves graphically... without having a "sound" to aim for, it's challenging...
I have some info that might be helpful to you. Here are the actual values for frequencies that you're probably looking for:
MID Focus EQ
High Pass (HP) Frequency: 20 to 500 Hz
HP Q: 0 to 100%*
Low Pass (LP) Frequency: from 500 Hz to 18 kHz
LP Q: 0 to 100%*
Gain: 0 to 24 dB
Low (Low Pass Shelving Filter): -12 to +12 dB
Highs (High Pass Shelving Filter): -12 to +12 dB
Freq: from 45 Hz to 4.5 kHz
Q: 0 to 100%*
Gain: -12 to +12 dB
* Q is a ratio between the center frequency and the bandwidth, when bandwidth is the range of frequencies where the filter is attenuating (decreasing) the signal less than 3 dB.
Hope this helps.
Line6Perry -First off - Thanks for the response. It's greatly appreciated.
I understand what you're explaining, but this is the part I still don't understand (and I don't think I'm alone in this).
Let's say I want to use the parametric EQ, wanting to adjust the frequency between 3k and 4k. How can I do that, given the controls available?
1. I want to set the frequency I'm affecting, and I know that you've told me that the frequency goes from 45Hz to 4.5kHz. However, the only way I can adjust this is to use the FREQ knob, which only shows percentages. I have no way of knowing which percentage value will give me a center frequency of 3.5kHz for adjustment.
2. I realize that "Q is a ratio between the center frequency and the bandwidth, when bandwidth is the range of frequencies where the filter is attenuating (decreasing) the signal less than 3 dB", but how can I have any idea what frequencies that is actually affecting? The values are only given in percentages, so maybe if I spend an hour with a slide rule I can determine what that translates into regarding the 45Hz to 4.5kHz range, but wouldn't it be SO much easier if we could use actual frequency-range parameters to adjust?
3. In the LOWS settings "Low (Low Pass Shelving Filter): -12 to +12 dB" how can I use the controls I'm given to adjust the settings, if the parameters are only given in percentages? In other words, if I choose a setting of 65%, how the heck does that translate into a dB setting, and even if we're given some sort of translation table (which I know I would be VERY grateful for), wouldn't it be so much easier to be able to view the actual dB settings in HD500 Edit?
4. The same comments apply to the HIGHS and GAIN parameters. I have no idea what a gain setting of 40% means, because it's displayed in percentages instead of actual values.
Thanks again! I know you have to respond to numerous questions every week, so I appreciate your responses.
I'm sure Line 6 means well, probably trying to make it easier and less intimidating for folks who have no idea what a Hz is. But guess what, for those of us who do, it's kinda insulting. I can only speak for myself, but I feel like I'm being called stupid when I look at frequencies represented as percents. And what's worse, all the years I've spent learning how to dial good tones by memorizing what certain frequencies and other parameters related to audio signals do are worthless with the HD500. BTW "Q" is a filter quality factor and as such has no unit of measure, it's just a number that is usually adjustable through ranges like from 0.1 to 2.0 for instance. If Line 6 had gone with standard notation, those of us who know how a parametric bandpass filter sounds with a Q of 0.8 would have it a lot easier.
My opinion is, people who aren't tech-savvy or hate programming their units will stick to factory and downloaded patches anyway. People who already know this stuff have to play it by ear which isn't so bad but it's more time consuming than when you have a rough idea of where to start. People who want to learn their way around programming MFX units will learn how to program their POD HD, and whatever they learn will be useless for programming patches on other gear... or is this what Line 6 had in mind to begin with?
On of the biggest complaints I have with line 6 is the fact that they use only percentages with the parameters as opposed to what's actually being adjusted. This is true with EQ, which would be much easier to use with real world parameters. It's a little mind boggling since they use Hz for the speed control on Analog Chorus. Why not be consistent?