Meambobbo EQ Graphs

[TBone55]

As a newbie on to how to use EQ effects I am very grateful to Meambobbo for his terrific guide on how the POD HD EQ effects actually work and have a question regarding the values shown in the different EQ graphs. For example, looking at the Graphic EQ graph response graph for the 80hz frequency, With the gain set at 0db, the output level for this frequency is approximately -20db. My interpretation of this would be that at 0db of gain, the 80hz frequency is operating at a negative gain output of -20db. The signal is in otherwords, being attentuated by 20db. Looking at all the other graphs for this particular EQ as well as the other EQ effects, it looks to me like none of them actually have a positive output but rather, just a less negative output as the gain is increased. I guess I'm a little confused at just how the gain and the output actually relate to each since the output is always a negative number it seems, even at maximum gain values. 

 

Hope this isn't too dumb of a question.

 

Thanks.

 

P.S.  A big thanks to all the others that have contributed to this EQ topic. I'm starting to find out what a big difference using some of EQ effects can make in helping me to dial in different tones. 

 

 

[TBone55]

Thanks. I forgot about that. You're right, pfSmith0 did provide those graphs. I've also seen the video by Matt explaining those pesky EQ effects that are in %. I've tried to talk to Line 6 about why they did this and if they would look at providing an update at least for the HD Edit software but I haven't had any luck. They just keep referring me to the forum. It's a shame because my POD HD500X is without a doubt the best unit out there for the money.

 

Ciao Paisan!

[mcbeddall]

Hi could you point me in the direction of those eq videos please?

I'm using a firehawk but a video or 2 about the eq would be a help

Thanks

[jandrio]

[pfsmith0]

Hi, the graphs don't show gain per se, as in 0 dB mean gain =1. This is because the input is in volts (dBV) while the output is in fullscale (dBFS). The units of measure are different. Rather, I adjusted the input level until I got a -20dBFS signal for a blank, default signal chain. The output of a filter set to 0dB would then be -20dBFS. The graphs show the output level in dBFS, not gain. Check the units of the Y-axis. It's the absolute signal level in dBFS, not gain in dB.

 

But, if I were to to do this again I would convert it all to dB as I think that would be more useful. Basically add 20 dB to everything and call it dB.

 

Gosh, this is harder to describe clearly than I thought...

[TBone55]

Thanks pfsmith0, I'll look at the graphs again now that you've explained the measurements. Just to clarify then, the units in db that are to the right of the graph are really dbV input? Sincerely appreciate the great information you've provided, especially for someone like me who knows little about how EQ's work. I guess I'm from the simpler era where the tone knobs on the amp told you everything you needed to know (or at least you thought they did). 

 

Great Work!

[mcbeddall]

Thanks for posting the video , very interesting, I find the eq the hardest to dial in without having the spectrum analyser to look at for reference, it's a 4 band semi parametric eq on the firehawk and fortunately the parameters are in dB and hz so it's not total guesswork

 

Is there any rule of thumb when cutting highs and lows to remove harshness?

Like do you have a starting point for your high shelf? I'm guessing maybe start at 5k and bring it down until I hear the tone slightly too dark and then edge it back a bit?

I'm pretty new to eq so don't assume I know stuff if you can help

(Just a quick background on why I'm so interested in the eq, I'm using the firehawk and couldn't be happier with the tone through headphones, all my patches are exactly where I want them sound wise, however when I run into my lt3 speaker for rehearsals it sounds very harsh or boomy or both, I was hoping if I cut the highs and lows with eq I might get lucky and find a setting for the eq that works across all my patches, is that realistic or is it likely to be very different for each patch)

Thanks

[pfsmith0]

No, the numbers to the right are the EQ settings in dB as dialed in on the HD500. The numbers to the left are the output level obtained in dBFS. Using the Graphic EQ for example, when I set it to 0dB I got -20dBFS output (because I'm inputting a signal that is -20dBFS). For this EQ, the gain is accurate. At 0dB, -20dBFS input give a -20dBFS output. Gain = 0dB. Gains for the other EQs are:

 

Graphic EQ: 0dB gain setting = 0dB gain

Vintage Pre: 50% gain setting & 75% output setting  = 0dB gain

Mid-Focus EQ: 12% gain setting= 0dB gain

Studio EQ: 4.6dB gain setting = 0dB gain

Parametric EQ: 50% gain setting = -3dB gain

4 Band Shift EQ: 0dB setting = -3dB gain

Q filter: hard to tell exactly but if you set mix = 0% then 0% gain setting = -3dB gain

 

Note that for Global EQ, which I measured much later (since this feature was added much later), I actually DID measure true gain. At mid-settings it has a gain of -15dBFS/V. That is, a 0dBV input signal will give a -15dBFS output signal. 

[TBone55]

Thanks Again pfsmith0, Your help is greatly appreciated.

 

:D