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Question about EQing

I have been noticing that when I high pass or low pass something it is boosting the db level while not actually sounding louder, Why is this?. I'm not boosting the Q so I don't get it. I'm using Logic's EQ by the way..

Thanks

I'm not familiar with that EQ, but does it have input and/or output levels? If so, are they set at +/-0dB?

quote:

Originally posted by cryophonik I'm not familiar with that EQ, but does it have input and/or output levels? If so, are they set at +/-0dB?

some of the new EQ's have autogain as well...

the cutoff freq of the EQ could be in the same area as the sound you are eqing, i notice this on bass tracks sometimes

noticed the same in reason. adding a cutoff freq then the track suddenly was clipping. were talking about o.1dB or something though.

Are you talking about frequency ringing? This is normal. Avoid it by using a less steeper cut.

Re: Question about EQing

quote:

Originally posted by lowski I have been noticing that when I high pass or low pass something it is boosting the db level while not actually sounding louder, Why is this?

I've read about this before, but haven't really noticed it myself. Is it boosting the level a lot? That is, is this causing a major problem in your mixing, or is it just an academic question?

As Anthony Ross says, some EQs have autogain, to allow you to hear the effects of EQing without level changes altering your perception.

"Frequency ringing"?. That might be it. I'll try using a less steeper cut, I've been trying out -48db per octave (setting on the EQ) on the lows. The only other suspect is auto gain becuase I'm not boosting any levels.

derail. Yes it can boost the levels by a few db sometimes which is way too high!!. Also yes, it's causing problems mixing

Also Kenny Rogers; I too have noticed an increased level when using the stereo imager's high solo in Reason.


As for the Eq I was using, it was the Channel EQ in Logic

Try bringing the Q down on the curve a touch also.

quote:

Originally posted by lowski "Frequency ringing"?. That might be it. I'll try using a less steeper cut, I've been trying out -48db per octave (setting on the EQ) on the lows.

That's your problem right there. Be careful when using such high slopes on bass. 48db on bass will surely introduce a lot of ringing and change the bass sound/tone. Try a linear phase eq and see if that helps. Btw, this happens with every eq so if it sounds good just leave it or stick a limiter after it. The overall volume is the same, just some peaks are causing the rise in levels.

yeah 4th order filter will boost a little just above the cutoff freq. 2nd order are supposed to not do this though so im shocked it does in reason as they are 12 and 6dB. closest example i could find:

vikernes,

The boost in gain is happening on more then just the bass. I just tried sweeping the low cut freq of a hihat and it boosted it 2db !!.

I used Loigc's defualt settings.
gain/slope: -24db/oct
Q: .71

Most of the time I'm using these cuts to get rid of inaudible high and low frequencies. The goal being to bring down the overall db level a bit, but I'm getting the opposite effect. I thought this technique was commanly used to keep unwanted frequencies from building up?. Am I going about this all wrong?.

screenshot!

This is a snare sample being trggered without the EQ's low cut on. As you can see the the selected channel maxes out at 0.0db



Now if I sweep the low cut across the level spikes to +3.1db

Do you have any other eqs available? Try with others, or post this snare sample here so we can try with different plugins and see how it goes. But it's normal, but 3db boost is a little odd I think - logic's eq probably has crappy filters.

Also, put a limiter on that snare. It probably won't affect the sound much (if at all), but will catch those overs.

quote:

Originally posted by lowski Most of the time I'm using these cuts to get rid of inaudible high and low frequencies. The goal being to bring down the overall db level a bit, but I'm getting the opposite effect. I thought this technique was commanly used to keep unwanted frequencies from building up?. Am I going about this all wrong?.

Try not to rely on this too much based on your own perception, as not only does prolonged listening diminish your perception of high frequencies, other people may be able to hear higher than where you decide to roll it off. A hi-hat might not even need it in most cases, while it is preferred on bass instrument and some mid instruments. Good monitoring is also very crucial, same with rolling off the bottom end. If you can't hear what you're doing, you may be doing more harm than good.

Re your original question, you could get a slight increase in gain around the passband (the Waves documentation had a really good explanation of this), but that you're getting a jump of 3 dB seems a bit much. Does it happen when EQing other channels too?

EDIT: Not sure if I got the definition of passband right, but I mean around the cut-off frequency.

EDIT 2: Why all the clipping?

DAW meters are quite inaccurate. The fact that you are cutting most of the energy ie the low end should guarantee a softer signal. It is for these reasons that you mix at -6 dbfs itb.

quote:

Originally posted by Mad for Brad DAW meters are quite inaccurate. The fact that you are cutting most of the energy ie the low end should guarantee a softer signal. It is for these reasons that you mix at -6 dbfs itb.

Not necessarily. At least as far as peak metering is concerned.
Using a steep low cut on a bass signal will almost always introduce ringing around the cutting freq. The higher the slope you use, the worse it is. And this is true for all eqs, some more others less.
I just tried a single square wave played at C1 and it peaked at -20.79.
Then I used the sonalksis eq set to high pass at 15Hz, 24db and while the sound hasn't changed (at least not enough to notice it instantly) the same square now peaked at -12.72. That's an impressive 8db "boost" yet I can not hear a single change in tone or loudness

Using the Fabfilter pro-q in the 'linear phase - maximum latency mode' at 48db per octave and low cutting at 10Hz the same signal peaked at -20.67. Again; no change in the actual sound. (btw, in 'zero latency mode' with the same settings it goes to -12db)

I haven't found a definitive explanation of why this is the way it is, but I've come across some people explaining this with freq ringing and lower signals phasing the higher ones out and stuff like that.

Now what's really interesting is that I didn't hear any change in the sound when doing this (both the high passed and the raw signal seemed equally loud to me - even though the metering showed an 8 db boost), so naturally I decided what would happen if I stick a limiter on there. Of course the raw signal went straight through without any limiting, but the high passed signal was indeed caught by the limiter and showed (roughly) 8db of limiting. And what's more important; the sound sounded like crap - like it was actually limiting 8db :\
And if you look at the waveform of a simple square while applying a low cut it actually changes form wtf? It actually starts to look like a saw wave while cutting at 15Hz which doesn't do anything and it still sounds exactly like the same square as when it wasn't high passed... lol

Talk about a WTF moment... I'm gonna have to ask around wtf is going on here.

So I did a lot of digging around the web reading all sorts of crap to further inform myself about eqs and basically I just wanted to know how on earth can low cutting at 10Hz introduce a 8db boost.

Finally I stumbled across a post by Holger Lagerfeldt that explains all of this. btw; this guy knows his shit. If you ever wonder onto gearsluts read only his posts, nothing else

quote:

Once in a while when mixing or mastering you will experience a situation where activating a HPF changes the peak level on the channel or master bus dramatically. This happens due to a particular "unlucky" phase change/delay. Phase changes are normal when equalizing, in fact that's how an equalizer works in the first place. But in this instance it could be annoying since the peak level changes so much. Large peak changes could cause overloads, cause dynamic plug-ins to pump, and eat up your headroom. Using a linear phase equalizer keeps the so-called group delays in control. The phase change that caused the peak to change dramatically before will no longer happen. In these cases you should think about switching to a linear phase equalizer. ... While I use hardware for equalizing in the mastering process, I often strike a balance. I might use a linear phase for the HPF and a minimum phase eq for the rest.

So it's nice to have a technical explanation of why this is the case. But I'm not sure this applies to OP's problem, because he's cutting at 600+Hz and a 3db boost from phase changing in that area is kinda odd I think.
And I've yet to figure out where (in my case) that 8db were going to for that matter. Because I can't see anything on an analyzer or the actual perceived volume, but it's eating away headroom like a pig. :\
Who knows, maybe you could gain a shitload of headroom if high passing everything with a lin eq?

quote:

Originally posted by vikernes Finally I stumbled across a post by Holger Lagerfeldt that explains all of this. btw; this guy knows his shit. If you ever wonder onto gearsluts read only his posts, nothing else

Thanks for that reply, vikernes. I was gonna say how a linear-phase EQ doesn't have this problem, but you bet me to it.

I think maybe everybody is overthinking the situation here and overlooking what is probably an obvious problem and/or a bug. Whenever I encounter something unexplainable like this, the first thing I'll often do is eliminate all of the other variables. Open the same audio file in a completely different project that is completely blank, other than the audio file in question. Insert the EQ as you did in the original file and use the exact same settings (i.e., save your existing settings from the original file as a preset). If you can't replicate the issue this way, then you've ruled out any frequency ringing phenomena, etc. and you can look elsewhere for a solution.

If you can replicate the issue that way, then you're probably looking at either a bug, or an actual phenomenon with the EQ setting (although I'm highly skeptical, given the actual readings that you're getting, which seem to suggest something far more amiss than frequency ringing). So, a next logical step would be to try to replicate the issue (in your new test project file) using a different EQ with the same settings. Remove the previous EQ from the project completely just to be sure that it can be eliminated as a variable.

I'd suggest starting there and seeing what kind of results you're getting.

quote:

Originally posted by cryophonik I think maybe everybody is overthinking the situation here and overlooking what is probably an obvious problem and/or a bug. Whenever I encounter something unexplainable like this, the first thing I'll often do is eliminate all of the other variables. Open the same audio file in a completely different project that is completely blank, other than the audio file in question. Insert the EQ as you did in the original file and use the exact same settings (i.e., save your existing settings from the original file as a preset). If you can't replicate the issue this way, then you've ruled out any frequency ringing phenomena, etc. and you can look elsewhere for a solution. If you can replicate the issue that way, then you're probably looking at either a bug, or an actual phenomenon with the EQ setting (although I'm highly skeptical, given the actual readings that you're getting, which seem to suggest something far more amiss than frequency ringing). So, a next logical step would be to try to replicate the issue (in your new test project file) using a different EQ with the same settings. Remove the previous EQ from the project completely just to be sure that it can be eliminated as a variable. I'd suggest starting there and seeing what kind of results you're getting.

Lowski would be interesing if you could this.

I just tried using Logic's Linear Phase EQ instead and it solves the problem, no more spikes. I read the manual and it says that the Linear Phase EQ can replaces the Channel EQ and the seetings will be the same. So I'll keep trying it out and let you know goes.

Thanks

it is quite obvious that logic's meters are not gauging the loudness of the channel in a way that translates visually. I'm not sure how it works but if it does not look at the entire spectrum and calculate a figure related to rms energy but rather just peaks, then yes, adding an EQ and cutting will introduce a slight increase in peak as this is how EQ's work at least digitally. This is why DAW meters are just bad all round. Good to know if you are clipping. That is about it. Even then, you could be clipping and your DAW won't realize it as it could just be for a certain amount of samples. Just mix at - 6 dBfs at 24 bit and stop worrying. There is no downside. It isn't a bug or anything you should be worrying about. Just mix less hot and allow yourself more headroom. It will make absolutely no difference in the final quality of the mix especially considering the type of music and the overall loudness it tends to have.

I'm not going to go through and talk about any indiidual post in this thread, because people are going to claim that I'm picking on them.

But for anyone reading, I wouldn't take any of the advice in this thread, because 80% of it is plain wrong, especially any mention of clipping, analogue vs digital, how EQs work, etc.

There are other threads on here about DAW meter resolution, inter sample peaks, etc. And I don't think there's any need to reprise that debate.

For what its worth, the finding that EQing with sharp slopes actually increases the level is not unusual or an anomaly. If I remember right, it occurs because of phase shift which is generated by all EQs (except linear phase ones) which cause reflections further on up the frequency spectrum. This effect is particularly noticable lower down the spectrum if I remember right. So doing any really vicious EQ work with any equaliser low down the spectrum will cause a lot of phase shift, and thus a lot of resonance, and thus an increase in level.

I'm don't design EQs for a living, so I recommend that anyone who's actually interested do some more research and get the facts. But the facts certainly aren't to be found here.

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