I doubt there is a problem. There are many ways to implement a LPF. I wouldn't stress over it. Recognize there is a difference, which you have, and use the one you like the best.
LPF has frequency, slope and Q. Some cut gently around 6db per octave other very aggressively like 48db per octave and some are in between. This is not a fault just a design decision. I think the Kemper used to b 1st order (6db) but was updated to 2nd order (12db) a few version back. 2nd order seems to be a good default for guitar.
LPF has frequency, slope and Q. Some cut gently around 6db per octave other very aggressively like 48db per octave and some are in between. This is not a fault just a design decision. I think the Kemper used to b 1st order (6db) but was updated to 2nd order (12db) a few version back. 2nd order seems to be a good default for guitar.
To try and help, an octave is a doubling of frequency.
A 6dB filter at 6500 means that 13 kHz will be 6 dB quieter than 6.5 kHz.
A 12dB filter at 6500 means that 13 kHz will be 12 dB quieter than 6.5 kHz.
The term ORDER generically refers to how many electrical components (capacitor/inductor) are used in the filter. So a filters cost would go up with order. In the digital domain, that cost is how much time the CPU needs to calculate the filter.
As Wherethedug is saying, the Kemper tries to use the ORDER that sounds the best for a guitar.
A typical 12" V30 speaker could have a built in Low Pass Filter with cutoff around 3 kHz that rolls off around 20 dB per Octave (20 dB/Oct).
The speaker roll off is based on the inductance of the voice coil and the mechanical physics of trying to move a large object at high speeds.
As Dug was saying a filter has a lot of other parameters like Q. This means a low pass filter is usually designed to be rolling off 3 dB by its cutoff spec. So a 6500 Hz LPF may be down by 3 dB already at that frequency. But that is getting real picky and digging into the details too much.
What's best to use depends on the skill of the sound man. If he has no experience he might just leave everything flat to where it would make sense to give him a more mix-friendly signal. If he has medium experience he might do certain things EQ wise by default without using his ears. If he has high skill he might like your tweaks and not double up on them because he IS using his ears. In all these situations, listen yourself as best you can to the house mix and communicate as much as possible.
Especially if the person is skilled, don't discount the effect of how your guitar sounds to you in your IEM's as that can affect how you play. Personally, my playing diminishes when I don't like my sound. In this case, I can count on the sound man to, say, use a HP filter and perhaps boost a certain frequency that helps it cut. But in my in-ears, I have myself loudest and those same tweaks make my guitar sound thin and shrill because they are purposefully on top of the mix.
Lets say you have a Hi Cut set to 4 kHz (Fc, Corner Frequency, Frequency Cutoff). In most cases at 4k you will be cutting the signal by 3 dB. If you add another filter at the same cutoff, 4 kHz, you will be cutting another 3 dB of signal. Meaning at 4k you are now 6 dB down.
Since 4 kHz is our cutoff, that is where the filter is starting to work. So you are only losing approx 3 dB. By 12 kHz it could be cutting 20 dB. Adding another filter cuts another 20 dB. So signals at 12 kHz are now 40 dB quieter. 40 dB is about as much dynamic range as a cassette tape can reproduce. Meaning it is almost inaudible to you it is so quiet.
So a HiCut does not stop ALL frequencies at that point. It gradually decreases their volume as the frequency goes up from the cutoff. How fast it cuts off depends on the filter. Most are generically designed for about 20 dB/Decade. But they can be made as steep as you want. 200 dB/Decade?
When you pick a string, there is a sharp rise in voltage. A spike if you will. That spike can only rise fast if there is no filter, because the faster it rises, the higher the frequency it is. Adding a HiCut filter will slow down how fast that pick attack can be. And creates a smoother and softer rise.
Roll the tone knob on your guitar and that is the effect of adding a HiCut filter (tone knob). Less high frequency and less pick attack.
Filters will also change the phase of the signal as the frequency changes. So if you mix a filtered signal with an unfiltered signal, you may get weird phase effects as the signals cancel each other out. This is generically how a PHASER effect works. Not what you want if you want clear transparent audio.
So..just revisiting this not so old thread...why does adding a lpf on the digital mixer on top of the kemper eq with the same lpf parameters modifies the sound?
They sum to each other, as Mako explains.
The question is, mutatis mutandis, the same as asking why we'd ever need a linear cabinet to reproduce a sound that cuts say at 6 kHz: if you used a cab that cuts at 6 kHz itself you'd have a double cut (or triple, depending on the filter's slope).
so let's just say that if i need 2 eq's with one of them having a low cut and high cut and the other one beeing flat on those regions, does it cancels one another?
a flat EQ has no influence. To cancel you need to apply the same amount of attenuation and boost to the same frequency.
so let's just say that if i need 2 eq's with one of them having a low cut and high cut and the other one beeing flat on those regions, does it cancels one another?
You have to reason in terms of algebraic sum: 0 dB (flat) + -6 dB = -6 dB
HTH
