What Pure Cab actually does

    In the context of Pure Cab we are talking about trying to remove the phase type relationship that you get with a mic to make the sound more like an amp in the room.


    “As mentioned in the previous chapter, mic'ed guitar cabinets often have an unpleasant, “phasey” sound in the high- end frequencies – something you don’t get if you listen to a guitar cabinet directly, without a microphone. "Pure Cabinet" will gently polish the sound of the virtual (mic'ed) guitar cabinet to bring it closer the sound of the direct guitar cabinet. The fundamental character of the sound will still be maintained.” : From the manual.


    Whether it’s a Kemper profile or a mic’ed cabinet on a recording, it’s the same issue. That’s probably why lots of people hate pure cab and say you should never use it. Some commercial profilers “advise” turning it off to avoid screwing up the sound of their carefully captured profiles. (Personally I don’t mind it and leave it on at a low level most of the time but that’s just my personal preference). Many people would argue that pure cabinet doesn’t acheve the amp in the room effect it’s intended to. Others think it does. Therefore, my point was simply that I think it would be better to not introduce it (or something similar) at the profiling stage but simply capture the purest profile and add something like ure cab to tase afterwards.

    Quote from Wheresthedug

    In the context of Pure Cab we are talking about trying to remove the phase type relationship that you get with a mic to make the sound more like an amp in the room.


    “As mentioned in the previous chapter, mic'ed guitar cabinets often have an unpleasant, “phasey” sound in the high- end frequencies – something you don’t get if you listen to a guitar cabinet directly, without a microphone. "Pure Cabinet" will gently polish the sound of the virtual (mic'ed) guitar cabinet to bring it closer the sound of the direct guitar cabinet. The fundamental character of the sound will still be maintained.” : From the manual.

    That's the stated goal of Pure Cab, however from an EQ perspective, one practical benefit of the algorithm is that it helps to reduce or eliminate artifacts such as fizz, which in the case of a mic placed directly on (and in front of) the grill, is not the result of comb filtering or any other phase issue. The closer you get to the front of a cone, the more high frequency content that's incurred, thus more fizz. I used to notch out transients in the 5 KHz - 9KHz range by hand to eliminate fizz, and Pure Cab is great because it basically automates that process.

    Quote from Wheresthedug

    Whether it’s a Kemper profile or a mic’ed cabinet on a recording, it’s the same issue. That’s probably why lots of people hate pure cab and say you should never use it. Some commercial profilers “advise” turning it off to avoid screwing up the sound of their carefully captured profiles. (Personally I don’t mind it and leave it on at a low level most of the time but that’s just my personal preference). Many people would argue that pure cabinet doesn’t acheve the amp in the room effect it’s intended to. Others think it does. Therefore, my point was simply that I think it would be better to not introduce it (or something similar) at the profiling stage but simply capture the purest profile and add something like ure cab to tase afterwards.

    Well, if you want the full high end content of the cab in your recordings, turn it off. If you're like me and prefer a smoother top end (less fizz) then simply turn it on and set it as low as possible. I think it fails at emulating the cab in the room effect, but succeeds spectacularly at smoothing out the top end, which (for me) is a huge benefit. I can see a demand for such an algorithm at the tracking stage, primarily by those who desire the aforementioned effect.

    Rather than have Pure Cab baked into the profiling process, which I wouldn't necessarily want, you could turn on Pure Cab and capture an IR of the KPA's cab section, then import that IR into the KPA or any other IR loading software. The result would be an IR with Pure Cab baked in.

    Quote from Wheresthedug

    That makes sense but I still don't see the need when you can just turn pure cab on and off in any rig you want without baking it into anything. The end result is the same either way.

    I don't see the point of importing an IR with Pure Cab baked in back into the Kemper, however I can see the need for baking Pure Cab into an IR if you're interested in using it with another amp sim. For example, I've captured the cab section of some KPA profiles with (and for use in) the Axe-Fx, which allows me to save the amp and cab together as a single preset.

    One thing to point out. “Smoothing” the high frequency response doesn’t in fact act as a lo-pass, eliminating frequencies, it doesn’t even make the top end sound smoother, it’s just that it visually makes the frequency graph look smoother. It won’t “tame fizz”.


    Practically it means you get a more equal amount of every frequency up there! So e.g. you may actually get more odd harmonics and less even if the starting sound has an emphasis on even harmonics. The opposite way is also true.


    This might be why some people dislike its effects on the profiles they’re using it on, and others find it pleasing. It’s very profile dependent, or rather it’s very dependent on the harmonics the profile emphasizes as to what the outcome will be as it’s way up in harmonics territory rather than the original frequencies of the instrument. That’s probably why it’s only noticeable on distorted profiles.


    I don’t know enough about audio signal processing to say whether smooth frequency graph = phase aligned and wobbly = not. So I’m not sure about it improving phaseyness at the top end. To my ears it does sound a little like a comb filter.


    I think we just don’t know enough about what it’s doing, frequency response only tells us the outcome, not how it got there.

    Quote from Per

    “Smoothing” the high frequency response doesn’t in fact act as a lo-pass

    No, nor would I want it to. That's like using a machete to remove a splinter.

    Quote from Per
    It won’t “tame fizz”.

    Reducing the peaks may not eliminate fizz, but it can help to reduce it. Eliminating it depends on how much is present to begin with. As mentioned, I used to manually notch out the peaks with a PEQ. Pure Cab is a lot more efficient. One difference is that Pure Cab affects more than just the peaks associated with fizz.

    Back at you @Zapman. All is good, hope all is good in your neck of the woods.:)


    Sorry for the Off topic and certainly it's an interesting thread.


    It's amazing after all these years that Kemper is still the only Modeler that feels so close/closer to real tube amps.

    Edited 2 times, last by Dean_R ().

    I have Pure Cab turned off globally; but I can confirm with my ears what the OP showed. Just turning it on at 0.1, with certain high gain profiles, really helps smooth out some fizz in the high end. I’ve always just tried turning it on at minimum and back off; if it sounds good on, then I’ll sweep through and find my favorite setting. A lot of times it is between 0.1-0.5.


    I know it gets a lot of flac, but I’d rather have it and not use it, then to not have it at all.

    Ya know I'm the kind that reads into what I assume the majority has to say, and not nessesarily what I'm hearing. In most instances that would seem the logical thing to do, but sometimes its not correct. I may have to revisit pure cab.

    If you use FRFR the benefit of a merged profile is that the cabinet is totally separated in the profile.


    For my edification only... ;) Kemper/Axe-FX III/ Quad Cortex user

    I play a lot with pretty saturated profiles and for certain ones PC has been a life saver. The difference between a profile being a keeper or getting dumped in the trash in many cases - PC takes the edge off a lot of those "glassy" artifacts you can get when digging in. I don't remove it all since it's a big part of the tone. Just enough to keep it from being overbearing.


    One thing that also helps with this, and I stumbled across this by accident, is to add a small amount of 'space' to the rig (+2.0 in most cases) prior to adjusting the PC setting. I have zero data to back this up - just my ears. Tried it with 3 different pretty hot profiles from 3 different sources and got the same results each time. Also found that adding this amount globally doesn't seem to impact anything negatively which makes it easy.

    "I may not have gone where I intended to go, but I think I have ended up where I needed to be." - Douglas Adams

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