What Pure Cab actually does

    Based on posts here and TGP, it seems many people have a less than positive opinion of Pure Cab. While I didn't intentionally set out to analyze what Pure Cab does to the frequency response, I just happened to look at a spectrum analyzer while adjusting Pure Cab and noticed something interesting. Here's what the frequency response looks like with and without it:


    Without Pure Cab:


    With Pure Cab:


    In the first image, you can clearly see several peaks and valleys with Pure Cab disabled. However, with it set to just 0.1, those dips and peaks smooth out considerably. In a nutshell, that's what Pure Cab does, and in my opinion that's a good thing if your use case is recording, as the peaks and valleys often manifest as fizz and/or some other high end anomaly that isn't necessarily pleasing to the ear.


    At its lowest setting Pure Cab does a good job of smoothing out and rounding off the high end in gainier profiles.

    I'd like to add that Pure Cab is an adaptive algorithm designed to remove artifacts created by close mic'ing.

    Adaptive meaning that it is on the lookout for such artifacts, but if there aren't any, it won't change the sound.

    So it's function isn't 'smooth out everything over 10k' or so, it is much smarter than that.

    Quote from DonPetersen

    I's loke to add that Pure Cab is an adaptive algorithm designed to remove artifacts created by close mic'ing.

    Adaptive meaning that it is on the lookout for such artifacts, but if there aren't any, it won't change the sound.

    So it's function isn't 'smooth out everything over 10k' or so, it is much smarter than that.

    No question it's adaptive, and I understand the goal of Pure Cab. The effect is empirically verifiable using a spectrum analyzer in conjunction with certain gainier profiles. The higher the setting, the greater the affected range. From an EQ perspective, the effect appears as a smoothing with respect to dips and valleys in the high end of the spectrum at low settings. This was observed using numerous profiles, and most clean profiles were unaffected.

    Quote from DonPetersen

    I'd like to add that Pure Cab is an adaptive algorithm designed to remove artifacts created by close mic'ing.

    Adaptive meaning that it is on the lookout for such artifacts, but if there aren't any, it won't change the sound.

    So it's function isn't 'smooth out everything over 10k' or so, it is much smarter than that.

    Sounds like exactly the algorithm I was wishing for when close miking a JCM 900 set to stun in the pre-Kemper days. There was occasionally a battle with some fizziness on the top end. It sounds like this would be a good tool to have in the bag should I encounter that sort of behavior with profiles that exhibit similar characteristics.

    Kemper remote -> Powered toaster -> Yamaha DXR-10

    Quote from Awesome_Elvis

    Would there be some way to have a pure cab-like effect in the profiling process?

    Why would you want this? It would then be baked into the profile and unable to be adjusted or bypassed. With the current method you have the option.


    I think it might all become pretty academic shortly with the new Kemper Kone functionality anyway. If the NAMM videos are anything to go by that’s going to be pure cab on steroids :)

    Quote from Wheresthedug

    Why would you want this? It would then be baked into the profile and unable to be adjusted or bypassed. With the current method you have the option.


    I think it might all become pretty academic shortly with the new Kemper Kone functionality anyway. If the NAMM videos are anything to go by that’s going to be pure cab on steroids :)

    To ditch any artifacts from close mics and other magic ?

    Quote from Wheresthedug

    :D


    But i don’t think the arifacts are actually a result of the close micing itself only how we perceive the sound in an open space after the micing. Therefore, the apporpiate place to do any adjustment would seem to be in playback racther than creation but I could be totally wrong - wouldn’t be the first time :S

    If artifacts are only a matter of how we perceive sound in an open space after miking, how are we able to see artifacts such as fizz with a spectrum analyzer when close miking and not so much when room miking?

    My (limited) understanding is that the "artifacts" which appear on the analyzer are the result of phase cancellations. Surely for phase cancellations you need a minimum of two sources to be out of phase with each other. A close mic has a single source right in front of it so what is the other source that create the artifacts?


    It's at times like this I REALLY miss Monkey_Man knowledge and clarity of explanation. :(

    Quote from Wheresthedug

    My (limited) understanding is that the "artifacts" which appear on the analyzer are the result of phase cancellations. Surely for phase cancellations you need a minimum of two sources to be out of phase with each other. A close mic has a single source right in front of it so what is the other source that create the artifacts?


    It's at times like this I REALLY miss Monkey_Man knowledge and clarity of explanation. :(

    The two sources can be the direct signal (shortest path from speaker to mic) as one, and the sound being reflected from eg. the floor can be the second source. So a single mic situation can certainly have the same or similar phase issues (specifically here comb filtering).


    Yes, MM is missed :(

    So surely that mean that the mic is picking up the natural signal which happens to be bright (fizzy) which isn't an "artifact". That would make the smoother Room mic the "artifact" as it isn't getting the full signal directly and the sound which reaches it therefore has some element of comb filtering in it from the reflections.

    Quote from Wheresthedug

    So surely that mean that the mic is picking up the natural signal which happens to be bright (fizzy) which isn't an "artifact". That would make the smoother Room mic the "artifact" as it isn't getting the full signal directly and the sound which reaches it therefore has some element of comb filtering in it from the reflections.

    "Artifact" has several meanings, one of them being a defect(ie. an imperfection, shortcoming). Fizz falls into that category for many people. Listen to room miked cabs and you'll generally hear a lack of fizz, which is as expected given the distance of the mic from the amp. Bottom line is, when using a single close mic, fizz isn't the result of comb filtering.