Profiling (or modelling?) cabs without mics

  • Okay, I don't know if this feature request makes sense or if it's possible, but I'll try to explain:
    The Kemper can make a perfect reproduction of a miced cab. That's great for recordings, or for big stages where the stage monitors will play the miced amp.
    But for bedroom players, rehearsals, or small stages without FOH, it doesn't really make sense to hear a miced amp.
    The other problem is that the mics used for profiling and their placement will have a huge effect on the final profile. Go to the rig exchange and try different profiles of a same amp, a Fender Deluxe for example. All these profiles will sound completely different, (some better than others, but this is subjective) but none of them will sound like the real amp (in your room).


    Now the new 3.0 firmware is a big improvement to me as it can give a true representation of the amp head. But you are still limited by your own real cab if you're using a real cab and power amp (you get the "amp in your room tone" but you don't have the flexiblity of FRFR), or by the miced merged cab if you're using FRFR.


    Hence my (kind of) feature request; it would be great to have a true representation of the real cab without any mic trace.
    I don't know if that's possible, but with Mr CK, you never know...
    What do you guys think?

  • If you are using a linear cab and want to hear the real profiled cab, there's no other way that using a mic, since the cab by its definition moves air: the only device able to "feel" a cab is something that can perceive moved air, such as a mic... or an ear :)


    The only way to minimize the effect of mic'ing over capturing a cab is to use a flat mic (for example a test mic) and avoid the early reflections, as Jay Mitchell has explained in one of his posts.
    IOW, the mic'ing changes the sound of a cab because it's not flat and because you place it so that what it picks up is very different from what our ear picks up.


    HTH :)


  • Hence my (kind of) feature request; it would be great to have a true representation of the real cab without any mic trace.


    Hmm... Recording the cab in an anechoic chamber with a lab-reference mic would do it.


    The approach used by Antares' mic modeling plugin involves telling the plugin what the source microphone being used is, applying an inverse transform to get a mic-less approximation and then optionally applying the IR of a different mic to that. You can post-process prerecorded guitar tracks using this method today, although the very idea of taking the mic out of the picture begs the question of what part of the speaker is being, ahem, "non-miked" !




    -djh

  • An anechoic chamber would not be needed actually. It's enough to kill the early reflections.


    Here follow some quotations from Jay Mitchell. If you search TGP you'll come across much more stuff :)


  • I believe the original question involved the hypothetical of taking the microphone out of the picture, viabcroce. As has been mentioned elsewhere, the Kemper's cab profile is a time-averaged representation of the spectrum profile of the system as a whole, with the room's reflections and reverb tails contributing to the overall EQ as perceived by the mic from (potentially) all directions as limited by its polar pattern & off-axis response.


    So, worst case: If you were to mic a guitar cabinet in a long-decay concrete reverb chamber with an omni - even a lab-reference one - the EQ characteristics of the room's reverb buildup would indeed contribute to the cab profile, unless special measures were taken. (And by "special measures" I'm thinking of maximum-length-sequence (MLSSA) DSP techniques which can break down under conditions of heavy ambient noise. If that technique was being used by the Kemper, the test tones would reveal it)


    So yes, if you want to be pure about it - anechoic chambers.

    Edited 3 times, last by dhodgson ().

  • I believe the original question involved the hypothetical of taking the microphone out of the picture, viabcroce.
    So yes, if you want to be pure about it - anechoic chambers.


    I'm of course not as an expert as Mr. Mitchell is on the matter. But as I got it, if you avoid the early reflections (talking about an IR) you just get what the cone is transmitting straight to the (measuement) mic. Later reflections will be late to the party, hence my "you would not need an anechoic chamber".


    :)