Help with converting Kemper Cab to IR

    Greetings! I’ve been experimenting with using other units and using both the Kemper and other said units. There’s a particular profile (It’s a merged profile) That I would love to have as an IR. It’s quite the amazing cab/mic setup. I want to follow this method: How to extract/reconstruct Profiler cabinet IRs

    But I just don’t have the right hardware/computing power to handle it. Is there an easier way to accomplish this? If not would somebody possibly be willing to do this process with the profile? I would be willing to throw a few dollars your way if so! Thanks

    Edited 2 times, last by TDW03PW ().

    There are a few ways to convert the CAB:


    1. The method you mention above sends an IMPULSE thru the Kemper and you record what comes out the other side.
    2. You download ROOM EQ WIZARD and you do a frequency sweep of the CAB and convert that sweep into an IR.


    Both methods work but require some software and knowledge to get thru.

    Room EQ Wizard (REW) is the easier method.


    REW METHOD

    1. Connect the Kemper input and outputs to your sound card.

    SC Out -> Kemper In
    Kemper Out -> SC In
    2. Open REW and in preferences select the correct Inputs/Outputs. Close the dialog.
    3. Click MEASURE on main menu and Continue anyway if asked about calibration.
    4. Click START.

    5. After the sweep is done you will be shown the freq response of the CAB. Select EXPORT IMPULSE RESPONSE AS WAV.


    You now have the IR, however, it is not in a usable format. You need to do some editing.


    1. Download GOLDWAVE audio editor or use the editor of your choice.

    2. Open the WAV file and trim off the extra space around the IR. You will want the IR to be a little bigger than 2048 samples.


    STUFF TO KNOW

    1. You may want your sound card in the correct mode that you want the IR to be in. ie 44.1 kHz or 48 kHz. The Kemper is always in 44.1 I believe, so you should be there already. This is not 100% necessary as you can pick the sampling rate in REW when you export.


    2. IRs are 1024 or 2048 samples long. You want the IR to start as soon as possible or you are adding LAG. So manually editing the IR is your best bet.

    At 44.1kHz you will want a minimum of (1024/44.1)=23.22 mS of audio for 1024 samples.

    At 44.1kHz you will want a minimum of (2048/44.1)= 46.44mS of audio for 2048 samples.


    3. You can play around in REW to see if you can set it up to trim off the extra space around the IR. There are some settings to try. But some times the IR will have oscillations before the actual pulse that you may want to trim off. And if you edit it manually you will learn what is going on more.


    4. Normalize the IR. This means make the IR as loud as possible. This can be done in REW when you export or in your audio editor.

    IRs are normally a large peaking pulse followed by oscillations. If you edit the IR and the phase gets destroyed, the IR may lose its peaky pulse and become a blob of oscillations. If normalized this blob will be 3-6 dB louder than the original IR.


    5. Once you have the IR in wave format, you can apply some EQ to it if needed. Depending on the EQ code being used, you may destroy the phase response of the IR. So your milage may vary.


    6. Some IRs are louder than others.

    The entire IR is multiplied times every sample of your guitar playing. IRs that adjust low freqs will have a large negative spike right after the large positive spike. This negative spike will make the IR quieter since you are removing some of the overall volume. That is completely normal and part of how it is supposed to work.



    EXPERIMENT

    You now have the means to measure IRs for anything. Speakers, other units, etc. In fact I wrote a program to let me draw the freq response and then I use REW to convert it to an IR (need to generate minimum phase response first).


    For speakers just use a microphone instead of the Kemper Out -> SC In.


    I got a cheap Chinese class D amp off Amazon and I have swept ALL of my speakers. Seeing the REW freq response will also teach you about proper micing techniques. Since you will see bad resonances and suck outs from the room, other speakers, etc.


    EXAMPLE FREQUENCY SWEEP

    Your Kemper sweep should look like this. The RED line is the freq response. The GREEN line is the phase. The phase normally has an instant change at the speakers resonance. Usually around 75 Hz for 12" speakers. The phase should not change phase everywhere. Normally around 75Hz and then again at a higher freq. If your micing technique is bad, there will be phase changes all over the place and the freq will have large dips as well.


    You dont need to know any of this for the IR conversion. Just hints to let you know you are the right track.


    IR EXAMPLE

    1. The image on the left is what an IR test pulse is. A single sample at full loudness in a WAVE file.

    2. Once that pulse goes thru your Kemper, you get a smoothed out oscillating thing (Right image).

    3. If you dont trim off the beginning of the IR (PINK) you are adding lag and altering the low freq response of the IR.

    I think I can do it for you easily. I have acoustical measurement software that actually measures and creates IRs. I measured my own cabinets that way. I just tested my kemper measuring only the CAB and the measurement looks correct.
    So, if you want to send me your profile, I'd be happy to send you the IR of the cab.

    Quote from Jonelli

    So, if you want to send me your profile, I'd be happy to send you the IR of the cab.

    This is the 3rd and super easy method. 8)


    Since the person making the IR can deal with the specifics like turning off the AMP, pedals, etc to get the true CAB response. And be aware that the final IR may sound different since what you hear on the Kemper may include EQs from pedals, amp model, etc.


    Jonelli Which software are you using?

    I have SysTune, Smaart, and EASERA.

    I'd be using SysTune for this. I have verified that the "all-off" response of the kemper is pretty much flat everything and any filtering is below or above 20/20K, so the CAB-only button on appears good as an IR.

    Quote from TDW03PW

    Thank you both very much! @RosboneMako Your response was great! I feel much more confident on being able to do IRs. I feel like that was a full blown lesson on them!

    The Kemper was my first experience with IRs and I went down a rabbit hole for a year or so just bathing in IR possibilities. So I am no expert, I just have a lot of experience messing with them in not so normal ways :)

    Best of luck on your adventures!