Can I convert self-shot 500ms 44.1KHz/24 Bit IRs to other lengths/sample rates?

Discussion in 'Digital & Modeling Gear' started by RiF, Jun 17, 2019.

  1. RiF

    RiF Member

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    I am currently creating a bunch of cabinet impulse responses of my various cabs, speakers and mics. As of now, I am using a 500ms sweep and I am recording at 44.1KHz/24 Bit.
    While these work great in software convolution plugins like MixIR for example, different devices (Helix, AxeFx, Two Notes C.A.B., ...) support different IR-lengths/sample rates/bit depths.

    As I am planning to release these IRs for free, I am searching for a solution that hopefully does not involve creating those different formats by shooting an IR mutiple times with different sweeps and at different sample rates / bit depths.

    Any thoughts on how to create and provide cabinet IRs that are compatible with as many devices as possible? Can I just record at 500ms/96KHz/24 Bit and then convert them down to other formats?
     
  2. Rewolf

    Rewolf Member

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    Not an expert, but my understanding is that yes you can convert like any other audio file. Most hardware seems to use 48k 16bit as a standard, but HX Edit for example will convert the files when loading so you don't need to worry about it too much.

    The only thing that I am wondering is why you are doing only a 1/2 second sweep - I would have thought that a more accurate picture would be captured with 5 seconds?
     
  3. cliffc8488

    cliffc8488 Member

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    Voxengo makes a free SRC app IIRC.

    As for sweep length the length of the sweep determines SNR. For near-field IRs a short sweep delivers plenty of SNR because the mic is so close to the source (inverse square law and all that).
     
  4. Lele

    Lele Member

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    You can "create" IR (not record IR, you need a software to make the IR, but I guess you already know this) at 96kHz/24bits and then convert them down, no problem at all.
     
  5. RiF

    RiF Member

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    Yes, right. I am recording the sweep (@44.1/24) and then I am creating the IR by using a deconvolution software.
     
  6. RiF

    RiF Member

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    What about the length? Can I just truncate a 500ms file or do I need to use both a 200ms and a 500ms sweep to create IRs with both lengths?
     
  7. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    AFAIK, most modelers will adjust accordingly.
     
  8. Chocol8

    Chocol8 Member

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    Open in a daw and chop.
     
  9. Lele

    Lele Member

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    Except for Fractal devices that I don't know anything about, all the other multi-fx will cut the IR lenght to something shorter than 50 ms, so imho you could even truncate the files after 50 ms...
    Even better than "truncation" is the "windowing" (in simple words: reducing the amplitude progressively instead of truncation but according to some specific methods) but in that case you should make the exact files for each multi-fx; on the other hand maybe (just maybe) while you load the IRs in the multi-fx this truncation/windowing is already done by the software you use to load the IR inside the multi-fx so it is not helpful to make it earlier.

    Software convolution (VST plug-ins for example) on the contrary could use longer IRs (longer than 50 ms) even if the contribution to a proper cab/mic reproduction is very questionable (because of the effect of early reflections).
    But this matter belongs to other very good specific posts.
     
    RiF likes this.

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