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Topic: Best kind of input for sampling a hardware reverb

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  1. #1

    Question Best kind of input for sampling a hardware reverb

    I am trying to find out what the best way is to sample/record a digital hardware reverb. I have not yet done evaluations myself and wonder if a spike is better than a sweep. It's faster, that's sure.

    I have read that you do not have to deconvolve recordings when you use a spike and that the recording can be used as impulse. Is this true, or is it better to deconvolve or edit out the first spike ER?

    Maybe someone knows some good literature or sites on this subject (I already am a regular visitor of the NoiseVault forum ).

    Thanks in advance,

  2. #2

    Re: Best kind of input for sampling a hardware reverb

    I kept getting weird phasig issues, and eneralyl wasnt happy with the impulses when I used Spikes in my signal chain.

    I usd 12 second sweeps and higher to get what I was happy with, for the GOS impulses (ultimately te impulses didnt fully represent my signal chain, even when tweaking the predelays after the fact, it jsut sounded different....close, but different.
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  3. #3

    Re: Best kind of input for sampling a hardware reverb

    I think the ERs are the most important part, Peter! That's what tells you about the space, and my guess is it's what makes convolution so realistic.

    Altiverb has a sampling tool that generates sweeps.

  4. #4

    Re: Best kind of input for sampling a hardware reverb

    Hi,
    For what it's worth, I implemented Fast Convolution for Csound many years ago, and I remember testing it with a recording I made from my little Microverb II reverb unit. I used a narrow pulse, generated by an pulse generator - I was able to vary the pulse width. I experimented with the pulse width, making it as narrow as I possibly could, while maintaining an acceptable sound level in the output, and also while maintaining a *reasonably* consistent output from take to take. (if the pulse is too narrow, each take will vary quite a bit, and it's impossible to know which one is the "right" one to use. I just did this for experimental reasons, really, and I was over the moon with the results - it actually worked *very* well.

    Greg.

  5. #5

    Re: Best kind of input for sampling a hardware reverb

    Btw - I didn't have the know-how to do it any way other than use a spike, so I'm definitely not making any claims that it's the best. (my gut feel is that it could be the worst, from an accuracy and fidelity point of view). But it did produce very pleasing reverbs, to my ears. You definitely do not have to deconvolve the IR recordings from a spike - it's an impulse response already, so it's ready to be used for convolution. I didn't do any editing at all, either.

    Note that the delay between the dry and wet signals is important. This delay (initial period of silence) should be *included* in the impulse response which is used for the convolution, and would presumably vary for each reverb setting.

    Other than the swept tone method, there appears to be another method again - to use a repeating noise sequence:
    http://www.james-hopgood.net/Users/j...pulseResponses

    Greg.
    p.s I still have all the IR recordings I took from the Alesis Microverb, and can make them available upon request, FWIW. (assuming this doesn't encroach on copyright?)

  6. #6

    Re: Best kind of input for sampling a hardware reverb

    Also, I suppose a proper impulse waveform should really be used as the stimulus, rather than a simple square pulse. If the reverb unit has digital i/o,
    then it should be possible to get *very* accurate impulse responses if it's fed with an ideal impulse waveform (computed so it's frequency limited to half the sample rate) - I wonder whether this would produce as good a result as the other methods, then?

    Greg.

  7. #7
    hv
    Guest

    Re: Best kind of input for sampling a hardware reverb

    Quote Originally Posted by PeterRoos
    I am trying to find out what the best way is to sample/record a digital hardware reverb. I have not yet done evaluations myself and wonder if a spike is better than a sweep. It's faster, that's sure.
    Here's a link to a paper on the swept sine-wave approach:

    http://pcfarina.eng.unipr.it/Public/.../134-AES00.PDF

    I get the impression that sweeps solve problems capturing the response of spaces which aren't an issue with what you're doing.

    Howard

    EDIT- corrected link, hv

  8. #8

    Re: Best kind of input for sampling a hardware reverb

    I used a long sweep (8sec) with my Yamaha SREV-1 sampling reverb to capture the Lexicon 224XL, AMS RMX-16, Sony R7 and 777 library.

    The results were amazing. Almost impossible to distinguish from the originals.

    Only for reverse and gate reverbs I had to use spikes instead of sweeps.

  9. #9

    Re: Best kind of input for sampling a hardware reverb

    For the reverbs on which you used the long sweep method, did you also try the click method for any of them? If so, was there any noticable difference in the result?

    Cheers,
    Greg.

    Quote Originally Posted by northspeed
    I used a long sweep (8sec) with my Yamaha SREV-1 sampling reverb to capture the Lexicon 224XL, AMS RMX-16, Sony R7 and 777 library.

    The results were amazing. Almost impossible to distinguish from the originals.

    Only for reverse and gate reverbs I had to use spikes instead of sweeps.

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