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TOPIC: Load convolution reverb in minisharc plugin?

Load convolution reverb in minisharc plugin? 9 months 1 week ago #39660

  • RyanC
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Hello all-

Does anyone know if you can load convolution reverb impulses in the minisharc plugin directly? I want to add a short, highly diffused, reverb to 2 outputs in my system. Typical reverb IR files are wavs. Can I just rename the extension to .bin?

I'm new to the OpenDRC platform and for the most part getting it and rephase figured out for my needs. I'm using it in a recording studio and one of the things I would like to play with is creating a fake ISDG return in a nearly anechoic environment- which is typically accomplished in large studios with the large rear wall diffuser and room geometry. The goal is to have as 2nd set of speakers dedicated to producing the 'ambient room' signal, which will be delayed so it arrives at the listening position about 25ms after the primary signal. This should not be purely a specular reflection of the original, but highly diffused with maybe a .5 s reverberant tail. I will use the presets on the DA8 to switch it on and off.

It may make more sense to find an algorithmic reverb box to do this ultimately, but I like the idea of being able to try a lot of different IRs to see what would work best.

Thanks for any input!
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Load convolution reverb in minisharc plugin? 9 months 4 days ago #39725

  • alandbush
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You will need the program Sox to convert wav to bin to be compatible with the MiniDSP. Sox will also convert the sample rate to be compatible.
However, I do not know if Sox can generate the correct number of coefficient taps.
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Load convolution reverb in minisharc plugin? 9 months 2 days ago #39791

  • Richard
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Yes, you can load any impulse you like, such as a reverb, but remember...

The longest possible impulse of all 6144 taps at 48kHz sample rate is only 128 milliseconds length - that would be very short for a typical reverb tail.

While 128 milliseconds is plenty for most loudspeaker impulse corrections, or linear phase EQ, or room impulse correction, or even a guitar cabinet speaker modelling impulse, or maybe some ambience / early reflection type impulses, however a typical church hall reverb tail might be several seconds of decay(!) which is far longer convolution time duration than possible here.

You can calculate the impulse duration length as number of taps / sample rate.
eg. for OpenDRC: 6144 taps / 48,000 Hz = 0.128 seconds.
So if you wanted 0.5 second reverb tail (500 ms) that would therefore be requiring 24,000 taps (samples) duration at 48kHz which is I'm afraid way beyond the 6144 taps limit that's available from OpenDRC. (To convolve that length impulse you would need something like a dedicated hardware convolution reverb (eg. Sony DRE-S777 or Logidy EPSI ) or run computer software convolution.)

For stereo reverb, you'll need to have discrete LEFT and RIGHT channel mono impulses uploaded separately, but that's fairly simple task.

To convert your ".wav" file into a ".bin" file that the OpenDRC machine will recognise, observe these basic rules...

1.) Each WAV file must be mono, 32 bit float, 48kHz sample rate, 128 ms duration (6144 sample length maximum)

2.) The file format you need to save into must be "headerless Raw PCM data" with the data format "32-bit IEEE (0.24) normalized float (type 3 - 32-bit)" type (and, if asked, "Offset input data = 0") which as raw PCM data, should give you the file extension ".bin" or ".pcm" which you can then manually rename to ".bin"

3.) These mono ".bin" files with these exact settings should produce files of 24Kb in size (exactly 24,576 bytes if you do right-click > Properties) so if your resulting ".bin" files are different size to this, maybe you accidentally saved a stereo wav or another sample rate, bit depth or duration, so beware that likely is wrong format which OpenDRC won't upload. (Technically you could upload shorter duration impulses, for less than maximum 6144 taps, but probably you'll always want to use the maximum 6144 length that's available.)

4.) If you wish to re-open these ".bin" files back into your DAW, you typically need to re-specify these same format settings again whenever it tries to load raw files it asks you to choose a format, sample rate, bit depth, etc., so the DAW knows how to interpret the headerless raw data. You can probably use most common DAW to convert between ".wav" and ".pcm" / ".bin" files, if they can save raw pcm data they should work.
Last Edit: 9 months 2 days ago by Richard.
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