Freesound Forums

I have written GVerb, an open source free reverberator. It could
be better. I would need impulse response (IR) samples of quality
reverbs. The IRs found for the convolution reverberators fails
for my use. I need examples of early echoes (ambiance) with
diffusion and density set to minimum, and the tail reverberation
set off.

I also have a plan which would make this sampling project more
useful for people who use the convolution reverbs.

Juhana

hello juhana,

There's a lot of recording people on this site, but very few with very in depth knowledge about dsp processing. Perhaps it would be wise to point people to either a HOWTO or a tutorial on how to record IR's, and why they are useful/used.

- bram

Actually, I know only how to record IRs useful for my development work.
The mono input sample would be a bell shaped waveform with width
of a few samples. That sample is then fed to the reverberator, to left,
to right, or to both channels.

As what comes to setting the reverb: I planned to download the manuals
of reverbs and check details from there. I already have manuals for
Lexicon, Roland, etc. reverbs.

I have observed that some IRs for convolution reverbs seems to
be generated by using a square waveform. I don't understand
the use of quare pulse. Do they sound good, I don't know.

In any case, if anyone has a quality reverb, we work toward IR set
which is useful for all of us. That may mean a set of 100+ (or more)
IRs per algorithm. Is sampling of reverbs illegal?

Juhana

I guess that they use square pulses because they contain high frequency components (fundamental plus odd harmonics 3rd, 5th etc). This then gives a good signal which can then be used to check the performance of their reverb algorithms

I have experience in creating Impulse Responses for different reverb units. The two best ways to go about this is 1. Record a loudspeaker playing back a single sample fully normalized. You then record the room as it plays back the single sample. You then have the impulse response. I have also seen people use a starter pistol instead of a loudspeaker playing back a loud single click. 2. The second way of recording a good IR is to play a sine wave frequency sweep through a good studio monitor with a flat frequency response. This method works good if you use audioease's impulse response pre processor which takes out the frequency sweep from the sample and leaves you with only the IR. Most of the IR's I have recorded are not directly owned by me so I can't give you those, but I may be able to find some others that I have done that can be used.

- Eric