SREV1 Sampling Guide An Introduction to Impulse-response Sampling with the SREV1 Sampling Reverberator
1 Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 What is Sound Field Sampling? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is Convolution? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is an Impulse Response? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What are Impulse & TSP Signals? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 2 1 Introduction This document provides a basic explanation of sound-field sampling, and a tutorial by which you can actually sample a sound field and audition it on the SREV1. For more detailed information on the SREV1, IRSampler, or IREdit, please refer to the relevant documentation.
What is Sound Field Sampling? 3 As you can see from the following diagram, sound-field sampling consists of “firing” SREV1 test pulses into an acoustic space, thereby energizing the reverberation in that space, which is then picked up by a number of microphones and returned back to the SREV1 for processing. The acquired data can be saved onto PC Card, edited as necessary using IREdit, and then loaded into the SREV1 to create reverb programs.
What is Convolution? 4 What is Convolution? Convolution is a technique for imposing the characteristics of one signal onto another. What the SREV1 does is to convolve the reverberation characteristics of a previously sampled acoustic space (i.e., its impulse-response) onto another audio source, producing the same overall sound that would have been heard had the audio source actually been heard in that acoustic space.
What are Impulse & TSP Signals? 5 What are Impulse & TSP Signals? The SREV1 can generate two types of test signal. First we’ll take a look at the impulse signal. As explained earlier, an impulse has a very short playback duration and a flat response at all frequencies. You can acquire impulse-response data by using an impulse signal, but you can achieve a better S/N performance by using another type of signal, which we’ll talk about later.
What Equipment is Necessary? 6 What Equipment is Necessary? In order to perform sound-field sampling, you’ll need microphones and microphone preamps to pick up the sounds, speakers and power amps to output the test pulses, and the necessary connecting cables. Of course, you’ll need the SREV1, and depending on the type of I/O being used, you may also require A/D and D/A converters to get signals in and out of the SREV1.
Sampling Tutorial 7 2 Sampling Tutorial Assuming that you’ve set up your speakers and microphones and connected your PC to the SREV1 (see page 17 for hookup examples), you’re now ready to “fire” a few pulses and “grab” some samples. We’re assuming that SREV1 I/O is being taken care of by MY4-AD and MY4-DA cards. If you’re using external A/D and D/A converters, your IRSampler I/O assignments will need to be a little different to those specified later.
Configuring IRSampler 8 Sampler (Generator/Trigger window) Set Averaging to “8” Set the Sampling Time to “4500” msec (i.e.
Checking the Generator Output 9 Checking the Generator Output We’re now ready to check the generator output. Click the Start Generator button on the Sampling Control toolbar and verify that the test signal is being output properly from the speaker system. If it’s not, check the connections and generator output assignment. Starting with the level set low, gradually increase the power amp’s input attenuators so that the pulses can be clearly heard.
Using Your Data on the SREV1 10 Using Your Data on the SREV1 1 Put your data in the right folder The SREV1 can only load impulse-response data stored in the “c:\yamaha\srev\data” folder of the PC Card. So the first thing you need to do is to make a new folder called “data” in “x:\yamaha\srev\” and copy your acquired data into it, something you can do on your PC. (Note that “x” refers to the letter assigned to your PC Card while it’s inserted in your PC.
