How do we do it?

About the test signal...

Measuring the room requires the use of test signals. In general there are three basic test signals that can be used. These are: noise, sine wave, or impulse. We have chosen to use a pseudo random noise (or p/n) signal for our measurements, which is a repeating, known source; unlike true random noise.

Noise Of the three signals, noise is the closest in character to theater sound. It has a known frequency response, which is determined mathematically. It allows the best measurement because noise can provide a large enough signal for quality measurements without distorting the audio system and it is much less susceptible to standing waves (nulls and reinforcements) than the alternatives. Using a digitally generated noise signal provides a totally repeatable set of accurate measurements. Sine A sine wave is simply a pure tone that is swept over the frequency response of the system typically 20 Hz to 20,000 Hz at a constant strength. A microphone (mic) measures how loud the signal is at the sitting position and the processor determines the signal strength of each band. This is a very simple approach but has the problem of reflections causing nulls and reinforcements which reduce the accuracy of the measurements. Inpulse The impulse method (ping) is done by generating a pulse with a very fast rise time and a very short duration. The shape of this pulse is modified by the audio system and room reflections which are measured and recorded. The signals are then analyzed by the use of a mathematical tool called a Fourier analysis to determine the characteristics of the audio system. This is theoretically straight forward but has the practical difficulty that when using signals low enough not to cause audio system distortion, obtaining enough energy over the entire frequency range to get accurate measurements is difficult.

Automatic EQ

The EQ 701 comes standard with a calibrated mic with stand. The mic is plugged into the front panel and is placed in the first listening position. The processor in the EQ 701 generates the test signals which are automatically adjusted to the proper level for the audio system. The processor cycles the test signals through all of the channels in turn, and are received by the mic. This process is repeated four more times for a total of five listening positions. The EQ processor then automatically determines the necessary corrections for each channel, and applies them. This entire process takes approximately 4 minutes of time. The corrections are held in the EQ’s memory permanently until a recalibration is needed such as: a change in furniture, decor or audio component occurs. The user can easily do this calibration and needs no special training or equipment, thus avoiding an expensive service call.

Finally, your system sounds right!

The processor in the EQ 701 automatically creates the corrections needed to remove the room effects. It does so by determining how to condition the signals so that they arrive at the listening position sounding like the moviemaker intended. No additional input is needed to make these corrections. In addition to the automatic corrections, there are user preference presets and selections; Like; more bass, treble etc. These are available from menus displayed on the front panel display.