Digital Filter Building/Playback Process

Major Steps:

The following steps are processed automatically by the program.  At the end of each step, the program stops so you can review the results and decide whether to stop or continue.  The process takes < 15 minutes per speaker side.  All drivers are wired as they will eventually play so the soundcard, amps, and wiring are all measured/corrected by the process.

After the digital filter building process is completed, you restart the program and select "Play CD Wav" or "Play Analog In" and the digital filters are used to play the music.  Digital CD .wav files in a directory are up sampled in real-time to 88.2kHz and then the digital crossover filters are applied.  For the "Play Analog In" operation, the data is sampled at 88.2kHz/24 bit and then the digital filters are applied for each driver.

You can change the filter set or size in real time and replay a portion of a cut for comparison purposes simply by moving the time slider back in time.  There are woofer and tweeter level adjustments and also a woofer phase adjustment.

• Measure Midrange Magnitude and Phase
• Build Midrange Digital Crossover Filter - (Both Scan-Speak and SEAS)
• Measure Tweeter Magnitude and Phase
• Build Tweeter Digital Crossover Filter - (Both Scan-Speak and SEAS)
• Measure Phase at Midrange/Tweeter Crossover Frequency
• Adjust Tweeter Filter Phase
• Measure Tweeter/Midrange Level
• Adjust Midrange Filter Level
• Measure Woofer Magnitude and Phase
• Build Woofer Digital Crossover Filter
• Measure Phase at Woofer/Midrange Crossover Frequency
• Adjust Woofer Filter Phase
• Measure Woofer/Midrange Level
• Adjust Woofer Filter Level
• Measure Woofer/Midrange/Tweeter Levels
• Adjust Midrange Filter Level 2
• Adjust Woofer Filter Level 2 - Final Speaker Level Adjustments
• Polar Response Measurement - 0, 15, 30, 45, 60 degrees horizontal

Window and Graph Color Definitions:

• All Digital Filters are FIR of Length 16K.
• Magnitude is 1/3 Octave Smoothed and Phase is 1/10 Octave Smoothed.
• Major dB Divisions are 3dB, Minor are 1dB.

Top Window = Freq Response Window

• Light Red = Original Driver Magnitude Response
• Light Green = Original Phase Response

• Purple = Target Response Desired - two curves - one magnitude, one phase
• Yellow = Magnitude Correction to be applied to get Target Response
• Blue = Phase Correction to be applied to get Target Response

• Bright Red = Corrected Driver Magnitude Response
• Bright Green = Corrected Phase Response

Bottom Window = Time Domain Response Window

• Green = Original Impulse Response or Sine at Crossover Freq
• Yellow = Correction Filter
• Red = Corrected Impulse Response or Sine at Crossover Freq

06/27/02