Polar Plot (MDT-4000 Turntable)
This sequence measures the polar response of a loudspeaker in both the vertical and horizontal dimensions, designed to work with the Portland Tool & Die MDT-4000 turntable
Introduction
This sequence measures the polar response of a loudspeaker in both the vertical and horizontal dimensions. It is designed to work with the Portland Tool & Die MDT-4000 turntable, and has all the necessary commands to automatically rotate it via RS-232. The sequence uses a log sweep stimulus with the Time Selective Response algorithm so that the measurements can be run in a non-anechoic environment. Note that the time window needs to be adapted to the user’s measurement space.
The sequence plays the stimulus and measures at 10 degree increments from 0 to 180 degrees. This process is repeated with the speaker positioned horizontally. The two results are mirrored to display full 360 degree polar plots for each axis. A directivity index curve is also calculated for each axis and is displayed at the end of the test.
Required Hardware
- Audio Interface – Listen AudioConnect or similar
- Power Amp – Listen SCAmp or similar
- Reference Microphone – Listen SCM-4 or similar
- Portland Tool & Die MDT-4000 Turntable
Setup Diagram
Hardware Setup and Calibration
- Calibrate the amplifier as instructed in the SoundCheck manual.
- Calibrate the reference microphone as instructed in the SoundCheck manual.
- Connect output 1 of your audio interface to the input of the amplifier.
- Connect the output of the amplifier to your loudspeaker.
- Position your reference microphone at the desired test distance from the loudspeaker, and connect it to the microphone power supply.
- Connect the output of the mic supply to input 1 of your audio interface.
- Connect the RS-232 connection from your PC to the MDT-4000 turntable.
- Determine the turntable’s Com Port assignment and assign it in SoundCheck’s Hardware>External Devices Tab
- Open sequence step #11 (RS232 Read Integer) and select the turntable’s Com Port from the dropdown list
Get Sequence
Download Sequence (zip file)
Download Sequence documentation (PDF)
