Measurement of speaker distortion

Usually we assume that speaker distortion is the highest distortion of all components of the audio chain. Therefore we assume amplifier distortion as unimportant, masked by speaker distortion. Aim of this short study was to measure distortion of a small monitor speaker with 2 x Beyma 5MP60N + 1 x Seas 27TDC-H1149 drivers.

In the 1st set of measurements 1102.5Hz sine tone from CD player was used, and CCIF IMD 19+20kHz twin tone from Philips test SACD. Voltage at speaker terminal was 0.6Vrms. Behringer ECM8000 microphone placed at 50cm distance from the front baffle, at the tweeter axis.

Measurement results at 0.6Vrms voltage, CD/SACD as a signal source

1. 1102.5Hz sine. THD = 0.2%

2. Twin tone 19+20kHz CCIF IMD. The result has surprised me a lot.

Measurement results at 2Vrms, sound card as a signal source

3. Distortion 2H, 3H and 5H components as a function of frequency

4. 5kHz sine

5. Twin tone 13+14kHz

Pavel Macura, 27.10.2009 and 30.10.2009