- Written by John E. Johnson, Jr.
- Published on 03 June 2010
On the Bench
Distortion measurements were made within an 80 kHz bandwidth. I used XLR connections throughout. Instead of an 8 ohm power resistor as the load, I used one of my Carver Amazing Mark IV speakers. So, the load for the first four graphs shown below was an actual speaker (the THD+N vs. Power Output and Frequency Response measurements were made into an 8 ohm power resistor). This is something new I am experimenting with, and the results are enlightening.
At 1 kHz, THD+N was a scant 0.002%.
IMD was also very low, at 0.001%.
19 kHz and 20 kHz test tones resulted in only two side bands near the fundamentals. This is excellent performance.
The THD+N vs. Frequency test resulted in an almost flat distortion curve all the way out to 50 kHz.
Here is the Impedance/Phase graph for the Carver Amazing Mark IV speaker. Note the low impedance and - 600 phase in the 3 kHz to 8 kHz range. This is a combination of impedance and phase that would be a challenge for an amplifier, and there is a small peak in the distortion curve (the graph above) at 8 kHz. Still, the curve is nearly flat, which represents superb performance.
Power output showed its first knee at 18 watts with an 8 ohm load, and 30 watts with a 4 ohm load. The second knee occurred at 620 watts and 850 watts respectively, before the rapid rise to clipping (1% THD+N) at 750 watts and 950 watts respectively.
The measured frequency response was down 3 dB at 100 kHz.