- Written by Chris Heinonen
- Published on 20 December 2010
On The Bench
At 6 dBV with a 1 kHz test tone, the Pioneer has 0.1% THD+N at 8 ohm, and it moves up to 0.12% with a 4 ohm load. We see a lot of even and odd harmonics as well, with the peaks measuring around 60 dBV below our test tone.
When I increase the power to 12 dBV, the 8 ohm number drops just slightly to 0.09%, but the 4 ohm load moves up to 0.17% THD+N, but keep in mind that the Pioneer isn't rated for continuous 4 ohm speakers. Many speakers rated at 8 ohm can drop down to 4 ohm at certain frequencies, however. The harmonics that were present before are here as well.
With a 10 kHz test tone, the numbers are far better than at 1 kHz, with 0.02% THD+N for 8 ohm with a 6 dBV load, and 0.04% for the 4 ohm load. Lower frequencies are typically harder to drive for an amplifier, which would account for the improved performance at 10 kHz. We also see a second order harmonic at 20 kHz for both that is over 70 dBV below the peak value.
Moving the voltage up to 15 dBV, the 8 ohm number moves up just slightly, as does the 4 ohm, once again showing that the higher frequency signal is easier for the amplifier to handle. Again we see a second order harmonic at 20 kHz for both that is over 70 dBV below the peak value.
With 19 kHz and 20 kHz tones, the IMD numbers for 4 ohm and 8 ohm loads are virtually identical. Our harmonics are again around 70 dBV below our test signals.
When we move up to 15 dBV from 6 dBV, the IMD numbers actually are reduced by a factor of 10, and the 4 ohm load measures better than the 8 ohm load in this case.
On the IMD test with 60 Hz and 7 kHz tones, the 8 ohm load measures slightly better, at 0.08% IMD compared to 0.1% IMD. We have a second order harmonic out at 14 kHz that is around 65 dBV below the fundamental value for both tests.
When we move up to 15 dBV, the IMD once again drops, but only by around 30% unlike with the 19 kHz and 20 kHz tones. The 8 ohm still measures better than the 4 ohm load, and the second order harmonic is once again present at around 65 dBV below the fundamentals.
Looking at the THD+N vs Frequency graphs, with a 12 dBV signal, both loads keep the THD+N below 0.2% across almost the entire frequency spectrum, with some odd peaks that jump above that on the 8 ohm load. The THD+N values trend downwards as you move higher in the frequency spectrum, once again showing that those higher frequencies are often easier for the amplifier to drive.