Sunfire Ultimate II AV Receiver Measurements
All measurements were taken on the left channel. The Ultimate II's 2-channel analog frequency response, from the CD input to the speaker output in Source Direct mode, was –0.24dB at 10Hz, +0.05dB at 20Hz, -0.52dB at 20kHz, and -2.59dB at 50kHz. The response from the multichannel input to the speaker output measured –0.24dB at 10Hz, +0.05dB at 20Hz, -0.53dB at 20kHz, and -2.62dB at 50kHz.
The Dolby Digital frequency response (optical input to speaker output) measured +0.08dB at 20Hz and –0.62dB at 20kHz in the left channel, +0.13dB at 20Hz and –0.01dB at 20kHz in the center. With the left-surround channel set to "small" and the crossover frequency set to 80Hz, the highpass-filter response was –6dB at 61Hz, –3dB at 82Hz, and –0.39dB at 20kHz. The subwoofer line output, normalized to the response at 40Hz, was +0.46dB at 20Hz, -3dB at 67Hz, and –6dB at 81Hz.
The S/N (A-weighted, 2.83V into 8Ω) measured –95.1dB. Gain measured 28.8dB, CD in to speaker out, with an 8Ω load and the level control set to -18.5.
THD+noise in 2-channel operation at 2.83V into 8Ω measured 0.021% at 20Hz, 0.024% at 1kHz, and 0.019% at 20kHz. At 2.83V into 4Ω, the corresponding results were 0.028% at 20Hz, 0.036% at 1kHz, and 0.019% at 20kHz.
Driving all seven channels into 8Ω, the Ultimate II delivered 163Wpc at 20Hz and 173Wpc at 1kHz (to the nearest watt) before clipping (1% THD+noise). Into 4Ω, all seven channels operating, it delivered 141Wpc at 20Hz and 130Wpc at 1kHz.
With only two channels operating, at 1kHz, the Sunfire clipped at 276Wpc into 8Ω and 414Wpc into 4Ω.
The Sunfire puts out less power into a 4Ω load than into 8Ω, with all 7-channels driven. This is just the opposite of what we usually see. But this is not the case when it drives 2-channels. There is also a more dramatic difference than we usually measure in the 2- and 7-channel power results. This is likely due to the operating characteristics of Sunfire's tracking power supply.—TJN