I've come to expect stellar bench results from high-echelon Onkyos (and lower-echelon ones, too, usually), and I got them. Noise and distortion measurements were uniformly state of the art. Frequency response was excellent as well, though the TX-SR875 exhibited a very small rolloff, of about 0.5 dB per octave, above about 10 kHz in all playback modes. (In other words, flat to 10 kHz and about 0.5 dB down at 20 kHz.) Not really significant, and if truth be told, probably more boon than bane with most real-world program material.
Power results were generous almost to a fault, handily exceeding the receiver's 140 watts-per-channel rating in all tests except for seven-channel-simultaneous power, which came very, very close. The TX-SR875 got quite hot under prolonged power testing, however. And the fan (which came on only under severe stress) was a bit noisy, though users should never hear it while playing at the volume required to activate it. With the receiver's impedance menu set to "4 ohms," power in all modes was limited to around 55 watts, as is usual with such current-limiting modes. All our listed tests, including 4-ohm power measurements, reflect performance with the "6 ohms" setting. Bridged output at clipping was in excess of 300 watts, two channels driven into 8 ohms.
DOLBY DIGITAL PERFORMANCE
All data were obtained using various test DVDs with 16-bit dithered signals, which set limits on measured distortion and noise performance. Reference input level is -20 dBFS, and reference output is 1 watt into 8 ohms. Volume setting for reference level was -7.5. All level trims were at zero, except for subwoofer-related tests, and all speakers were set to "large," subwoofer on. All are worst-case figures where applicable.
Output at clipping (1 kHz into 8/4 ohms)
1 channel driven: 201/322 watts (23/25.1 dBW)
5 channels driven (8 ohms): 141 watts (21.5 dBW)
7 channels driven (8 ohms): 128 watts (21.1 dBW)
Distortion at 1 watt (THD+N, 1 kHz)
8/4 ohms: 0.02/0.03%
Noise level (A-weighted): -76.1 dB
Excess noise (with sine tone)
16-bit (EN16): 0.7 dB
Frequency response: 20 Hz to 20 kHz +0, -0.8 dB
MULTICHANNEL PERFORMANCE, ANALOG INPUT
Reference input and output level is 200 mV; volume setting for reference output level was -14.0.
Distortion (THD+N, 1 kHz, 8 ohms): 0.01%
Noise level (A-weighted.): -82.9 dB
Frequency response: <10 Hz to 183 kHz +0, -3 dB
STEREO PERFORMANCE, DIGITAL INPUT
Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was 6.5.
Output at clipping (1 kHz, both channels driven)
8/4 ohms: 185/320 watts (22.7/25.1 dBW)
Distortion at reference level: 0.02%
Linearity error (at -90 dBFS): 0.2 dB
Noise level (A-weighted): -75.6 dB
with 96-kHz/24-bit signals: -88.8 dB
Excess noise (with/without sine tone)
16-bit (EN16): 0.3/0.3 dB
quasi-20-bit (EN20): 9.6/9.9 dB
Noise modulation: 0.2 dB
Frequency response: <10 Hz to 20 kHz +0, -0.8 dB
with 96-kHz/24-bit signals: <10 Hz to 44.5 kHz +0, -1.7 dB
Measured results obtained with Dolby Digital test signals.
Subwoofer-output frequency response (crossover set to 80 Hz): 21 dB/octave (approx.) above -6-dB rolloff point of 80 Hz
High-pass filter frequency response (crossover set to 80 Hz): 12 dB/octave below -3-dB rolloff point of 80 Hz
Maximum unclipped subwoofer output (trim at 0): 7.4 volts
Subwoofer distortion (from six-channel, 30-Hz, 0-dBFS signal; subwoofer trim set to 0): 0.02%
Crossover consistency: bass crossover frequency and slope were consistent for all sources and formats
Signal-format consistency: consistent for all applicable formats
Speaker size selection: all channels can be set to "small"
Speaker-distance compensation: available for all main channels
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