The Onkyo TX-SR804's overall performance was fairly typical of mid-range receivers today, which is to say astonishingly good in most respects: Noise, distortion, and frequency response were generally very good.
The receiver's software-selectable impedance switch strictly limited output in the 4-ohm position to about 60 to 65 watts. At the 6-ohm setting, however, it drove 4-ohm loads to high power in 1- and 2-channel operation, with no discernible ill effects. On our difficult (and admittedly not real-world) 5-channels driven test, the TX-SR804's current-limiting protection circuitry kicked in within 2 to 3 seconds at any level above 55 watts per channel - not an unusual result for a mid-priced receiver.
I noted some behaviors related to crossover operation not mentioned in Onkyo's user manual. First, the response of the multichannel analog inputs cuts off sharply above about 21 kHz in all modes including Direct (or "Pure Audio"), effectively negating any benefits (however questionable or elusive they might be) of ultrasonic output from formats such as DVD-Audio or SACD. (Direct mode does turn off bass management on these inputs, which otherwise is active in the same fashion as for digital inputs.) I was not able to test response with a multichannel PCM input. Also, the response of any high-passed ("Small") channels fell away very sharply below about 40 Hz, which could have blend/phase implications for setups in which unusually low crossover settings are selected.
DOLBY DIGITAL PERFORMANCE
All data were obtained from various test DVDs using 16-bit dithered test 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 -3. All level trims were at zero; except for subwoofer-related tests, 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: 151/224* watts (21.8/23.5 dBW)
5 channels driven (8 ohms): 56** watts (17.5 dBW)**
6 channels driven (8 ohms): not tested
Distortion at 1 watt (THD+N, 1 kHz)
8/4 ohms: 0.03/0.04%
Noise level (A-weighted): -74.9 dB
Excess noise (with sine tone)
16-bit (EN16): 1.6 dB
Frequency response: 20 Hz to 20 kHz +0.1, -0.3 dB
*Speaker-impedance setup switch at "6-ohm" position. With switch set to "4-ohm," output was limited to about 64 watts (18 dBW) in all power tests.
**Receiver's protection circuits automatically current-limited after 2-3 seconds operation at any level above about 55 watts (17.4 dBW).
MULTICHANNEL PERFORMANCE, ANALOG INPUT
Reference input and output level is 200 mV; volume setting for reference output level was -3 dB.
Distortion (THD+N, 1 kHz, 8 ohms): 0.03%
Noise level (A-weighted): -86.2 dB
Frequency response: <10 Hz to 21 kHz +0, -3 dB
STEREO PERFORMANCE, DIGITAL INPUT
Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was -3.
Output at clipping (1 kHz, 8/4 ohms, both channels driven): 133/60 watts (21.2/17.8 dBW)*
Distortion at reference level: 0.03%
Linearity error (at -90 dBFS): 0.1 dB
Noise level (A-weighted): -75.3 dB
with 96-kHz/24-bit signals: -85.1 dB
Excess noise (with/without sine tone)
16-bit (EN16): 2.0/2.9 dB
quasi-20-bit (EN20): 17.5/18.0 dB
Noise modulation: 0.6 dB
Frequency response: 20 Hz to 20 kHz +0, -0.3 dB
with 96-kHz/24-bit signals: 20 Hz to 46 kHz +0, -3 dB
*Speaker-impedance setup switch at "6-ohm" position. With switch set to "4-ohm," output was limited to about 60 watts (17.8 dBW) in all power tests.
Measured results obtained with Dolby Digital test signals.
Subwoofer-output frequency response (crossover set to 80 Hz): -24 dB/octave 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): 7.5 volts
Subwoofer output distortion (from 6-channel, 30-Hz, 0-dBFS signal; subwoofer trim set to 0): 0.04%
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" (if C=small, LR also must be "small")
Speaker-distance compensation: available for all main channels
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