Bookshelf Speaker Reviews

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 116.6 watts
1% distortion at 142.9 watts

Analog frequency response in Bypass mode:
–0.08 dB at 10 Hz; –0.02 dB at 20 Hz
–0.04 dB at 20 kHz; –0.21 dB at 50 kHz

Analog frequency response with signal processing:
–1.89 dB at 10 Hz; –0.60 dB at 20 Hz
+0.05dB at 20 kHz; –40.56 dB at 50 kHz

This graph shows that the SPA21's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 124.6 watts and 1% distortion at 147.2 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 230.3 watts and 1% distortion at 266.9 watts.

Response from the multichannel input to the speaker output measures –0.08 dB at 10 Hz, –0.02 dB at 20 Hz, –0.05 dB at 20 kHz, and –0.25 dB at 50 kHz. THD+N from the amplifier was less than 0.020% at 1 kHz when driving 2.83 volts into an 8-ohm load. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –65.46 dB left to right and –67.91 dB right to left. The signal-to-noise ratio with 2.83 volts driving an 8-ohm load from 10 Hz to 24 kHz with "A" weighting was –97.89 dBrA.

From the Dolby Digital input to the loudspeaker output, the left channel measures –0.01 dB at 20 Hz and +0.06 dB at 20 kHz. The center channel measures –0.02 dB at 20 Hz and +0.08 dB at 20 kHz, and the left surround channel measures –0.03 dB at 20 Hz and +0.05 dB at 20 kHz. From the Dolby Digital input to the line-level output, the LFE channel is –0.01 dB at 20 Hz when referenced to the level at 40 Hz and reaches the upper 3-dB down point at 109 Hz and the upper 6-dB down point at 117 Hz.—MJP