Bookshelf Speaker Reviews

Analog frequency response in Quad Bypass mode:
–0.62 dB at 10 Hz; –0.20 dB at 20 Hz
–0.00 dB at 20 kHz; –54.14 dB at 50 kHz

Analog frequency response with signal processing:
–0.61 dB at 10 Hz; –0.20 dB at 20 Hz
–0.00 dB at 20 kHz; –54.14 dB at 50 kHz

The above chart shows the frequency response of the left (aqua), center (green), LFE (blue), and left surround (red) channels at the preamp outputs of the Dolby Digital decoder. The left channel measures –0.00 decibels at 20 hertz and –0.02 dB at 20 kilohertz. The center channel measures –0.00 dB at 20 Hz and +0.01 dB at 20 kHz, and the left surround channel measures –0.00 dB at 20 Hz and +0.05 dB at 20 kHz. The LFE channel, normalized to the level at 40 Hz, is –0.03 dB at 20 Hz, reaches the upper –3-dB point at 67 Hz and reaches the upper –6-dB point at 82 Hz.

Response from the multichannel input to the main output measures –0.04 dB at 10 Hz, –0.00 dB at 20 Hz, –0.04 dB at 20 kHz, and –0.27 dB at 50 kHz. The analog THD+N is less than 0.021 percent at

1 kHz with a 100-millivolt input and the volume control set to +2.5. Crosstalk with a 100-mV input was –71.55 dB left to right and –89.50 dB right to left. The signal-to-noise ratio with a 100-mV input from 10 Hz to 24 kHz with "A" weighting was –120.03 dBrA.—MJP

HT Labs Measures: ADA PTM-8150 Amplifier

All channels driven continuously into 8-ohm loads:
0.1% distortion at 119.2 watts
1% distortion at 138.8 watts

Frequency response:
–0.41 dB at 10 Hz; –0.11 dB at 20 Hz
+0.01 dB at 20 kHz; +0.04 dB at 50 kHz

This graph shows that the PTM-8150's left amplifier channel, with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 172.6 watts and 1 percent distortion at 187.7 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 235.5 watts and 1 percent distortion at 268.5 watts. With all channels driving 4-ohm loads, 0.1 percent distortion was reached at 165.7 watts and 1 percent distortion at 202.0 watts. An input level of 103.1 millivolts was required to produce an output of 2.83 volts into an 8-ohm load, indicating an overall gain of +28.79 decibels.

THD+N from the amplifier was less than 0.005 percent 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 –84.63 dB left to right and –84.60 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 –108.38 dBrA.—MJP