Test Bench: Boston Acoustics Horizon Home Theater Speakers
In the lab
Frequency response (at 2 meters) front left/right 46 Hz to 18.2 kHz ±3.9 dB center 88 Hz to 20 kHz ±2.9 dB surround 76 Hz to 18.1 kHz ±2.9 dB subwoofer 23 Hz to 86 Hz ±1.9 dB Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right 90 dB center 89 dB surround 90 dB Impedance (minimum/nominal) front left/right 5.8/8 ohms center 7.1/10 ohms surround 3.6/8 ohms Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right 40 Hz at 91 dB center 80 Hz at 94 dB surround 80 Hz at 88 dB subwoofer 25 Hz at 97 dB SPL 105 dB average SPL from 25 to 62 Hz 109 dB maximum SPL at 62 Hz bandwidth uniformity 96%
All of the curves in the frequency-response graph are weighted to reflect how sound arrives at a listener's ears with normal speaker placement. The curve for the left/right front channels reflects response of the HS 460 with the speaker standing on the floor averaged over a ±30° window. The center-channel curve reflects response of the HS 225 averaged over ±45°, with double weight directly on-axis of the primary listener. The surround-channel curve shows the response of the HS 60 averaged over ±60°.
Because the HS 460 will always be used on a floor, all measurements were taken with the speaker on a floor. Both the center and surround channel speakers were measured on a 6-foot stand, which gives anechoic results to approximately 200 Hz. All upper channel measurements are taken at a full 2 meters, which emulates a typical listening distance, allows larger speakers to fully integrate acoustically and, unlike near-field measurements, fully includes front panel reflections and cabinet diffraction.
Tower, Center & Surrounds
All three upper channel speakers have a similar response shape above 1 kHz, with a moderate degree of smaller, unequalizable irregularities. The floorstanding HS 460 has a 3-dB floor bounce notch at 228 Hz, followed by a 4 dB peak centered at 400 Hz and a narrower 4 dB notch at 900 Hz. Bass Limits for all three are set by port noise, which is quite annoying for the center and surround systems; both should be sharply high passed above 62 Hz to avoid problems. The center channel doesn't develop off-axis lobing until the microphone is moved ±22.5° to either side, but it gets fairly severe at wider radiating angles.
The HPS 12HO Subwoofer bass limits were measured with it set to maximum bandwidth (Crossover Bypass and Flat trim) and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room users can expect 2 to 3 Hz deeper extension and up to 3 dB higher sound-pressure level (SPL.)
The HPS 12HO was moderately dynamic, but its bass limits are established by the subwoofer's protection circuitry, which allows a +3 dB SPL "blat" when the unit is driven by our test signal for two initial cycles at any test frequency. This can be audible on program material if subwoofer levels aren't carefully monitored during set-up.
Although the subwoofer crossover dial is marked from 40 to 180 Hz the actual acoustic range only covers 54 to 86 Hz. However there is only a marginal 2 dB of crossover/level control interaction top to bottom.