Niles StageFront Home Theater Speaker System Test Bench
In the Lab
Frequency response (at 2 meters) front left/right 75 Hz to 12.7 kHz ±6.9 dB center 75 Hz to 14.4 kHz ±4.5 dB wall surround 77 Hz to 114.7 kHz ±7.0 dB back surround 87 Hz to 3.5 kHz ±3.1 dB subwoofer 32 Hz to 100 Hz ±2.8 dB Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right/center 88 dB wall surround (dipole) 90 dB back surround (bipole) 83 dB Impedance (minimum/nominal) front left/right/center 3.9/10 ohms wall surround 3.6/8 ohms back surround 3.2/5 ohms Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right/center 50 Hz at 78 dB wall surround 50 Hz at 77 dB back surround 80 Hz at 85 dB subwoofer 20 Hz at 89 dB SPL 113 dB average SPL from 25 to 62 Hz 119 dB maximum SPL at 40 Hz bandwidth uniformity 95%
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 PRO2870 LCR with the pod mounted for satellite use and averaged over a ±30° window. The center-channel curve reflects response of the pod mounted for center channel use and averaged over ±45°, with double weight directly on-axis of the primary listener. The wall surround-channel curve shows the response of the IW770FX mounted in a wall and averaged over ±60°. The response of the PRO770FX back surround was simply averaged over ±60°.
The left/right, center and back surround 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.
The PRO2870 LCR, when used as a left/right channel, has a downward sloping bass-to-treble balance as frequency increases, with measurements showing output dropping off by roughly 1 dB-per-octave and a fairly wide depression between 800 and 3000 Hz. It also has pronounced off-axis lobing centered at 1.3 kHz, most likely due to the horizontally arrayed woofer/pod. The Pod level control has roughly the +/- 1 dB effect as specified, but the Treble and Midrange controls have less than half the marked +/- 3 dB effect. The Boundary Compensation control cuts output below 230 Hz by an ultimate 4 dB. When arrayed as a center channel, the speaker has no off-axis lobing at listening angles narrower than ±30°.
The primary surround IW770FX, when measured as a dipole, has a 5-db elevation at 100-200 Hz followed by relatively moderate narrow irregularities at higher frequencies. Interestingly, a null, usually considered part of the usefulness of a dipole speaker, only occurs when the speaker is switched to "Bipole" mode. The PRO770FX on-wall speaker, when measured as a dipole, does show the classic dipole mid-frequency notch along with reduced high frequency output. The "Diffuse Sound Level" control did not appear to have any significant effect on the sound being emitted from either surround speaker.
The PRO12 SW subwoofer's bass limits were measured with it set to maximum bandwidth 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).
Superb dynamic capability is this sub's primary calling card. It does 90 dB SPL at 20 Hz as measured from 2 meters and will produce 115 dB SPL or more at any frequency above 25 Hz. However, although the crossover control is marked up to 120 Hz, the system's upper bandwidth only extends to 100 Hz when measured in its Movie setting, and the level drops by 5 dB as the crossover control is turned downward to 40 Hz. Switching to Music mode only reduces the output by 1.6 dB, with no change in frequency response.