Test Bench: Jamo Concert C 80 Series Home Theater Speaker System
In the lab
Frequency response (at 2 meters) front left/right: 34 Hz to 19.8 kHz ±4.7 dB center: 75 Hz to 18.1 kHz ±2.3 dB surround: 97 Hz to 4.3 kHz ±3.5 dB subwoofer: 27 to 195 Hz ±2.2 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right: 89 dB center: 87 dB surround: 85 dB
Impedance (minimum/nominal) front left/right: 2.8/12 ohms center: 4/12 ohms surround: 3.5/9 ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right: 25 Hz at 76 dB center: 40 Hz at 70 dB surround: 80 Hz at 87 dB subwoofer: 20 Hz at 89 dB SPL 104 dB average SPL from 25 to 62 Hz 107 dB maximum SPL at 62 Hz
All of the curves in the frequency-response graph are weighted to reflect how sound arrives at a listeners ears with normal speaker placement. The curve for the left/right front channel tower speaker reflects the C 807's response averaged over a ±30° window (the most typical listening angle) with the speaker standing on the floor. The center-channel curve reflects the C 80 Cen's response averaged over ±45°, with double weight directly on-axis of the primary listener. The surround-channel curve shows the C 80 Sur's response averaged over ±60°. I took the measurements for these speakers at a full 2 meters, ensuring that the effects of front-panel reflections and cabinet diffraction are included and that the outputs from all drivers are fully integrated acoustically.
TOWER, CENTER, & SURROUND The C 807's response suffers from the 6-dB floor-bounce notch at 250 Hz that often afflicts floorstanding speakers but exhibits no other significant spectral errors. This speaker also has unusually good low-frequency dynamic capability.
The C 80 Cen center channel showed flat response on axis, but our averaging techniques obscure the strong off-axis lobing common to many horizontally arrayed center-channel speakers. The dipolar C 80 Sur surround speaker has reduced high-frequency response because the tweeters are pointed away from listeners. This pattern is common, and usually considered an advantage, for dipolar surround speakers.
SUBWOOFER I measured the C 80 SUB subwoofer's bass limits 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 as much as 3 dB greater sound-pressure level (SPL).
The C 80 SUB has unusually good dynamic uniformity. It can deliver 104 dB or greater SPL in its primary 32- to 62-Hz operating range and will produce an honest 20 Hz at 89 dB within our 10% distortion limit at. The C 80 SUB also has excellent upper-frequency response (with usable output at 195 Hz), making it suitable for mating with even very small main speakers.
The sloping room-compensation setting reduces response below that 195-Hz limit by 4 to 5 dB per octave. The crossover control has most of its effect in the upper part of its rotation. Actual acoustical turnover at the 12-o'clock position is 46 Hz, and a marked 40 Hz on the knob results in a true crossover point of 55 Hz. Level is affected by 4 to 5 dB as crossover-frequency changes are made, so it's advisable to rebalance the subwoofer level control after making crossover adjustments.