Mission Cyrus 782 loudspeaker Measurements
Sidebar 2: Measurements
Starting with the Listening Environment Diagnostic Recording (LEDR) on the Chesky Test CD, I found the 782s did quite well on the "Up" test, the most difficult for a loudspeaker. The image clearly moved up from the loudspeaker, but flattened at the top into a "J" shape. Ceiling reflections could account for this, however. The "Over" test was similarly good, the 782s producing a solid "rainbow"-shaped image path between the two loudspeakers. The third LEDR test, "Lateral," was handled well by the 782s. They created precise, well-defined images at all points between the loudspeakers. (Incidentally, I highly recommend this recording for evaluating and tweaking your listening room and for achieving optimum loudspeaker placement.)
Driving the 782s with a variable-frequency sinewave oscillator revealed that the 782's enclosure is remarkably inert and well-damped. I could detect only one frequency340Hzwhere the cabinet vibration became audible. Below this frequency, no cabinet resonances could be felt or heard. This is excellent performance.
Looking at fig.1, the 782's impedance magnitude (solid line) and phase angle (dotted line), we can see the sealed-box tuning with the impedance peak at 65Hz. The impedance is fairly low through most of the spectrum, dropping below four ohms in the upper bass. An amplifier with the ability to drive current into lowish impedances is therefore recommended.
Fig.1 Mission Cyrus 782, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)
Fig.2 shows the 782's FFT-derived anechoic frequency response spatially averaged over a 30° lateral window on the tweeter axis. The nearfield woofer response, measured with the Audio Precision System One and appended to the MLSSA data, is plotted to the graph's left-hand side. The response is fairly flat, but with a rise in upper-octave energy and some midrange anomalies at 5 and 7kHz. Notice also the droop in extreme treble. From the auditioning, I would have predicted a smoother curve than this. However, the Mission stands placed my ears 6" above the tweeter axis, which could account for a smoother treble perception during the auditioning.
Fig.2 Mission Cyrus 782, anechoic response on tweeter axis at 50" without grille, averaged across 30° horizontal window and corrected for microphone response, with nearfield woofer response plotted below 200Hz.
Moving to the time domain, the 782's impulse response is shown in fig.3. The fact that a second-order crossover is used is evident from the slight "hump" of energy in the decay. The impulse response is quite clean, with just a little ringing. The step response id shown in fig.4, and indicates that all three drive-units are connected with the same positive acoustic polarity.
Fig.3 Mission Cyrus 782, impulse response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.4 Mission Cyrus 782, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.5 shows the Cyrus 782's Cumulative Spectral Decay, or "waterfall," plot. This is the loudspeaker's frequency response calculated at discrete time intervals after the speaker is excited by a rectangular pulse. The 782's plot is excellent: the treble energy dies away very quickly and there are few ridges along the time axis that would indicate a smearing of the signal. The dark ridge near 16kHz is the computer monitor's scanning frequency and not part of the loudspeaker response, while the adjacent ridge appears to be a tweeter resonance, but is above audibility.Robert Harley
Fig.5 Mission Cyrus 782, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).