*All measurements taken using DRA Lab’s MLSSA system with RCAI, calibrated ACO Pacific 7012 ½” free field measurement microphone with associated pre-amp and power supply and an automated Outline turntable.
Full-range quasi-anechoic on-axis frequency response
Microphone distance is 1 meter with calibrated sensitivity
Horizontal and vertical off-axis graphs plus listening window
Listening window is the averaged response of 5 separate measurements, on-axis, +/- 15 degrees horizontal and +/- 15 degrees vertical. In the case of floor-standing loudspeakers, we prefer to use +/- 10 degrees vertical as this more closely represents a real-world listening environment. Note: due to the measurement technique, the response below 250Hz is invalid, as represented by the above and below horizontal green bars.
5 degree increments from 0 degs to a full 90 degs off-axis. Note how the critical midrange response remains linear and consistent with uniformly decreasing spl as frequency increases. Also note the lack of tweeter bloom as far off-axis as 45 degrees. This represents an exceptional off-axis response.
Impedance and electrical phase
Note the extremely clean impedance response (free from wrinkles which would represent various forms of resonances) and linear phase with minimal phase angles. The mild phase angles ensure that this speaker is an easy load for even basic receivers.
Energy Time Curve
This measurement is a good indication of overall transient accuracy and stored energy. The graph displays the decay time of a full range impulse. The impulse occurs at 3ms and decreases uniformly to the noise floor (-45db) by 4ms. This represents a decay time of 1ms, which is superb. Large diameter woofer cones, woofers and tweeters with poorly designed motor systems and/or heavy mass and poorly constructed cabinets will often contribute to far greater decay times which damage transient accuracy, coherency and overall resolution.
Cumulative Spectral Decay
This measurement is similar to the energy time curve but displays a 3 dimensional view such that we can examine the decay time with reference to frequency. It is an exceptional tool to reveal transient accuracy and indicate various problem areas with respect to resonance and stored energy. The CSD of the Sierra Tower is exceptionally clean with good uniformity.