Figure 16. Estimated displacement (𝜇m) of audio-related structures (top graph) and automotive structures (bottom graph). Mean of five measurements corrected for zero vibration reference (displacement zero reference = 1 𝜂m, acceleration zero reference = 394.8 𝜇m/s²).
Note: Research has shown that a 3/4" MDF plate 40 x 18 inches, when excited by a loudspeaker transducer, results in a vibration displacement of 229 𝜇m. Increasing the same plate to 2-1/4" results in a vibration displacement of 18 𝜇m. The subwoofer enclosure in the Magic Bus is 3" thick Baltic Birch. The front monitor baffle is a multi-layer combination of 1" MDF, 0.375" fiberglass, 0.125" steel, and 0.125" EAR damping material (constrained layer between MDF and steel).
Reference: David Waratuke, Loudspeaker Cabinet Bracing: A Detailed Look on Do's and Dont's, Audioholics™, Jan 02, 2012.
https://www.audioholics.com/loudspeaker-design/detailed-look-proper-loudspeaker-cabinet-bracing
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Figure 10. Impedance and phase data for Dynaudio Esotar 1200 subwoofers in sealed enclosures.
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Figure 8. Reverberation spectra generated by Bruel&Kjaer 2270 Handheld Sound Meter. Impulses were generated by balloon bursts and decay data was acquired at a rate of 200 samples per second for four seconds.
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Figure 9. Impedance and phase data for Dynaudio MW180 woofers in sealed door enclosures.
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Figure 7. PAPR (https://en.wikipedia.org/wiki/Crest_factor) versus SPL. At 97 dB, the Magic Bus is capable of incredible dynamic response with substantial margin of safety over the dynamics typical of music.
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Figure 11. Impedance and phase data for Dynaudio MW150 Neo midranges in sealed enclosures.
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Figure 2. Phase plot of four-way system. Crossover topology used to achieve this is proprietary.
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Figure 5. Total Harmonic Distortion.
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Figure 15. Magnitude of acceleration (dB) of audio-related structures (top graph) and automotive structures (bottom graph). Mean of five measurements corrected for zero vibration reference (accelerometer on concrete floor).
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Figure 1. Frequency response of left (blue) and right (red) channels including mono subwoofer.
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Figure 3. Step response of four-way system.
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Figure 17. Mean threshold of human perception is about 3 𝜇m at 10 Hz diminishing to about 0.3 𝜇m at 100 Hz (compliments of Brüel&Kjær, click on graph to read entire publication).
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Figure 6. RMS Power (-3 dB Pink Noise) and SPL (unweighted, 1 sec averaging) versus volume setting. At about 97 dB, the power consumption is about 250 Wrms, scarcely above Class A operation. The Magic Bus is capable (at a volume setting of 46) of 4307 Wrms into 4.22 Ω, thus the peak power output is 8614 W !!
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Figure 4. FFT Waterfall plot of four-way system. The vertical axis ranges from 0 to -80 dB.
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Figure 13. Raw accelerometer data for audio structures. Each trace is the mean of five measurements. Brown represents accelerometer resting on concrete floor (zero vibration baseline). Violet is subwoofer, green is left door panel, and red is left front monitor. Notice that subwoofer vibration above 100 Hz overlays the baseline!
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Figure 12. Impedance and phase data for Esotar tweeters.
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Figure 14. Raw accelerometer data for automobile structures. Each trace is the mean of five measurements. Brown represents accelerometer resting on concrete floor (zero vibration baseline). Black is the seat base, blue is side window glass, and orange is the windshield. Notice that the subwoofer vibration level (from Figure 13) is better than the seat base! Clearly, enclosure isolation works!
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