Meridian Digital Theatre surround-sound music system Measurements DSP5000 part 2

In the time domain, the use of DSP-implemented crossover filters results in an excellent, time-coherent step response (fig.15). Note in this graph that, even though the microphone was my standard 50" away, the step doesn't start until the 8.5ms mark---equivalent to an extra time of flight of 4.5ms. This 4.5ms delay is due to the digital filters both in the A/D converter I used and in the DSP5000, but it will be subjectively inconsequential.

Fig.15 Meridian DSP5000, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Other than the tweeter resonance, the Meridian's waterfall plot on the tweeter axis (fig.16) is very clean, as is a similar plot calculated from the output of a simple accelerometer fastened to the center of the cabinet sidewall (fig.17). A resonant mode is apparent at 383Hz, but this is both low enough in level and high enough in frequency to have little subjective effect on the sound. However, the sidewall does appear to flex a little at the reflex port's tuning region of 40Hz, which might make the bass sound very slightly soft.---John Atkinson

Fig.16 Meridian DSP5000, cumulative spectral-decay plot at 50" (0.15ms risetime

Fig.17 Meridian DSP5000, cumulative spectral-decay plot of accelerometer output fastened to center of side wall. (MLS level, -3dBFS; volume control = "70"; measurement bandwidth, 2kHz.)

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