From the Measurement Lab: What Mean Measurements for Subwoofers

Are more important than frequency responses with woofers the level and distortion; Finally they become as invisible and want to create level still tidy up in deepest sound equipment.

The metrological evaluation of subwoofers seems easy, where you need to play only the lowest range of the audible spectrum. But far from it: At the rate it begins to be complicated. Each active woofer – only those eligible for Hi-Fi and surround in question – must submit the existing speaker set in the truest sense of the word.

So that this is done without complications, mainly two controllers are responsible: level and crossover frequency. But every twist of the frequency adjuster change the woofer in character from the ground up – by additional filters or equalizers for room adaptation just to mention (see picture gallery figs. 1 + 2). For the measurement, this means that you must set to defined basic settings. So far has been measured at maximum and minimum position of the frequency controller. But in practice they operate somewhere between the extremes, which also often very far apart (fig. 1) and from woofer to woofer that differ widely important comparability difficult.

And: vcf, which are often anything but linear, the average level, for example a speaker with an average 80 dB sound pressure is how much to customize? Therefore, our laboratory has created a new test program. It allows to determine the average level of the loudest octave with each frequency response measurement and adjust the woofer to measure consistently to 80 Hertz (-3 dB). In this position, frequency response (red curve in Fig. 1 + 2), cutoff frequencies and distortion behavior are determined now, complemented by frequency response at maximum (green) and minimal cross-over slider position (blue).

Are more important than frequency responses with woofers the level and distortion; Finally they become as invisible and want to create level still tidy up in deepest sound equipment. The physics can not outsmart themselves but – somewhere compromises are announced, which applies to crystallize it. Each additional octave the bass cellar means a fourfold increase in the membrane deflection at the same sound pressure. There, it is easy to imagine that, at high levels, the limits are quickly reached.

For this to happen without striking the membrane or noisy flow noise, developers limiter and filter insert (Nubert, fig. 3-5) or lower sent the level from (Logan, fig. 6). In the diagrams of “Level – & Clank history” with measurements of 85 (black) to 100 dB SPL (red) this connection is clear: the lower colored curve rises steeply and she might reach the upper level curve (fig. 5), can be expected with audible impairments.

 

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