![]() ![]() The SCM 11 is somewhat unusual in having for its woofer a sealed-box alignment. It's possible that these modes are high enough in frequency to have no subjective consequencesJM certainly didn't remark on any midrange congestion that might have been laid at the door of this behavior.įig.2 ATC SCM 11, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel (MLS driving voltage to speaker, 7.55V measurement bandwidth, 2kHz). There is a slight discontinuity between 500 and 600Hz in the impedance-magnitude trace, and an investigation of the enclosure panels' vibrational behavior with an accelerometer did uncover two fairly strong resonant modes on the sidewall in this region (fig.2). Though there is a rather demanding combination of 5.5 ohms magnitude and ≤2° electrical phase angle at 3.3kHz, this shouldn't overtax well-designed amplifiers.įig.1 ATC SCM 11, electrical impedance (solid) and phase (dashed). ![]() This was probably owing to the fact that the SCM 11's impedance remains above 8 ohms for most of the audioband, with a dip to 6 ohms between 100 and 300Hz, and to 4.8 ohms in the mid-treble (fig.1). I estimated the ATC's sensitivity as being a low 82dB(B)/2.83V/mthis speaker should work best with higher-power amplifiers, though I note that JM had no drive difficulties with the Arcam Mini or Carat I57 receivers he used, and was impressed by the speaker's dynamic capabilities when he drove it with the Peachtree Nova. The SCM 11's voltage sensitivity is specified as a fairly low 85.0dB/2.83V/m this seemed a touch optimistic, as the ATC didn't seem to play any louder than the sample of the BBC LS3/5a that I routinely include when I'm set up to measure a bunch of loudspeakers. ![]()
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