However, as shown by the frequency-response traces (fig.4), the second-order rolloff of the sealed-box alignment results in more mid- and low bass than would be expected from the woofer tuning frequency: there is useful output down to 30Hz or so. The impedance graphs suggest that the woofers of both samples were tuned to the same frequency, 46Hz, which implies modest bass extension. The Smaller Advent's enclosure was indeed quite lively, both samples showing a series of strong resonant modes in the midrange (fig.3).įig.3 The Smaller Advent (SN 47106), cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the center of the cabinet's side panel (MLS driving voltage to speaker, 7.55V measurement bandwidth, 2kHz). The small wrinkles in the impedance traces suggest the presence of cabinet resonances of some kind. (2 ohms/vertical div.)įig.2 The Smaller Advent (SN 47106), electrical impedance (solid) and phase (dashed). Despite the specification, the impedance remains above 4 ohms at all frequencies.įig.1 The Smaller Advent (SN 47877), electrical impedance (solid) and phase (dashed). The Advent's impedance, however, was not too demanding of current, as can be seen from the impedance graphs for 47877 (fig.1) and 47106 (fig.2). Both figures are 2–3dB below the average for modern speaker designs.
They were very similar, though 47106 was slightly less sensitive than 47877 as measured on the tweeter axis: 84.5dB(B)/2.83V/m vs 85.5dB(B)/2.83V/m. 4786, the latter manufactured on October 30, 1972, according to the tweeter chassis. I performed a complete set of measurements on the two samples of the Smaller Advent, serial nos.
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