Acoustic Energy Aegis One loudspeaker Measurements

Sidebar 3: Measurements

Despite its high specified sensitivity of 90dB/W/m, I estimated the Aegis One to give 84dB(B)/2.83V/m—about what I expected, given the speaker's size and price. However, its plot of impedance magnitude and phase (fig.1) shows that the speaker is a very easy load, dropping below 7 ohms only in the lower midrange. The saddle in the magnitude trace at 50Hz indicates the tuning of the port of the speaker's rear panel, implying only moderate LF extension.

Fig.1 Acoustic Energy Aegis One, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

The distinct wrinkles in the impedance traces between 200Hz and 300Hz are associated with cabinet resonant modes. Investigating the cabinet's vibrational behavior with a simple plastic-tape accelerometer revealed two strong modes, at 270Hz and 280Hz (fig.2), which I assume contributed to the occasional lack of clarity in this region I noted in my auditioning. Some "pumping" of the cabinet walls can also be seen at the port-tuning frequency. The rear wall is very much livelier than the top and side walls; thankfully, it faces away from the listener, so its effect on the perceived clarity will be reduced.

Fig.2 Acoustic Energy Aegis One, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the cabinet sidewall. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)

Fig.3 is a composite graph showing the farfield response of the Aegis One averaged across a 30-degree horizontal window on the speaker's tweeter axis, as well as the nearfield responses of the woofer and port and their complex sum (taking into account phase and their physical separation). The port output is the well-defined bandpass curve centered on 50Hz, the frequency of the corresponding notch in the woofer's output. Although there are a couple of midrange resonances apparent in the port's response, these are well down in level and should not have any subjective consequences. Higher in frequency, though, the overall balance is quite flat for such an inexpensive speaker; the AE's on-axis behavior is characterized by a lack of energy in the mid-treble.

Fig.3 Acoustic Energy Aegis One, anechoic response on-axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the nearfield woofer and port responses and their complex sum plotted below 300Hz.

Acoustic Energy
US distributor: Audiophile Systems
8709 Castle Park Drive
Indianapolis, IN 46526
(317) 849-5880