![]() ![]() ![]() The peak in the midbass is almost entirely an artifact of the nearfield measurement technique, the tuning of the woofers being apparently maximally flat. They behave identically, with a sharply defined minimum-motion notch at 27Hz and a steep, well-controlled rolloff above 250Hz or so. The green trace in fig.3 shows the response of the twin woofers. Other than a couple of very-low-level peaks around 200Hz, the rolloff above that region is smooth. It does peak between 20 and 30Hz, but there is a secondary peak an octave above the actual tuning frequency. The red trace in fig.3 shows the port's output measured in the nearfield. The saddle centered at 22Hz between the two lower-frequency impedance peaks in fig.1 suggests that this is the tuning frequency of the big, downward-firing port. A couple of very-low-level modes can be seen around 400Hz, as well as a longer-lasting but still low-level one in the midbass.įig.2 Aerial Acoustics 20T V2, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of head-unit side panel (MLS driving voltage to speaker, 7.55V measurement bandwidth, 2kHz). Fig.2, for example, is a cumulative spectral-decay plot calculated from the accelerometer's output when it was fastened to the center of the head unit's sidewall. Testing with an accelerometer revealed that both the 20T V2's head unit and bass bin are extremely inert. The impedance traces are free from the small wrinkles that would indicate the existence of cabinet panel resonances. ![]() The impedance remains above 10 ohms in the treble, which will result in a slightly tipped-up tonal balance if the speaker is driven by a tube amplifier with a typically high output impedance.įig.1 Aerial Acoustics 20T V2, electrical impedance (solid) and phase (dashed). Fortunately, the electrical phase angle at those frequencies is low, but with an impedance that stays between 4 and 6 ohms throughout most of the bass and midrange, the Aerial needs a partnering amplifier that's comfortable with driving low impedances. The electrical impedance (fig.1), however, is very similar, with minimum values of 3.25 ohms at 24Hz and 3 ohms at 228Hz. The Aerial Acoustics 20T V2 is specified as having a voltage sensitivity of 90dB/2.83V/m my estimate was somewhat lower, at 88dB(B)/2.83V/m on the tweeter axis, which is slightly lower than my measurement of the original 20T. The quasi-anechoic measurements were all performed using DRA Labs' MLSSA system and a calibrated DPA 4006 microphone. ![]()
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