Infinity Beta Series Surround Speaker System Measurements
All measurements on the Beta 50 and Beta C360 center were made with the grilles installed. As expected, the responses of both speakers with their grilles in place was less smooth at mid and high frequencies, with the degradation more pronounced on the B50 than on the C360.
The impedance of the Beta 50 is typical of a ported enclosure tuned to approximately 37Hz, with minimum impedance of 5Ω at 118Hz. I would rate the speaker's nominal impedance at a conservative 6Ω. With this impedance and a sensitivity of approximately 89dB/2.83V/m, the Beta 50 should be an easy load for any well-designed amplifier or AV receiver.
Fig.1: Infinity Beta 50, pseudo-anechoic response off horizontal axis at 45° (red) and 60° (blue).
The horizontal front response of the Beta 50 is shown in Fig.1 (violet). This is the pseudo-anechoic response averaged over a 30° forward horizontal angle, taken at tweeter height, combined with the nearfield responses of the woofers and port.
The overall ±15° averaged front horizontal response of the Beta 50 is relatively smooth, though a significant dip at 650Hz, together with another smaller dip in the low treble, may account for the slightly limited dynamics MF observed. The top end, in particular, looks very smooth. The horizontal off-axis response tracks the on-axis result fairly closely, apart from the expected rolloff at higher frequencies. With room gain, the bass should hold up strongly to below 40Hz (-10dB at 37Hz, close-miked, pseudo-anechoic response).
Fig.2: Infinity Beta 50, pseudo-anechoic response at 15° above (red) and 15° below (blue) tweeter.
Fig.2 shows the same averaged horizontal front response (purple), this time overlaid with the vertical responses taken at +15° (red) and –15° (blue). These curves suggest that a seated ear height slightly below the tweeter may produce the smoothest response.
The Infinity Beta C360's sealed cabinet is tuned to about 46Hz. Its minimum impedance measured 5.3Ω at 123Hz. I would rate its nominal impedance at a conservative 6Ω. The Beta C360's sensitivity measured approximately 90dB/2.83V/m, and like the Beta 50, it should be an easy load.
Fig.3: Infinity Beta C360, pseudo-anechoic response off horizontal axis at 45° (red) and 60° (blue).
The measured front horizontal response of the Beta C360, taken on the tweeter axis and averaged in the same manner as described above for the Beta 50, is shown in Fig.3 (violet curve). The effective bass extension is approximately 46Hz (-10dB). Apart from some mild prominence in the region from 500Hz to 2kHz—which may add a bit of emphasis to voices—the response is actually smoother through the midrange than the B50, since it does not have the tower's 650Hz suckout. The highs are slightly less smooth than the B50's, but not by much. The reduced output below about 300Hz may be intentional, to compensate for the reinforcement often generated in this range when a speaker is placed on top of a large object, like a big-screen TV.
The off-axis response of this 3-way speaker is a little disappointing for a 3-way design, though not out of line for a speaker in this price range. The result was quite uneven at the extreme angles (45° and 60°) we typically use for this measurement. But up to 30° off-axis (not shown), the response follows the on-axis reaponse quite closely, apart from a narrow +4dB peak centered at about 1.2kHz.
Fig.4: Infinity Beta C360, pseudo-anechoic response at 15° above (red) and 15° below (blue) tweeter.
Fig.4 shows the vertical response of the Beta 360 at + 15° (red) and –15° (blue), overlaid again with the averaged front horizontal response. The +15° result shows a severe dip in the 2-4kHz region; the –15° result is far smoother—appropriate for a speaker that will likely be located atop a television and above ear level.—Thomas J. Norton
All figures: Violet curve: pseudo-anechoic response on tweeter axis, averaged across a 30° horizontal window, combined with nearfield woofer (and, in the Beta 50, port) response. All measurements taken at 1 meter.