RBH Signature Series surround speaker system Measurements
The RBH 1266-SE's sensitivity measured approximately 88dB/W/m, and its ported cabinet is tuned to approximately 27Hz. Its minimum impedance is 3.4ohms at 300Hz; I rate the nominal impedance at 6ohms. Overall, the speaker should be of average difficulty to drive.
The 1266-SE's pseudo-anechoic response at tweeter height, averaged over a 30° forward horizontal angle and combined with the nearfield responses of the woofer and port, is shown in Fig.1 (violet). The useful bass extends down to about 30Hz (-10dB relative to the output at 55Hz). The on-axis response is very smooth, but does show a rising trend toward the midrange and treble—or, looked at another way, there's a slight leanness through the mid- to upper bass and lower midrange. This is consistent with the listening results: not as warm-sounding as some speakers and perhaps a "little brash," leaning toward "the fast and slightly spotlit"—but (to paraphrase MF) clear and detailed without unnatural etch, edginess, or harshness. The wide off-axis response tracks the on-axis average very well, differing mainly in the typical off-axis high-frequency rolloff.
Fig.2 again shows the 1266-SE's averaged horizontal front response (violet), plus the vertical responses taken at +15° (red) and -15° (blue) relative to the tweeter. The response is, if anything, a bit flatter at modest angles above and below the tweeter than directly on-axis.
The cabinet of the 661-SE center-channel speaker is tuned to about 52Hz. I rate its nominal impedance at 6ohms; the minimum impedance was 4.1ohms at 172Hz. The speaker's sensitivity measured approximately 90dB/W/m. It appears to be of average difficulty to drive.
The 661-SE's averaged front horizontal response when used in the typical horizontal center-channel configuration, and taken in the same manner as described above for the 1266-SE, is shown in Fig.3 (violet). Here the port was closed, as MF used it in the listening tests; opening the port added a +4dB peak at about 85Hz. The useful bass extension is approximately 45Hz (-10dB relative to the output at 80Hz). The on-axis response is a little less smooth than the 1266-SE's. The wide off-axis response shows the same deep suckout we see in every woofer-tweeter-woofer center-channel speaker we've ever measured (the dip here appears to come from combing effects between the two woofers). But up to about 15° off-axis (not shown)—about the width of a typical three-seat couch 10 feet or so from the speakers—the response tracks the on-axis curve very closely, except for a narrow dip centered at around 3.5kHz and reaching a maximum of -5dB. The latter clearly comes from off-axis interference between the woofers and the tweeter.
The 661-SE's ±15° vertical off-axis performance (Fig.4) is good, with the above- and below-tweeter responses nearly identical. —Thomas J. Norton