B&W 683 Surround Speaker System Measurements

Measurements

All measurements presented here were taken with the grilles removed. The measured responses with the grilles in place (not shown) were rougher, particularly above 4.5kHz. The nominal impedances were drawn from interpretation of the measured impedance curves (not shown).

All figures: Violet curve: pseudo-anechoic response on the tweeter axis, averaged across a 30° horizontal window, combined with nearfield responses of the woofers and port). All measurements were taken at 1 meter.

Model 683
Minimum impedance: 3.5Ω at 100Hz
Nominal impedance: 6Ω (below 6Ω from 78Hz to 900Hz)
Port tuning: 30Hz with the port open; 43Hz with the port fully blocked with the supplied foam "bungs"
Effective bass extension (-10dB): 29Hz (port open)
Sensitivity: 86dB/2.83V/m

The 683's impedance phase angle was more capacitive than is typical of most speakers at low frequencies (less so with the port bung in place). I would judge this speaker to be somewhat more difficult to drive than average, though any competent amplifier comfortable with a 4Ω load should have no difficulty with it.

Fig. 1: B&W 683, pseudo-anechoic response, off-center in the horizontal plane, at 45° (red) and 60° (blue).

While the overall response of the 683, shown in Fig. 1, was within +/- 3.8dB from 41Hz-20kHz, it was more uneven than I would have expected from the positive listening results. The off-axis results also show a significant dip at 2kHz. The vertical responses shown in Fig. 2 strongly suggest that you avoid listening positions significantly below tweeter height.

Fig. 2: B&W 683, pseudo-anechoic response at 15° above (red) and 15° below (blue) the tweeter axis.

Model HTM61
Minimum impedance: 3.2Ω at 145Hz
Nominal impedance: 6Ω (below 6Ω from 90Hz to 900Hz)
Port tuning: 49Hz (port open)
Effective bass extension (-10dB): 45Hz (port open)
Sensitivity: 87dB/2.83V/m

The impedance results suggest that the HTM61 is of average difficulty to drive, as long as your amplifier can drive loads that drop below 6Ω over a significant portion of the audible frequency range.

Fig. 3a: B&W HTM61, pseudo-anechoic response, off-center in the horizontal plane, at 45° (red) and 60° (blue) on the woofer side.

Fig. 3b: B&W HTM61, pseudo-anechoic response, off-center in the horizontal plane, at 45° (red) and 60° (blue) on the midrange side.

The averaged response of the HTM61 (violet curve, Figs. 3a and 3b) shows a significant dip from about 2kHz to 7kHz, making the speaker a poor spectral match for the left and right 683s. While bench-test results don't always correlate with listening tests, they do here. The lack of presence and voice intelligibility I heard could almost be predicted by the frequency response. However, the HTM61 is more uniform from 66Hz to 1.6kHz (+/-1.3dB) than the 683, even though the two speakers use the same midrange driver.

The off-axis responses of the HTM61 varied depending on whether the measurements were taken on the woofer side or the midrange side. But once you're well off-axis, the speaker develops the uneven response typical of horizontally configured drivers, though it's slightly better in the direction of the midrange (Fig. 3b) than on the woofer side (Fig. 3a).

Fig. 4: B&W HTM61, pseudo-anechoic response at 15° above (red) and 15° below (blue) the tweeter axis.

The vertical response (Fig. 4) indicates that the ear height relative to the tweeter (within the measured +/- 15 ° window) is non-critical when the speaker is positioned horizontally.

Model 685
Minimum impedance: 5.7Ω at 195Hz
Nominal impedance: 8Ω
Port tuning: 47Hz (port open)
Effective bass extension (-10dB): 36Hz (port open)
Sensitivity: 87dB/2.83V/m

Since I used the B&W 685 as a center-channel for much of the review, we also ran a full set of measurements on that speaker as well. With its non-critical nominal and minimum impedances, the 685 should be an easy load to drive.

Fig. 5: B&W 685, pseudo-anechoic response, off-center in the horizontal plane, at 45° (red) and 60° (blue).

The speaker's front horizontal response, taken on the tweeter axis and averaged in the same manner as described above, is shown in Fig. 5 (violet curve). Despite the 685's somewhat uneven response, the reasons I preferred it to the HTM61 are clear from Fig. 5. It is a far closer spectral match to the 683—surprisingly so, considering the fact that the only driver common to both speakers is the tweeter. This results in a far more uniform overall balance across the front three channels.

Fig.6: B&W 685, pseudo-anechoic response at 15° above (red) and 15° below (blue) the tweeter axis.

Fig. 6 shows the vertical response of the 685, which suggests that you'll want to avoid sitting significantly higher or lower than the tweeter. If you must, then tilt the speaker accordingly, or even try positioning it upside down.

Despite the slightly uneven quality of these measurements, my very positive feelings about the sound of this system, the HTM61 excepted, has not changed. I set it up again following my review of the far more-expensive PSB Synchrony One system, and I continue to be impressed by the remarkable value the B&Ws offer. The lack of a dedicated center-channel that is up to the performance level of the 683s is a bit of a bummer, but the 685 is a worthy substitute, if you can accommodate using it vertically. The other center channel in the 600 series, the HTM62, was not reviewed—Thomas J. Norton.

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