- Written by John E. Johnson, Jr.
- Published on 15 February 2012
The Design of the Bryston 10B-SUB Active Stereo Crossover Network
By "Active" this means that the Bryston has powered (wall socket AC) electronics to perform the crossover, as compared to "Passive" crossover networks that are capacitors, resistors, and inductors inside speaker enclosures.
The 10B-SUB is active, and as you can see from the photo of the inside of the chassis, shown below, there are numerous components. There have to be, because of all the choices for crossover frequencies (low-pass choice is independent of high-pass choice) and slopes.
OK, so here was my problem. I have two full-range electrostatic speakers (ESLs) as the front left and right channels, along with two subwoofers that are connected to the left and right subwoofer outputs on my processor. Unfortunately, the slope for the bass management is only first order, i.e., 6 dB/octave.
With ESLs, even with full range models, deep frequencies, i.e., 30 Hz, will cause the membrane to touch the stators, causing a popping noise. So, pipe organ music, rock music, action movies, etc., cause a problem when I listen at loud levels.
I set the bass management in my processor at 60 Hz crossover (low-pass) to the subwoofer outputs, but the slope is not steep enough, and even with signals at 20 Hz, I could still hear a significant amount of sound coming from the ESLs. I ended up setting the low-pass frequency in the processor to 120 Hz to keep low frequencies out of the ESLs. Then, I ended up with too much upper bass coming from the subwoofers.
I put up with this problem for a long time, and then, one day, I remembered that Bryston makes active crossovers. So, I contacted James Tanner, told him what my problem was, and he shipped me the 10B-SUB, which is optimized for use with subwoofers.
I received the black version, but it also comes in silver, shown below, with a close-up of the left front panel.
You can see on the front panel in the photo above that there are three sets of control knobs on the left and on the right. The first one on the left controls the low-pass frequency, and there is a slider switch nearby to select the slope (6 dB, 12 dB, or 18 dB per octave). The second knob from the left is an attenuator for adjusting the output of the high-pass section, and the third knob selects the high-pass crossover frequency, with a slope selector underneath.
The rear panel has a left and right channel XLR input and two XLR outputs for each channel, one for the low-pass signal, and one each for the high-pass signal. A slider switch sets the crossover for functioning as 2 Way Stereo (the configuration I used), 3 Way Mono (this requires two 10B-SUB crossovers to tri-amplify two speakers, each with three drivers), and Mono Low Pass (for use with one subwoofer).