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Reviewer: John Potis
Analog Sources: Merrill-Scillia Research MS2 table, Hadcock GH Export arm, Ortofon Kontrapunkt H cartridge; 1985 AR Turntable with Merrill mods/Hadcock GH Export Arm Garrott Bros Optim FGS Cartridge
Digital Source: Accustic Arts Drive 1/Audio Aero Prima SE DAC; Bel Canto CD2 & DAC3 [in for review]
Preamp: Bel Canto Pre2P, McCormack MAP-1
Power Amp: Art Audio Carissa, Bel Canto e.One REF1000 Monos, Canary CA 330 Monos, Cyber 211 Monos, Musical Fidelity A5 Integrated
Speakers: Tidal Audio Pianos, Thiel CS 2.4, Ohm Acoustics Walsh 4 with 4.5 mk.2 upgrade, Hørning Perikles, Klipsch LaScala IIs, Acoustic Zen Adagio Jr.
Speaker Cables, Interconnects and Digital cables: JPS Labs Superconductor 3
Power Cords: JPS Power AC, Analog AC, Digital AC, Aluminata and Kaptovator
Powerline conditioning: Balanced Power Technology 3.5 Signature Plus with ZCable Cyclone Power Cord
Sundry accessories: Sound Mechanics Performance Platform, 2-inch Butcher Block platforms with Quest for Sound Isol-pads, Vibrapod Isolators and Cones, Ultra & Heavy ZSleeves, Viablue QTC spikes under speakers, Auric Illuminator, Gingko Audio Mini-Clouds
Room size: 12' by 16' with 9' ceiling
Review component retail:

The 10B-Sub is Bryston's active crossover designed for satellite/subwoofer installations using 6/12/18dB Butterworth filters. Bryston makes two other versions: the 10B-STD which includes processing required for control in the mid and treble areas (70 - 4500Hz), and the 10B-LR which is extremely flexible with its programmable plug-in resistor boards. The LR version is factory set at 24dBs per octave using Linkwitz-Riley filter slopes. You simply add a plug-in resistor module to set the turn-over frequency.

When used in stereo mode, the 10B-Sub provides two mono 2-way crossovers with completely independent controls for each channel - independent as in, no interaction whatsoever between channels so there is no summing of the bass signal. Should you run stereo subs, you can low-pass each one differently to suit room conditions. You can also vary the high-pass frequencies for the main speakers - in other words, immense versatility as your chosen crossover points can be staggered as needed. All four filters have separate output connectors on the rear panel. The 10B-Sub can be ordered with XLR or RCA sockets. My review sample came with single-ended RCAs as per my request.

On the front panel, the controls are laid out in a true dual-mono fashion, left channel controls on the left, right channel controls on the right side. I like the decision not to mirror image these controls, which would be confusing. Starting at the front left corner is the stepped rotary control to select the low-pass filter. Corner frequencies include 40, 50, 60,70, 80, 90, 100, 200, 300, 400 and 500Hz. Below sits a toggle to mute the subwoofer signal. I recommend you use it prior to making changes to prevent a transient thump. Then there's a three-way switch to select between 6, 12 or 18dB filter slopes. Toward the center of the face plate is the rotary control to adjust signal strength of the high-passed feed to the main amplifier. Output adjustment is available in ten 1dB steps for a +/- 5dB range of adjustment (a 10dB range in 2dB steps version is available on special order). This is used for fine balance adjustments between main speakers and subwoofer. However, Bryston suggests that whenever possible, to make all adjustments at your subwoofer and set their gain control to '0'. This removes all of the 10B's gain stages from the signal path. Finally, we get to the rotary control for the high- pass frequencies, which match the low-pass frequencies: from 40 to 100Hz in 10Hz increments, then from 100 to 500Hz in 100Hz steps. There's another toggle for muting the high-pass band (highly recommended before making changes with the amplifiers powered up) as well as another three-position slider to select from 6, 12 and 18dBs slopes. In the center of the 10B-Sub is the display that indicates the chosen mode of operation: 2-way stereo, mono low-pass and 3-way mono. On the right side of the 10B are the exact same controls as on the left side, in the exact same orientation.

Two-way stereo mode is the mode I used. It allows for a single crossover between each of two speakers and two subwoofers for true stereo separation in the bass frequencies. Or you can connect both outputs to the inputs of a single subwoofer. L+ R Low Pass mono mode is used to sum the bass sent to a single subwoofer or pairs. Lastly, 3-way-mono mode will be used when the 10B separates the drivers in a three-way speaker. Now the 10B becomes a mono unit and two 10Bs must be used for a stereo speaker pair. On the rear panel is an IEC power inlet, a grounding post and six RCAs; one each for the right and left input signal and four outputs: stereo low-pass and stereo high-pass. In the center and just below the IEC is a three-way switch used to select from among the three aforementioned operational modes: 2-way stereo, mono low-pass and 3-way mono.

One thing not immediately obvious is that while the 10B gives you the ability to dial in filter slopes (the degree at which the signal is attenuated below the filter frequency as expressed in decibels of attenuation per octave), it also alters signal phase at that frequency. This isn't so much a feature as it is a natural byproduct of altered slopes. The 6dB position shifts the signal at the filter frequency by 90º, the 12dB by 180º and the 18dB by 270º. This should be considered when selecting the phase setting at the sub. As I found out, it can be extremely useful in blending the sub/s with the speakers. Don't forget that the same changes happen at the high-pass frequencies for the main speakers too. But it must also be understood that the phase changes are effective only at the crossover points, not over the entire speaker bandwidth. A 180º shift will not necessitate the reversing of the speaker leads. These small phase changes can result in a much-improved blend between sub and speakers and a little experimentation is strongly advised.

The Bryston 10B-Sub active crossover inserts between preamp and power amplifier/s. Those using an integrated amplifier can use the 10B-Sub as long as they can separate the integrated amp's preamp section from the power amp section, usually by removing U-shaped jumpers. If the terminology confuses you, remember that low-pass filtering does just what it implies - it passes the low frequencies and blocks out the highs. High-pass filtering does the reverse. So the right and left preamplifier outputs connect to the 10B-Sub's inputs. Then the latter's high-passed outputs connect to the power amplifier/s and the low-pass outputs to the subwoofer/s. Simple!

I would suggest the same initial settings that I used: set all the filters to 80Hz. Play some bass-heavy material and use the volume control on the subwoofer to make the volume adjustments. Match phase using the subwoofer's phase adjustments too. With the music playing, the correct phase adjustment will be the one that gives you the greatest output on and around the crossover frequency. If that sounds difficult to ascertain, it's not. You'll know the correct setting when you hear it. From then on, it's all about fine adjustments. As I moved among various speaker makes, I found in my case that different crossover slopes were required to blend subs and speakers. Again, it wasn't difficult to hear which setting was best. Once you find the right setting, everything else sounds a little wrong; the bass will sound lumpy and uneven. When you hear the most coherent transient performance around the crossover frequency, you're home, baby.