Quested's SB10 subwoofer is also made with black-ash-veneered 25mm MDF, and its amplifier and crossover electronics come as a separate 1U controller, rather than being built in. This has the advantages that the controls are easy to access and the circuitry is subjected to less vibration. Substantial speaker cables connect the unit to the speaker cabinet, and combi-jack/XLR connectors are provided for the audio inputs. Line-level outputs are fed to the main active speakers via XLRs. The subwoofer can be bypassed from a button on the rack unit's front panel, allowing the main speakers to be heard in isolation without the low-cut filtering that is applied when the subwoofer is active. The control unit also provides gain, crossover-frequency, and phase adjustment, with a button for inverting the subwoofer's phase — something that the constraints of possible room positions sometimes require. A Test button activates an onboard pink-noise source for setting up, although this is filtered, as only low-frequency content is required.
Essentially, the SB10 speaker is a conventional passive, ported design using a single ten-inch long-throw driver powered by the 215W amplifier in the rack unit. It measures 617 x 333 x 290mm, which is surprisingly compact for such an effective subwoofer, and weighs a manageable 19.8kg. Subsonic and ultrasonic filters are built into the controller unit at 14Hz and 100kHz, where the crossover between the subwoofer and the main speakers is user adjustable in the range 40Hz-135Hz. With the S6s, the crossover frequency needs to be set to around 70Hz, or 60Hz for the S7s. (The larger S8 and S10 models apparently work well without a subwoofer, but you can still add a subwoofer if you need extra headroom at the low end.)