Skip to content

Need big sound, slamming bass, and audiophile bass extension, but don’t want to see where it comes from? Then the new ISW-4 in-wall subwoofer is the product for you. Its two long-throw 200mm (8in) drivers allow the ISW-4 to move large volumes of air needed for high-quality low-frequency output but is nicely hidden inside a wall. Powered by a separate audiophile-standard 250W Class D amplifier the SA250 Mk2, the system keeps its cool even when the music movie action is whipping up a storm.


1-year manufacturer's warranty


  • The speaker is housed in its sturdy back box for rock-solid stability and minimum sound bleed
  • Back Box mandatory for custom installation

Video Review:

In-Wall Passive Subwoofer:
The Bowers & Wilkins ISW-4 in-wall passive subwoofer features two long-throw 8" paper/aramid fiber cone woofers with rubber surrounds for high-quality, low-frequency bass output that can be hidden away in the wall. The ISW-4 is specifically powered by the included SA250 250W Class D amplifier. The ISW-4 in-wall subwoofer is perfect for both multichannel home theater and 2ch stereo applications.

Gold-Plated Spring-Post Terminals:
The B&W ISW-4 in-wall passive subwoofer is outfitted with gold-plated, spring-post terminals that will accommodate bare speaker wire (up to 12AWG), pin connectors, and banana plugs (single only). The gold-plated terminals provide excellent audio signal transfer and resist corrosion.

In-Wall Installation:
The ISW-4 in-wall passive subwoofer is primarily intended for installation into new construction of drywall (stud wall) and solid (brick or block-work) walls, but can also be installed in existing drywall construction (see "Custom Installation" booklet for further details). The included ISW-4BB back box in-wall enclosure is required for optimal performance and operation of the ISW-4 in-wall subwoofer.

The back box enclosure installs between two 16" OC wood studs or built into the brick/block wall. In both installations, the back box will need to be covered with sheetrock (plasterboard) followed by a plaster skim.
The ISW-4 will then require a rectangular cutout measuring 10" (w) x 19" (h) x 3.75" (d) for the included mounting bracket to fit into the installed back box. The mounting bracket secures into place using the integrated "dog-ear" clamps and Philips-head screws (make sure to leave 1" of clearance around the cutout to accommodate the "dog-ear" clamps.
Once the mounting bracket is secured in place, the in-wall passive subwoofer, along with the included foam gasket, can be placed inside the mounting bracket and secured using the supplied M5 bolts.
Finally, the supplied grille mounts between the speaker baffle and frame bezel. The grille and frame bezel extends 0.25" from the wall.

Subwoofer Positioning
The human ear poorly perceives the source location of low-frequency sound, so the position of subwoofers in the listening room is generally less critical compared to full-range speakers. That said, however, the best results are usually obtained if the subwoofer is placed between the left and right speakers or in the vicinity of one of them. If two subwoofers are used it is best to put one near the left and one near the right speaker.

  • Locating a subwoofer on one side wall of the listening room, even behind the listening position, is also possible but generally results in inferior imaging. It may be an acceptable compromise, however, especially in multichannel AV systems, if domestic considerations dictate.
  • As with all speakers, the proximity of room boundaries affects the sound of a subwoofer. Bass volume increases as more surfaces come into proximity with the speaker. Unlike full-range speakers, however, the overall system balance can be corrected by adjusting the volume level of the subwoofer. The more boost gained from the room, the lower the volume can be set and the less hard the subwoofer has to work; but there is a downside. Subwoofers positioned near corners often generate more low-frequency room resonances, making the bass more uneven with frequency.

Technical Specifications:

Back Box Dimensions
Height: 1406mm (55.4 in)
Width: 345mm (13.6 in)
Depth: 86mm (3.4 in)
Box Net Weight
9.6kg (21.2lb)