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Bowers & Wilkins ISW4 and SA250 Mk2 Bass Package

Passive in-wall subwoofer with matching external amplifier and back-box

Item # 700ISW4SA

This package lets you enjoy the satisfying punch of great bass without a traditional sub taking up space on your floor.

This package lets you enjoy the satisfying punch of great bass without a traditional sub taking up space on your floor.

Item # 700ISW4SA

In stock
$2,296.94 each

About the Bowers & Wilkins ISW4 and SA250 Mk2 Bass Package

High-performance hideaway bass from Bowers & Wilkins

In my book, high-quality bass is an important component of any great-sounding stereo or home theater system. But not all rooms call for a big, boxy subwoofer taking up a large chunk of valuable floor space. Cue the Bowers & Wilkins ISW4 — a passive in-wall sub that delivers high-quality bass while hiding completely out of sight.

High-performance hideaway bass from Bowers & Wilkins

In my book, high-quality bass is an important component of any great-sounding stereo or home theater system. But not all rooms call for a big, boxy subwoofer taking up a large chunk of valuable floor space. Cue the Bowers & Wilkins ISW4 — a passive in-wall sub that delivers high-quality bass while hiding completely out of sight.

This package includes the ISW4 in-wall subwoofer, a matching external power amp, and an in-wall back-box — all the pieces you need for unobtrusive bass. 

Bowers & Wilkins ISW4 in-wall passive subwoofer

The ISW4 lets you enjoy high-quality bass without sacrificing floor space (shown as part of a Bowers & Wilkins in-wall home theater system).

Twin built-in woofers offer tight, responsive bass

The old adage of "two is better than one" can be applied to subwoofers. I personally prefer the performance of two smaller drivers that combine to move more air than a single larger woofer on its own. The resulting bass is tight and responsive — terrific for music and movies alike.

The ISW4 employs two 8" hybrid paper/aramid fiber cones to deliver deep, accurate bass all the way down to 21 Hz. It's an excellent choice for your in-wall home theater or stereo music system in a medium- or large-sized room. 

Contain and improve performance

This package comes with a back-box that mounts inside your wall prior to the sub's installation. It creates a sealed acoustic chamber, which focuses and directs bass output into your listening area while reducing the amount of sound that bleeds into the adjacent room.

Matching amplification included

The ISW4 gets its power from the bundled Bowers & Wilkins SA250 Mk2 — an external, rack-mountable amplifier designed specifically for the company's in-wall subs. The amp connects to your home theater receiver or preamp/processor via a subwoofer cable, and to the ISW4 subwoofer via in-wall speaker wire.

A rich history of audio excellence

Founded in England in the 1960s, Bowers & Wilkins is known worldwide for their innovative hi-fi speaker designs and their premium headphones. Crutchfield is proud to offer a diverse selection of products from this legendary audio brand.

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Product highlights:

  • in-wall subwoofer with back-box and matching external amplifier
  • ideal for a discreet home theater or stereo music system
ISW4 passive subwoofer:
  • dual 8" hybrid paper/aramid fiber woofers
  • frequency response: 21-200 Hz (±3 dB)
  • impedance: 8 ohms
  • includes non-resonant back-box to focus sound into your room
  • paintable grille to match your décor
  • installs between two 16" on-center wall studs
  • includes mounting bracket and hardware
  • dimensions with back-box: 13-5/8"W x 55-7/16"H x 3-7/16"D
  • weight with back-box: 35.3 lbs.
  • warranty: 2 years
SA250 Mk2 mono subwoofer amplifier:
  • 250-watt Class D amplifier
  • rack-mountable with included hardware
  • front-panel volume, phase, crossover, bass extension, and EQ controls
  • balanced XLR input and output
  • unbalanced stereo line-level RCA inputs and outputs
  • binding post speaker outputs
  • signal-sensing auto on/off mode
  • 3.5mm 12-volt trigger inputs for power-on and movie/music mode
  • 16-15/16"W x 3-15/16"H x 12-3/4"D (rack spaces: 2U)
  • warranty: 2 years
  • Our 60-day money-back guarantee

What's in the box:

  • This Bowers&Wilkins Bass Package contains 3 individually boxed items:
  • ISW-4 In-Wall Subwoofer:
  • In-wall passive subwoofer
  • Mounting bracket
  • Grille
  • Frame gasket
  • Six M5 bolts
  • B&W logo sticker
  • Paint mask
  • Cutout template
  • Custom Installation booklet
  • SA250 Mk2 Amplifier:
  • Custom install subwoofer amplifier
  • 59" AC power cord
  • 3-Piece Neutrik Speakon plug
  • 2 Rack-mount brackets
  • 2 Handles
  • 4 Long screws
  • 6 Short screws
  • 10 Flat washers
  • 10 Lock washers
  • 4 Rubber hole plugs Custom Installation booklet
  • Safety and Warranty Instructions
  • ISW-4 Back Box:
  • In-wall subwoofer back box (for ISW-4)
  • Self-adhesive gasket
  • Lock-screw
  • Lock-washer
  • Lock-nut
  • Installation Diagram

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More details on the Bowers & Wilkins ISW4 and SA250 Mk2 Bass Package

Stacey B.

Features & specs

Features
Quantity in Package
Tweeter ---
Aimable Tweeter No
Woofer Composition Paper/Aramid fiber
Woofer Surround Rubber
Moisture-resistant No
Connector Type Spring post
Bi-Amp Inputs ---
Built-in Back-box Yes
Specs
Tweeter Size
Midrange Size
Woofer Size 8
Cutout Size ---
Power Range (Watts) ---
Sensitivity ---
Impedance (Ohms) 8
Frequency Response 21-200Hz
Parts Warranty 5 Years
Labor Warranty 5 Years

Product Research

Features
ISW-4 Subwoofer
SA250 Amplifier
ISW-4 BB

Features

Overview: This Bowers&Wilkins Bass Package features a B&W ISW-4 in-wall subwoofer, with matching ISW-4BB back box in-wall subwoofer enclosure, and an SA250 Mk2 power amplifier.

ISW-4 Subwoofer

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 designed to be 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 resists 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 installation, the back box will need to be covered with sheetrock (plasterboard) and 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 placed, 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 extend 0.25" from the wall.

Note: The mounting frame and grille are paintable.

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, 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 close 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 down side. Subwoofers positioned near corners often generate more low-frequency room resonances, making the bass more uneven with frequency.

SA250 Amplifier

Custom Install Subwoofer Amplifier: The Bowers & Wilkins SA250 Mk2 is designed to power and apply the correct equalization to the included ISW-4 custom install subwoofer, or an optional ISW-3 in-wall subwoofer (sold separately). There is a switch on the rear-panel to indicate the connection of either the ISW-4 or an ISW-3. The SA250 Mk2 amplifier is not suitable for driving any other subwoofers or loudspeakers,

250W Class D Amplifier: The B&W SA250 Mk2 employs a 250W Class D amplifier that stays cool even when listening to demanding movie and music soundtracks at high volume levels. The SA250 Mk2 can drive one or two identical subwoofers in parallel. If you need more than two subwoofers in the installation, or if you want separate left and right channel subwoofers in a stereo installation, you will need more than one SA250 Mk2 amplifier.

Balanced & Unbalanced Connections: The SA250 Mk2 subwoofer amplifier is equipped with balanced (XLR) and unbalanced (RCA) inputs and outputs. There is a mono XLR balanced input and a stereo RCA unbalanced input, as well as corresponding outputs to daisy-chaining the audio signal to another SA250 Mk2 amplifier.

  • Mono XLR Input: The mono XLR input is the preferred connection. It provides the highest-quality signal with the least amount of noise.
  • Stereo RCA Input: The stereo RCA inputs let you combine both left and right channels into one or two subwoofers using a single SA250 Mk2. If you only have a single (mono) channel input, then simply use the left RCA input only.
  • Linked Outputs: There are corresponding outputs for the balanced (XLR) and unbalanced (RCA) inputs to daisy-chain the low-frequency signal to another SA250 Mk2 amplifier.

Note: If you want to maintain stereo separation by having a subwoofer for each channel, you will need a second SA250 Mk2. In this case, you can use the balanced or unbalanced inputs.

Binding Post & Neutrik Speakon Speaker Output Terminals: The Bowers & Wilkins SA250 Mk2 is outfitted with two sets of binding post terminals and a 4-pole Neutrik Speakon connector for connection of a single in-wall subwoofer or two in-wall subwoofers. The gold-plated binding post terminals will accept bare wire (up to 12AWG), pin-connectors, spade-lugs, and banana plugs (single or dual).

Front-Panel Controls: The following subwoofer amplifier controls are found on the front-panel of the Bowers & Wilkins SA250 Mk2.

  • Volume: Adjust the Volume of the subwoofer amplifier relative to the other loudspeakers in your system. Use a wide variety of program material to get an average setting. A setting that sounds impressive on one soundtrack may sound overpowering on another.
  • Low-Pass Filter: Adjust the Low-Pass Filter to give the smoothest transition between the subwoofer and your loudspeakers. In a home theatre system, the subwoofer (LFE) signal is a separate channel rather than an extension of the signal to the other speakers. The Low-Pass Filter should be switched to Off in this case, because the AV will processor provide all the necessary filtering.
     
  • Phase: Normally the phase will be set to 0-degrees, but if your subwoofer is positioned at a distance significantly different from your other speakers, or the power amplifier driving the other speakers happens to invert the signal, the 180 position may be preferable. Listen with the switch in both positions and choose the one that gives the fullest sound.
     
  • Bass Extension: The Bass Extension switch offers three options of subwoofer bass extension. Position A gives the greatest extension and position C gives the least extension. Position B provides a compromise setting. If the system is to be used at very high volume levels or in a large listening room, restricting the bass extension by selecting either B or C may help ensure that the subwoofer is not asked to exceed its performance limits. In most situations the Bass Extension switch should be left in position A.
     
  • Equalization: The Equalization switch alters the subwoofer bass roll-off alignment appropriate to Movies or Music listening. The Movies position is more suited to the demands of action movie low frequency effects. The Music position is suited to a faster more accurate musical tracks.

3-Way Power Switch: The Bowers & Wilkins SA250 Mk2 subwoofer amplifier is best switched on after any other components and switched off first. The amplifier's 3-way power switch can be set to Standby, Auto, or On.

  • Standby: The subwoofer amplifier will become active when 12V is applied to its Standby Trigger input (3.5mm). When 0V is applied to the trigger, the subwoofer amplifier will return to the Standby state. The unit's indicator will glow green when the subwoofer amplifier is active and red when the subwoofer amplifier is in Standby.
  • Auto: When an input signal is detected, the subwoofer amplifier will automatically become active and the indicator will glow green. The subwoofer amplifier will return to Standby after about 5 minutes with no input signal. Some AV processors incorporating an automatic set up procedure may be confused by a subwoofer amplifier with an auto On/Standby function and a potentially damaging fault condition may arise. The subwoofer amplifier is best left switched on and fully active during set up if such a processor is used.
  • On: The subwoofer amplifier will remain fully active and the indicator will glow green.

12V Triggers: The Bowers & Wilkins Mk2 is equipped with a Standby Trigger Input and an Equalization Trigger Input, each consisting of a 3.5mm minijack on the rear-panel. The subwoofer amplifier will become active when 12V is applied to its Standby Trigger input and return to Standby when 0V is applied. The Equalization Input is designed to receive a 12V signal that will toggle the Movies/ Music setting at the front panel. Set appropriately, the 12V trigger output of a processor can automate ideal performance of the subwoofer.

Mounting Options: The SA250 Mk2 can simply be placed on a tabletop surface using the pre-installed feet. The subwoofer amplifier can also be installed in a standard 19" equipment rack by removing the pre-installed feet and attaching the included brackets and handles (hardware to mount the brackets to your component rack is not included). Ensure that once installed, the amplifier is well ventilated and that its ventilation apertures are not obstructed.

  • Dimensions with Pre-Installed Feet: 16.9375" (w) x 3.9375" (h) x 14.1875" (d)
  • Dimensions with Brackets/Handles: 19.0" (w) x 3.5" (h) x 15.5625" (d)

Detachable AC Power Cord: The Bowers & Wilkins Mk2 subwoofer amplifier includes a detachable 59" AC power cord. If the system is taken out of use for a long period, disconnect the subwoofer amplifier from the mains power supply.

ISW-4 BB

In-Wall Back Box: The ISW-4 BB back box in-wall enclosure is required for proper installation and optimal performance of the Bowers & Wilkins ISW-4 in-wall subwoofer. The ISW-4BB back box is constructed of heavy-duty MDF and lined with dense polyfill, plus includes integrated metal mounting brackets at the top and bottom (mounting screws and bolts are not provided).

  • The back box enclosure measures 13.875" (w) x 57.75" (h) x 3.5" (d) and installs between two 16" OC wood studs or built into a brick/block wall. In both installation, the back box will need to be covered with sheetrock (plasterboard) and 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 Phillips-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 placed, 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 subwoofer's grille mounts between the speaker baffle and frame bezel. The grille and frame bezel extend 0.25" from the wall.

Note: The mounting frame and grille of the ISW-4 in-wall subwoofer are paintable.

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