Focal ISUB BMW 4 | 4-Ohm Plug & Play BMW Under-Seat Subwoofer Upgrade
Vehicle-specific 200mm under-seat subwoofer for selected BMW, MINI, Rolls-Royce and Toyota Supra factory audio systems.
Upgrade BMW Under-Seat Bass with a 4-Ohm Subwoofer
The Focal ISUB BMW 4 is a vehicle-specific 200mm under-seat subwoofer designed to improve bass depth, impact and control in selected BMW-family audio systems requiring a 4-ohm replacement.
Its Black Polyglass cone, neodymium motor and integrated vehicle spacer support a discreet upgrade within compatible original under-seat locations.
BMW Under-Seat Subwoofer Compatibility
Designed for selected BMW-family under-seat woofer locations requiring a 4-ohm replacement and a compatible original or aftermarket 4-ohm amplification system. Compatibility varies by vehicle, production year, factory audio system, amplifier configuration and speaker position. Do not substitute a different impedance version. Please refer to the Compatibility Guide or contact your nearest Authorised Focal Australia Dealer to confirm compatibility.
BMW under-seat woofers are available in different impedances. Physical fitment does not confirm that the 4-ohm ISUB BMW 4 is electrically suitable for every original amplifier.
Confirm the exact factory audio package, original woofer impedance, amplifier configuration and left or right under-seat position before purchase.
Designed for Selected Original 4-Ohm Amplification
The ISUB BMW 4 is intended for selected factory or aftermarket systems that require a 4-ohm under-seat woofer. In confirmed applications it can retain the compatible original amplification.
It should not replace a 2-ohm or 8-ohm woofer without a complete amplifier and system assessment.
200mm Black Polyglass Subwoofer Cone
The 200mm Black Polyglass cone combines a damped cellulose-based structure with additional rigidity from fine glass microbeads.
This supports controlled low-frequency movement and helps bass notes sound defined and balanced.
Neodymium Motor and Long-Excursion Performance
The compact neodymium motor provides strong magnetic control within the restricted under-seat location. A published 6.5mm Xmax supports useful cone movement for improved bass output.
Actual performance depends on the original amplifier, factory signal processing, enclosure behaviour and installation quality.
Correct ISUB BMW 4 Technical Specifications
Product type: Vehicle-specific under-seat subwoofer
Woofer: 200mm / 8-inch Black Polyglass cone
Nominal power: 90W RMS
Maximum power: 180W
Nominal impedance: 4 ohms
Sensitivity: 83dB at 2.83V/1m
Frequency response: 35Hz-200Hz
Motor: Neodymium
Surround: Butyl rubber
Voice-coil diameter: 50mm / 2 inches
Maximum linear excursion: 6.5mm Xmax
Mounting depth behind the mounting surface: 36mm
Approximate overall chassis diameter: 217mm
Approximate chassis footprint: 162mm x 162mm
Net weight: 970g
Mounting accessories: Supplied
Speaker grille: Not supplied
The 83dB figure is the published system sensitivity and should not be labelled as maximum SPL. The 217mm dimension describes the overall chassis diameter rather than a universal cut-out size.
Difference Between ISUB BMW 4 and ISUB BMW 2
The ISUB BMW 4 has a 4-ohm nominal impedance and is intended for compatible original or aftermarket 4-ohm systems.
The ISUB BMW 2 has a 2-ohm nominal impedance and is intended for compatible powered upgrades using approved 2-ohm-stable amplification. The two versions are not interchangeable.
Plug & Play Under-Seat Integration
A dedicated connector and chassis-integrated spacer support installation in selected original BMW under-seat woofer locations without cutting compatible factory speaker wiring.
Plug & Play does not remove the need to confirm impedance, mounting clearance, seat movement, wiring condition, acoustic sealing and factory amplifier compatibility.
Sold Individually for Position-Specific Replacement
The ISUB BMW 4 is supplied as an individual subwoofer. Many BMW systems use separate left and right under-seat woofers, but the required quantity must be confirmed for the vehicle.
Where a matched pair is used, replacing both sides can provide more consistent output and tonal balance.
Compatible BMW, Alpina BMW, MINI, Rolls-Royce and Toyota Supra Applications
The ISUB BMW 4 is listed for selected BMW and Alpina BMW vehicles, selected MINI and Rolls-Royce models, and selected Toyota Supra applications.
These are broad model groups. Exact compatibility depends on the original under-seat woofer impedance, factory amplifier and intended speaker location.
Factory Equalisation and Bass Processing May Remain
Replacing the under-seat woofer does not remove factory equalisation, bass limiting, active crossover settings or volume-dependent processing applied by the original audio system.
A compatible amplifier or DSP may be required where additional output or tuning control is desired.
Retain the Original Under-Seat Location
In a confirmed application, the ISUB BMW 4 remains concealed beneath the original seat area and uses the compatible factory enclosure and trim.
Professional Installation Recommended
Professional installation by an Authorised Focal Australia Dealer is recommended. The installer can confirm original impedance, amplifier compatibility, connector type, mounting clearance, seat movement, polarity and system tuning.
Confirm Compatibility Before Purchasing
Designed for selected BMW-family under-seat woofer locations requiring a 4-ohm replacement and a compatible original or aftermarket 4-ohm amplification system. Compatibility varies by vehicle, production year, factory audio system, amplifier configuration and speaker position. Do not substitute a different impedance version. Please refer to the Compatibility Guide or contact your nearest Authorised Focal Australia Dealer to confirm compatibility.
Do not order the 4-ohm version solely from the vehicle model or speaker dimensions. Confirm the factory audio package, original under-seat woofer impedance and amplifier configuration before purchase.
4-Ohm Focal Inside Bass for Compatible BMW Systems
The Focal ISUB BMW 4 combines a 200mm Black Polyglass cone, neodymium motor and vehicle-specific under-seat chassis. In a compatible 4-ohm system it provides deeper, stronger and more controlled bass while retaining the original amplifier, interior and under-seat installation location where approved.
