Focal ISUB BMW Inside Series Direct Fit Sub Under Seat Subwoofer 4ohm
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The Focal ISUB BMW 4 is a single 8-inch, 4-ohm direct-fit under-seat subwoofer for BMW and MINI, rated at 90W RMS, from Focal's Inside Series.
This listing is the single 4-ohm unit. The ISUB BMW Inside Series is also available as a pair of ISUB BMW 4 subwoofers, the ISUB BMW 2 (2 ohm), and the ISUB BMW 8 (8 ohm).
Key specifications
- Type: 8-inch under-seat subwoofer, single
- Impedance: 4 ohms
- Power handling: 90W RMS (180W peak)
- Sensitivity: 83dB
- Frequency response: 35Hz–200Hz
- Cone: Polyglass with butyl rubber surround
- Magnet: neodymium
- Grille: not included
Subwoofer
The ISUB BMW 4 is designed specifically for BMW and MINI, fitting directly into the original under-seat location via an integrated chassis spacer — no cutting or vehicle modification required. Its neodymium motor and Polyglass cone deliver clean, powerful bass, and at 4 ohms it works with your existing amplification straight away. If you want a complementary speaker upgrade, the Focal IC BMW 100L Inside Series coaxial speakers are also designed for direct-fit BMW and MINI installation.
Focal Inside for BMW & MINI
Focal's Inside Series audio kits are engineered to slot into factory locations, giving a significant upgrade over the original equipment without any permanent changes to your vehicle.
- Quick installation
- No wires to cut, no modifications
- 100% compatible with your vehicle
- Superior sound quality over the original unit
- Mounting accessories included
Explore the full range in Focal Inside.
Specification
| power handling | 90 watts RMS (180 watts peak) |
|---|---|
| frequency response | 35-200 Hz |
| sensitivity | 83 dB |
More specs
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What's Included
- 1 Subwoofer
- 1 Foam gasket
- Four 1" Screws
- User manual
- Focal window sticker
- Adhesive backed Focal Inside badge
Focal
About the Focal ISUB BMW 4
From our tech experts at CEN
The Focal ISUB BMW 4 is a single 8-inch, 4-ohm under-seat subwoofer from Focal's Inside Series, rated at 90W RMS (180W peak). It is designed specifically for BMW and MINI, fitting directly into the original under-seat location via an integrated chassis spacer — no cutting or vehicle modification required. The Polyglass cone, butyl rubber surround and neodymium magnet deliver a frequency response of 35Hz to 200Hz.
Who it suits
BMW and MINI owners wanting a straightforward bass upgrade without modifying their vehicle will find this a practical choice. The reversible, direct-fit design suits those who prefer a clean, factory-look installation. For a compact passive underseat alternative, see the Focal ISUB Twin Sub.
Our tech experts advise
Check your specific BMW or MINI model for compatibility before ordering — contact our team to confirm fitment. At 4 ohms, this sub works with most aftermarket amplifiers. Note that no grille is included with this unit. Car audio installation is priced per vehicle; see our Nottingham installation page for details.
Explore the full Focal range at CEN, with fast UK dispatch and expert advice from our Nottingham team. Shop all Focal
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Have it Fitted By Our Team
Our team fits car audio, stereos, dash cams and vehicle security at our workshop in Beeston, Nottingham. Tell us your vehicle and we'll confirm the parts and a fitted price.
- 1
Tell us your vehicle
Make, model and year, and what you'd like fitted.
- 2
We confirm the parts
Fascia, wiring and interfaces checked for your car, with a fitted price.
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Fitted at our workshop
Bring it to our Beeston workshop and we do the rest.
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Plug & Play Kits
Configure the solution best suited to your needs in just a few clicks.
Focal Inside Series
The Focal Inside offer is aimed at all drivers wishing to replace their car's original system with a hi-fi quality Plug & Play solution that integrates easily, without modifying the interior. Different configurations are available by brand (over 50 brands), by car model (1000 vehicle models).
Focal Car Audio
Deliver exceptional sound clarity and precision for your vehicle.
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Frequently Asked Questions
Q: What does RMS power mean?
A: RMS is the continuous power a subwoofer can handle, and it is the number that matters when matching an amplifier. Peak or max figures describe short bursts only. Match your amplifier output to the RMS rating in the Specification tab.
Q: Can CEN build or supply an enclosure and fit everything?
A: Yes. CEN supplies enclosures and offers professional installation from our Nottingham premises, including amplifier wiring. Contact us to discuss your build.
Q: Is the ISUB BMW 4 a single subwoofer or a pair?
A: This listing is a single 8 inch subwoofer. CEN also lists the ISUB BMW 4 as a pair for replacing both under-seat subwoofers.
Q: Does the ISUB BMW 4 need a separate enclosure?
A: No. It fits directly into the original under-seat location using an integrated chassis spacer, and at 4 ohms it works with the existing amplification.
Q: What's in the box with the ISUB BMW 4?
A: One subwoofer, one foam gasket, four 1 inch screws, a user manual, a Focal window sticker and an adhesive-backed Focal Inside badge.
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