The In Phase USW300 is a compact underseat subwoofer built to deliver powerful, deep bass in a slim, space-saving design. Its key strength is performance: this active woofer punches well above its size, with a genuinely responsive bass output that transforms the sound of a factory car audio system once added.
The subwoofer features a 5" x 8" aluminium-coned speaker — a lightweight yet stiff cone material that's robust and rarely fails — with damping material built into the cone and spider for rattle-free bass. It's housed in a die-cast aluminium chassis rather than plastic, giving it a solid, rigid structure that doesn't flex under full power, which also helps sustain consistent bass output.
Built with an integrated amplifier, the USW300 delivers 130W RMS true wattage — higher than most underseat subs on the market — with a max output of 300W. It includes a high-level speaker input, allowing it to tap directly into existing OEM vehicle wiring, and a wired remote control for on-the-fly volume and bass boost adjustment.
Measuring a compact 280mm (L) x 200mm (W) x 75mm (H), the USW300 is designed to fit discreetly under most front or rear car seats, in the boot, behind seats, or in footwells — making it a straightforward upgrade for anyone wanting more bass without the bulk of a traditional subwoofer box.
Key features:
- 300W max output, 130W RMS
- Aluminium-coned speaker with damping for rattle-free bass
- Die-cast aluminium chassis
- High-level speaker input (OEM wiring compatible)
- Wired remote for volume and bass boost control
- Compact size: 280 x 200 x 75mm
- Speaker frequency range: 40–150Hz
Note: if using with an aftermarket stereo, RCA cables are needed separately, as noted by several UK retailers of this product.
We accept all major credit and debit cards, including AMEX and other secure checkout options.
All payments are processed safely through our platform.
If you have any payment-related questions, please contact us before placing your order.
Handling time: Orders are dispatched within 1 working day.
Delivery Options:
- Standard delivery (1–2 working days): £6.25
- Next Day Delivery (Guaranteed by 1 pm): £10.45
- All orders are sent via tracked 24-hour services within the UK only
Please note:
- We do not ship to the Channel Islands or internationally.
- We’re unable to change delivery addresses once an order is placed.
- Collections are not available.
Per In Phase Audio's own site, this product is covered by a 14-Day Money Back Guarantee. Unused and unopened products can be returned within 14 days of delivery for a full refund. To initiate a return, the product must be in its original, unused condition — contact In Phase Audio's customer service team to begin the process.
All items include a 12-month seller warranty (unless otherwise stated).
Faulty Items
- Within 30 days of delivery: You may return the item for a repair, replacement, or refund
- After 30 days:
- We will first attempt a repair
- If repair is not possible, we will offer a replacement of equal value
- If neither is possible, a refund may be issued at our discretion
What the Warranty Covers
- Manufacturing faults only
- Hardware defects not caused by user damage
What is NOT Covered
The warranty does NOT cover:
- Accidental damage (drops, impact, etc.)
- Water or liquid damage
- Misuse, neglect, or improper use
- Normal wear and tear
- Software-related issues
- Any unauthorised repairs, modifications, or tampering
Any of the above will void the warranty
Refurbished / Used Devices – Important Information
All refurbished and used devices:
- Undergo a comprehensive multi-point inspection and testing process
- Are fully functional at the point of sale
Performance Expectation Notice
Older models will not perform the same as newer devices.
It is normal for refurbished/used phones to:
- Require charging once or multiple times daily, depending on usage
- Have lower performance compared to newer-generation devices
Battery and performance comparisons with brand-new or latest devices are not valid.
Battery Warranty & Battery Health
Battery Warranty
Batteries are covered by a 3-month warranty against manufacturing faults only
This does NOT cover:
- Battery degradation over time
- Reduced battery health
- Normal wear and usage
Battery Health Notice
- Devices are tested and supplied with 85–90% battery health (unless otherwise stated)
- Battery performance will vary depending on:
- Usage habits
- App activity
- Device settings
For customers with high-usage requirements, we strongly recommend contacting us before purchase so we can advise on a suitable device.
Manufacturer Warranty Disclaimer
Products may include a manufacturer warranty; however:
- This is not guaranteed
- It may depend on activation date, region, or manufacturer policy
- We are not responsible for manufacturer warranty claims
For security and fraud prevention, all devices are sold with their IMEI and serial numbers recorded.
If a returned device does not match our records, we will not accept responsibility and reserve the right to blacklist the device and report it.
We take fraud prevention seriously and cooperate with law enforcement where required.
Same Day Dispatch
12 Months Warranty
Quality Guaranteed
