---
product_id: 698387382
title: "In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK"
brand: "in phase"
price: "€ 259.77"
currency: EUR
in_stock: true
reviews_count: 13
category: "In Phase"
url: https://www.desertcart.hr/products/698387382-in-phase-usw300-underseat-subwoofer-car-subwoofer-with-built-in
store_origin: HR
region: Croatia
---

# Compact 16x5x5 cm design 300W max power punch Die-cast aluminum chassis In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK

**Brand:** in phase
**Price:** € 259.77
**Availability:** ✅ In Stock

## Summary

> 🎶 Unleash pro-grade bass without sacrificing space or style!

## Quick Answers

- **What is this?** In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK by in phase
- **How much does it cost?** € 259.77 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/products/698387382-in-phase-usw300-underseat-subwoofer-car-subwoofer-with-built-in)

## Best For

- in phase enthusiasts

## Why This Product

- Trusted in phase brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Remote Bass Control:** Tune your bass on the fly with an intuitive remote—no more awkward adjustments behind the seat.
- • **Powerful 300W Output:** Feel every beat with a built-in amplifier delivering up to 300 watts of pure bass energy.
- • **Discreet Underseat Fit:** Sleek, compact design fits seamlessly under your car seat for a clean, professional install.
- • **Heavy-Duty Metal Build:** Die-cast aluminium chassis guarantees zero flex and maximum durability under pressure.
- • **Rattle-Free Aluminium Cone:** Lightweight yet robust aluminium cone with damping tech ensures deep, distortion-free bass.

## Overview

The In Phase USW300 is a UK-designed, compact underseat subwoofer featuring a powerful 300W built-in amplifier and a durable die-cast aluminium chassis. Its aluminium cone with integrated damping delivers deep, rattle-free bass, while the compact form factor fits discreetly under car seats. Complete with remote control for easy tuning, this subwoofer transforms your car audio experience with professional-grade sound and robust build quality.

## Description

From the manufacturer Beautiful design, big performance The key thing about the In Phase USW 300 is the performance, the little active woofer really packs a punch, the bass response is amazing and you really do get SUB Bass from it. Its extremely responsive so the music has a completely different sound once added to the car.

Review: Fantastic value for money, easy to install. - + Great Sound, Great Quality, Easy to Install, Fantastic Value. - No RCA Leads. This is a great little sub if you’re after a fuller sound for your car. I installed a set of component speakers into a Kangoo van and was disappointed with the bass, so I fitted this and it’s made a massive difference! It’s a substantial well built item and has all the sound controls on the remote instead of fiddly dials on the back of the unit which makes it great to tune while it’s situ without messing around accessing it again. It comes with all the leads you need to get it running via high level input, but you will need to but a phono lead if you want to connect it via low level RCA.
Review: Great subwoofer - Great sound, full kit included for install, you might want to watch a few YouTube videos on how to install. Fits under the passenger seat so perfect size, 10/10 and glad I went with the British design over my usual choice of Pioneer for anything sound

## Features

- Subwoofer for Car - With a built in amplifier, max output of 300 W and 150 W RMS, the In Phase USW300 is a true pocket powerhouse of audio performance.
- Coned Aluminium Active Subwoofer Car - Aluminium Cones are light in weight and can be really stiff, but they are really robust cones that rarely go wrong. This sub has a damping material built into its cone and spider to ensure a rattle-free performance and deep bass
- Heavy duty durable construction - Die Cast Aluminium Chassis - no plastic structure here. The metal body is part of a secure and rigid structure, no flexing body when the unit is in full power, this also helps with bass output.
- Compact and discrete - Allowing to install the USW300 anywhere within vehicles boot, under seats, behind seats or in the foot well
- Trusted Brand - In Phase is a UK based brand, our team currently has over 500 years of audio research and development experience, creating quality products from premium material that our customer deserve, including, car audio speakers & subwoofers.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B089GZ6F14 |
| Age Range Description | Adult |
| Antenna Location | Car |
| Audio Driver Size | 8 Inches |
| Audio Driver Type | Dynamic Driver |
| Audio Output Mode | Stereo |
| Audio output mode | Stereo |
| Best Sellers Rank | 2,768 in Electronics & Photo ( See Top 100 in Electronics & Photo ) 1 in Car Enclosed Subwoofer Systems |
| Box Contents | Car Subwoofer Active Enclosure, Wiring Kit, Mounting Brackets, Remote Controller, Instruction Manual |
| Brand | In Phase |
| Brand Name | In Phase |
| Colour | USW300 |
| Compatible Devices | Desktop |
| Compatible with Vehicle Type | Car |
| Connectivity Protocol | Auxiliary |
| Connectivity technology | Auxiliary |
| Control Method | Remote |
| Controller Type | Remote Control |
| Country of Origin | China |
| Customer Package Type | Standard packaging |
| Customer Reviews | 4.4 out of 5 stars 566 Reviews |
| EU Spare Part Availability Duration | 2 Years |
| Enclosure Material | Aluminum/Die Cast Aluminum |
| Frequency Response | 150 Hz |
| Frequency response | 150 Hz |
| Global Trade Identification Number | 05060047672757 |
| Input Voltage | 12 Volts |
| Input voltage | 12 Volts |
| Is Waterproof | false |
| Item Dimensions D x W x H | 5D x 16W x 5H centimetres |
| Item Type Name | Underseat Active Subwoofer |
| Item Weight | 1.5 Kilograms |
| MP3 player | No |
| Manufacturer | In Phase |
| Maximum Speaker Output Power (in watts) | 300 Watts |
| Model Name | USW300 |
| Model Number | USW300 |
| Mounting Type | Underseat Mount |
| Network Connectivity Technology | Auxiliary |
| Number of Audio Channels | 2.0 |
| Number of Items | 1 |
| Power Source | Corded Electric |
| Product Features | Built-in Amplifier, Aluminium Coned Subwoofer |
| Speaker Size | 28 Centimetres |
| Speaker Type | Subwoofer |
| Speaker maximum output power | 300 Watts |
| Specific Uses For Product | Car |
| Subwoofer Connectivity Technology | Wired |
| Tweeter Diameter | 1 Inches |
| Warranty Type | Limited |
| Wireless Technology Type | No Wireless Communication Technology |
| Woofer Driver Diameter | 200 Millimetres |

## Product Details

- **Audio output mode:** Stereo
- **Brand:** In Phase
- **Connectivity technology:** Auxiliary
- **Frequency response:** 150 Hz
- **Input voltage:** 12 Volts
- **Material:** Aluminum/Die Cast Aluminum
- **Model name:** USW300
- **Mounting type:** Underseat Mount
- **Speaker maximum output power:** 300 Watts
- **Speaker type:** Subwoofer

## Images

![In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK - Image 1](https://m.media-amazon.com/images/I/81u+V61e6lL.jpg)
![In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK - Image 2](https://m.media-amazon.com/images/I/81owuQyFHpL.jpg)
![In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK - Image 3](https://m.media-amazon.com/images/I/81iZdsvGaHL.jpg)
![In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK - Image 4](https://m.media-amazon.com/images/I/81btOIGOUaL.jpg)
![In Phase USW300 Underseat Subwoofer | Car Subwoofer with Built in Amplifier | 300W Active Subwoofer Car | Compact Design Under Seat Subwoofer Car | Heavy Duty Durable Construction | Designed in the UK - Image 5](https://m.media-amazon.com/images/I/81pWgGBkvHL.jpg)

## Available Options

This product comes in different **Style** options.

## Questions & Answers

**Q: Does this require two connections? One rca from the unit to the sub out connection on headunit. And one to battery?**
A: Yes, it needs 12v power, you need the audio connection from the head unit ( RCA/sub out ) permanent live to the battery and earth to the chassis or battery, then the remote wire to the head unit which tells the sub to turn on and off, all aftermarket head units have a remote live connection for this purpose 👍

**Q: Can i use it in my home system? I have a musical fidelity amp and Linn speakers**
A: Yes, however you would need a 12V transformer with 20amps current supply.

**Q: how do you turn off if connected straight to battery?**
A: It detects the audio signal and turns itself on and off when you turn your head unit on/off. It's clever like that :-)

**Q: Can I wire to cigarette lighter for power? Says max 120w**
A: You cannot. You need to wire the active subwoofer directly for power to the battery Positive. If you are unsure how to do this, many videos on Youtube. It also explains in the instructions. However we always recommend professional installation if you are not sure.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Fantastic value for money, easy to install.
*by A***M on 17 February 2025*

+ Great Sound, Great Quality, Easy to Install, Fantastic Value. - No RCA Leads. This is a great little sub if you’re after a fuller sound for your car. I installed a set of component speakers into a Kangoo van and was disappointed with the bass, so I fitted this and it’s made a massive difference! It’s a substantial well built item and has all the sound controls on the remote instead of fiddly dials on the back of the unit which makes it great to tune while it’s situ without messing around accessing it again. It comes with all the leads you need to get it running via high level input, but you will need to but a phono lead if you want to connect it via low level RCA.

### ⭐⭐⭐⭐⭐ Great subwoofer
*by L***M on 10 May 2026*

Great sound, full kit included for install, you might want to watch a few YouTube videos on how to install. Fits under the passenger seat so perfect size, 10/10 and glad I went with the British design over my usual choice of Pioneer for anything sound

### ⭐⭐⭐⭐ Great value, this does the job.
*by A***. on 9 February 2022*

For the price I can't complain. This does the job if you want to add a little low end and space is limited. It's not too difficult to install if you understand basic wiring. The sound quality isn't audiophile but it will improve any standard set up that lacks the low end. It has an adjustable crossover and gain controls on the unit itself, and an additional remote volume control. What's more it fits neatly under most car seats. You don't need to buy any additional equipment to get this going, all the wiring is also provided. Ok so maybe the bass isn't very tight, it's not going to compare to a 12 inch sub box booming insane levels of bass in your boot but it's an underseat space saving 6" woofer with a built-in amp (active) for less than £150, it is a massive improvement to standard car speakers. Personally I dial the crossover from my head unit (car stereo) as it has a sub out, this will give better results but you can use your factory stereo and wire in using the speaker connections on the back. It's never going to compete with a proper sub but it's nice and compact and provides the extra bass I was missing without breaking the bank. Edit: I've been using this unit for a while now and no complaints. I actually take the longer way home so I can enjoy the music 🎶

## Frequently Bought Together

- In Phase USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier
- In Phase XTC17.2 250W 2 x 6.5 Inch Car Speakers - 17cm Car Speaker for Door or Parcel Shelf - Audio Speakers & Subwoofers

---

## Why Shop on Desertcart?

- 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016
- 🌍 **Shop Globally** — Access 737+ million products across 21 categories
- 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price
- 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members)
- 🔒 **Secure Payments** — Trusted payment options with buyer protection
- ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews

**Shop now:** [https://www.desertcart.hr/products/698387382-in-phase-usw300-underseat-subwoofer-car-subwoofer-with-built-in](https://www.desertcart.hr/products/698387382-in-phase-usw300-underseat-subwoofer-car-subwoofer-with-built-in)

---

*Product available on Desertcart Croatia*
*Store origin: HR*
*Last updated: 2026-07-14*