---
product_id: 698387382
title: "USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier"
brand: "in phase"
price: "$320.98"
currency: USD
in_stock: true
reviews_count: 12
category: "In Phase"
url: https://www.desertcart.us/products/698387382-usw300-300w-underseat-subwoofer-active-car-subwoofer-with-built-in
store_origin: US
region: United States of America
---

# Compact 16cm width 300W max power Die-cast aluminum chassis USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier

**Brand:** in phase
**Price:** $320.98
**Availability:** ✅ In Stock

## Summary

> 🎶 Elevate your drive with bass that commands attention!

## Quick Answers

- **What is this?** USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier by in phase
- **How much does it cost?** $320.98 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/698387382-usw300-300w-underseat-subwoofer-active-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

- • **Powerful 300W Output:** Feel every beat with a max output that transforms your car audio experience.
- • **Heavy-Duty Metal Build:** Die-cast aluminum chassis delivers durability and vibration-free performance.
- • **Discreet Underseat Design:** Fits seamlessly under seats or in tight spaces without sacrificing sound quality.
- • **Rattle-Free Aluminium Cone:** Lightweight yet robust cone design ensures deep, distortion-free bass.
- • **Remote Control Convenience:** Fine-tune your bass on the fly with an easy-access remote, no more awkward adjustments.

## Overview

The In Phase USW300 is a compact, active underseat subwoofer delivering up to 300W max power through a robust die-cast aluminum chassis and lightweight aluminium cone. Designed for easy installation in tight vehicle spaces, it offers rattle-free deep bass and remote control tuning, making it a premium choice for audiophiles seeking powerful, discreet car audio enhancement.

## Description

Free delivery and returns on eligible orders. Buy In Phase USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier at desertcart UK.

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
Review: Compact sub with a great sound - I was a little sceptical before ordering and was considering building something to go under the floor in my SLK. However I purchased one to try and was not disappointed. I fitted under the floor in the passenger side footwell on an SLK, some models have an amp fitted there. At the same time I replaced the headunit with a powered android type with CarPlay. Fitting was easy as the Android head had cables to connect to and a sub output. The remote was remotes to the side of the centre console, convenient for adjustments should I need to. Build quality is good, sound quality is excellent for a compact sub of its size it compliments the rest of the speaker system. It was actually worth spending the money on this product, if you can’t get a big box in anywhere this is the ideal choice and with the remote just adds to the functionality, to be fair I’ve not had the need to alter it from the initial twiddling. I’ve written this after purchasing in August 2024, just in Dec 2025 now and still enjoying the sub!

## 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 |
| Box Contents | Car Subwoofer Active Enclosure, Wiring Kit, Mounting Brackets, Remote Controller, Instruction Manual |
| Brand Name | In Phase |
| Colour | USW300 |
| Compatible Devices | Desktop |
| Compatible with Vehicle Type | Car |
| Connectivity Protocol | Auxiliary |
| Control Method | Remote |
| Controller Type | Remote Control |
| Country of Origin | China |
| Customer Package Type | Standard packaging |
| Customer Reviews | 4.4 4.4 out of 5 stars (549) |
| EU Spare Part Availability Duration | 2 Years |
| Enclosure Material | Aluminum/Die Cast Aluminum |
| Frequency Response | 150 Hz |
| Global Trade Identification Number | 05060047672757 |
| 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 | Amplifier |
| Speaker Size | 28 Centimetres |
| Speaker Type | Subwoofer |
| 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

![USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier - Image 1](https://m.media-amazon.com/images/I/81u+V61e6lL.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

### ⭐⭐⭐⭐⭐ 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

### ⭐⭐⭐⭐⭐ Compact sub with a great sound
*by D***H on 2 December 2025*

I was a little sceptical before ordering and was considering building something to go under the floor in my SLK. However I purchased one to try and was not disappointed. I fitted under the floor in the passenger side footwell on an SLK, some models have an amp fitted there. At the same time I replaced the headunit with a powered android type with CarPlay. Fitting was easy as the Android head had cables to connect to and a sub output. The remote was remotes to the side of the centre console, convenient for adjustments should I need to. Build quality is good, sound quality is excellent for a compact sub of its size it compliments the rest of the speaker system. It was actually worth spending the money on this product, if you can’t get a big box in anywhere this is the ideal choice and with the remote just adds to the functionality, to be fair I’ve not had the need to alter it from the initial twiddling. I’ve written this after purchasing in August 2024, just in Dec 2025 now and still enjoying the sub!

### ⭐⭐⭐⭐ 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

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*Product available on Desertcart United States of America*
*Store origin: US*
*Last updated: 2026-05-16*