---
product_id: 698387382
title: "In Phase USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier"
brand: "in phase"
price: "1309 zł"
currency: PLN
in_stock: true
reviews_count: 8
category: "In Phase"
url: https://www.desertcart.pl/products/698387382-in-phase-usw300-300w-underseat-subwoofer-active-car-subwoofer-built
store_origin: PL
region: Poland
---

# Compact 16x5x5 cm size 300W max power output Die-cast aluminum chassis In Phase USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier

**Brand:** in phase
**Price:** 1309 zł
**Availability:** ✅ In Stock

## Summary

> 🚗💥 Unleash epic bass without sacrificing space or style!

## Quick Answers

- **What is this?** In Phase USW300 300W Underseat Subwoofer - Active Car Subwoofer with Built-in Amplifier by in phase
- **How much does it cost?** 1309 zł with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.pl](https://www.desertcart.pl/products/698387382-in-phase-usw300-300w-underseat-subwoofer-active-car-subwoofer-built)

## 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

- • **Durable Metal Build:** Engineered with a die-cast aluminum chassis for zero flex and maximum bass resonance—no plastic compromises here.
- • **Discreet Underseat Design:** Sleek, compact form factor fits seamlessly under your car seat or in tight spaces, keeping your cabin clutter-free and stylish.
- • **Rattle-Free Aluminium Cone:** Experience crystal-clear lows with lightweight yet ultra-stiff aluminum cones featuring damping materials to eliminate distortion.
- • **Remote Control Convenience:** Fine-tune your bass levels on the fly with an intuitive remote, so you never miss a beat or have to reach awkwardly.
- • **Powerhouse Bass Performance:** Feel every beat with a robust 300W max output and 130W RMS amplifier built-in for deep, rich bass that transforms your drive.

## Overview

The In Phase USW300 is a compact, active underseat subwoofer delivering powerful 300W max output through a built-in amplifier. Its robust die-cast aluminum chassis and aluminum cone driver ensure durable, rattle-free deep bass. Designed for easy installation in tight vehicle spaces, it includes a remote control for effortless sound tuning, making it the perfect upgrade for millennial professionals seeking premium car audio without bulk.

## 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: 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: 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

- Rich powerful base - With a built in amplifier, max output of 300 W and 130 W RMS, the In Phase USW300 is a true pocket powerhouse of audio performance
- Aluminium coned subwoofer - 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, Undersea, behind seat and foot wells

## 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 |
| 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 | aids |
| 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 483 Reviews |
| 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 |
| Item height | 5 centimetres |
| MP3 player | No |
| Manufacturer | In Phase |
| Maximum Speaker Output Power (in watts) | 300 Watts |
| Model Name | USW300 |
| Model Number | USW300 |
| Mounting Type | Underseat attachment |
| 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 |
| 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 |

## 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 attachment
- **Speaker maximum output power:** 300 Watts
- **Speaker type:** Subwoofer

## Images

![In Phase 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

### ⭐⭐⭐⭐⭐ 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.

### ⭐⭐⭐⭐⭐ 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 Poland*
*Store origin: PL*
*Last updated: 2026-01-23*