---
product_id: 436348969
title: "In Phase Car Audio XTB-828R 8\" 400W Active Subwoofer with Passive Radiator and Class D Amplifer , Black | 8\" 20cm Active Subwoofer for Car | Car Audio Speakers & Subwoofers | Sub Woofer Speakers | Black Car Bass sub woofer speakers"
brand: "in phase"
price: "€ 303.47"
currency: EUR
in_stock: true
reviews_count: 13
url: https://www.desertcart.sk/products/436348969-in-phase-car-audio-xtb-828r-8-400w-active-subwoofer
store_origin: SK
region: Slovakia
---

# 300W peak Class D amplifier Compact desktop-sized design 8-inch glass fiber cone In Phase Car Audio XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer , Black | 8" 20cm Active Subwoofer for Car | Car Audio Speakers & Subwoofers | Sub Woofer Speakers | Black Car Bass sub woofer speakers

**Brand:** in phase
**Price:** € 303.47
**Availability:** ✅ In Stock

## Summary

> 🎶 Elevate your drive with bass that commands attention — compact power, colossal impact!

## Quick Answers

- **What is this?** In Phase Car Audio XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer , Black | 8" 20cm Active Subwoofer for Car | Car Audio Speakers & Subwoofers | Sub Woofer Speakers | Black Car Bass sub woofer speakers by in phase
- **How much does it cost?** € 303.47 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.sk](https://www.desertcart.sk/products/436348969-in-phase-car-audio-xtb-828r-8-400w-active-subwoofer)

## 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

- • **Space-Savvy Design:** Compact footprint fits discreetly in your car boot, maximizing bass without sacrificing cargo space.
- • **Powerful Yet Efficient:** Class D amplifier delivers up to 300W peak power without draining your car’s battery.
- • **Precision Bass Mastery:** Experience deep, controlled bass with a purpose-built glass fiber cone and passive radiator technology.
- • **Seamless Compatibility:** High and low-level inputs work effortlessly with both aftermarket and OEM head units.
- • **Plug & Play Convenience:** Comes complete with wiring kit and remote bass gain control for instant, customizable sound upgrades.

## Overview

The In Phase Car Audio XTB-828R is an 8-inch active subwoofer featuring a lightweight, durable glass fiber cone paired with a passive radiator for superior bass accuracy. Powered by a built-in 300W peak Class D amplifier, it offers deep, controlled low frequencies in a compact, desktop-sized enclosure that fits easily in your car boot. Compatible with OEM and aftermarket head units via high and low-level inputs, it includes a wiring kit and remote bass control, making it a powerful yet space-efficient upgrade for any car audio enthusiast.

## Description

XTB-828R is a passive radiator equipped active sealed subwoofer enclosure. Hit really low frequencies and experience true bass accuracy not normally found in bog-standard active subwoofer. Equipped with an all-weather glass fiber woven cone 20cm (8') drive unit, paired with a passive radiator in sealed enclosure technology, it provides deep and controlled bass frequencies. Its built-in 300W class D amplifier offers high power handling and numerous controls.
XTB-828R has high and low-level inputs that can be plugged with after market and OEM head units. This four-in-one enclosure reduces overall dimensions while offering a great bass level. This comes complete with a wiring kit apart from RCA cables. If fitting to an aftermarket head unit, you will need RCA cables.
A robust, compact and efficient Class D amplifier is mounted to this enclosure. This is the driving force behind the sub. Only the finest components in it's category will do. Offering up to 300W peak and 200W RMS Power.
This sub is only the size of a small desktop computer case. This small footprint allows the user to add thumping bass without compromising space in the boot.
The glass fibre subwoofer cone is purpose-built for this package, it is lightweight, durable and rigid without compromising sound quality. A lot of market leaders have a generic subwoofer (from their range) then they build a box to suit. Which works to an extent, this package offers you something more unique and performance based.

## Features

- PASSIVE RADIATOR: a speaker with no voice coil or magnet, basically a speaker cone. This is not connected to the amp at all
- COMPACT DESIGN: This sub is only the size of a small desktop computer case. This small footprint allows the user to add thumping bass without compromising space in the boot
- SUPERIOR SUBWOOFER CONE: The glass fibre subwoofer cone is purpose built for this package, it is lightweight, durable and rigid without compromising sound quality
- Power Source Type: Corded Electric

## Technical Specifications

| Specification | Value |
|---------------|-------|
| Antenna Location | car |
| Asin | B09ZPMVHCV |
| Audio Driver Size | 8 Inches |
| Audio Driver Type | Dynamic Driver |
| Audio Output Mode | Stereo |
| Best Sellers Rank | 91,228 in Electronics & Photo (See Top 100 in Electronics & Photo) 58 in Car Enclosed Subwoofer Systems |
| Box Contents | All Cables Included, Remote Bass Gain |
| Brand Name | In Phase |
| Colour | Black |
| Compatible Devices | Personal Computer |
| Connectivity Protocol | RCA |
| Control Method | Voice |
| Controller Type | Remote Control |
| Customer Reviews | 4.0 4.0 out of 5 stars (38) 4.0 out of 5 stars |
| Enclosure Material | Metall/Kunststoff |
| Is Waterproof | False |
| Item Dimensions D X W X H | 5D x 16W x 5H centimetres |
| Item Type Name | Car Speakers |
| Manufacturer | In Phase |
| Maximum Speaker Output Power In Watts | 300 Watts |
| Model Name | In Phase XTB-828R |
| Model Number | XTB-828R |
| Mounting Type | Car Mount |
| Network Connectivity Technology | RCA |
| Number Of Audio Channels | 2.0 |
| Number Of Items | 1 |
| Power Source | Corded Electric |
| Product Features | Passive Radiator |
| Product Warranty | 1 Year |
| Speaker Size | 8 Inches |
| Speaker Type | Subwoofer |
| Specific Uses For Product | Car Audio |
| Subwoofer Connectivity Technology | Wired |
| Tweeter Diameter | 1 Inches |
| Warranty Type | Limited |
| Water Resistance Level | Waterproof |
| Wireless Technology Type | No Wireless Communication Technology |
| Woofer Driver Diameter | 8 Inches |

## Product Details

- **Audio output mode:** Stereo
- **Brand:** In Phase
- **Connectivity technology:** RCA
- **Material:** Metall/Kunststoff
- **Model name:** In Phase XTB-828R
- **Mounting type:** Car Mount
- **Recommended uses for product:** car
- **Speaker maximum output power:** 300 Watts
- **Speaker type:** Subwoofer
- **Special feature:** Passive Radiator

## Images

![In Phase Car Audio XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer , Black | 8" 20cm Active Subwoofer for Car | Car Audio Speakers & Subwoofers | Sub Woofer Speakers | Black Car Bass sub woofer speakers - Image 1](https://m.media-amazon.com/images/I/91W4PNuYh1L.jpg)

## Questions & Answers

**Q: How is this wired up pls**
A: you need to buy audio cables (red and black) they go to your stereo. The blue wire also to stereo. 12v from positive battery. And 0v (ground) to negative battery

**Q: Is the wiring included lilke as advised**
A: Yes all the wires were included if ever a mistake was made I would still recommend this is very reliable strongly built and gives good bass that 10x it's size

## Customer Reviews

### ⭐⭐⭐⭐⭐ Boomy compact subwoofer.
*by  on Reviewed in the United Kingdom 18 July 2023*

Was looking to add bass to my little Suzuki Alto. As you can imagine the original two 4inch paper speakers were inadequate, so added a pair of Vibe 4inch 2way components and a pair of 6x9 which dramatically improved sound quality. However deep bass was missing and since space was a premium was looking for a compact subwoofer.The In-phase XTB828R certainly provides decent bass for the size and price. Considering it's an 8inch sub with a passive sound radiator, and comes with all the necessary wiring, you can't go wrong.One thing to note when I first installed it, the bass seemed underwhelming i.e. not loud. But adjusting the output gain from my head unit sorted that out (Not the same as volume!).Overall a decent sub to add some bass. Wont shake any windows but hey I think it works best in a small car. If you you have a normal sized car you would need a 12inch sub ;)

### ⭐⭐⭐⭐⭐ Excellent Sub!
*by  on Reviewed in the United Kingdom 7 February 2024*

I have been using this now for almost a year, anyone saying this sub is underwhelming just have not configured it right as this thing can really rumble, the auto on feature is the reason i got this one due to not being able to access the necessary cables due to array of other devices the vehicle already has onboard but with the right amp and crossover this sounds incredible and I would highly recommend.

### ⭐⭐⭐⭐ 3 years so far, no problems
*by  on Reviewed in the United Kingdom 28 January 2026*

Ok, I have had this for 3 years now,I have this in my off grid cabin connected to a kenwood head unit.Its size is good for me as fits nicely behind the sofa. Considering the size, the bass is quite good. No problems with it in 3 years and is used most days.

## Frequently Bought Together

- In Phase Car Audio XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer , Black
- VIBE Audio Slick 1500 W System Car Wiring Kit

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*Product available on Desertcart Slovakia*
*Store origin: SK*
*Last updated: 2026-08-17*