In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer

In Phase

In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer

Reviewed byUpdated 4 Jun 2026

Best price available

£99.99

From £99.99 across 1 merchant
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 fibre 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 400W 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 headunits. 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 headunit, you will need RCA cablesWhat on Earth is a 'passive radiator'?A Passive Radiator is a speaker with no voice coil or magnet, basically a speaker cone. This is not connected to the amp at all. The purpose of this speaker is to allow the trapped sound pressure in the sealed enclosure to excite a resonance that makes it easier for the speaker system to create the deepest pitches (e.g bassline). In short, it gives you the benefit of ported enclosures without the downsides. This leads to better sound quality, with a linear frequency response of the sealed cabinet and the higher output you get from a ported design. This is also achieved in a smaller size than the ported subwoofer. You also do not have the same issues with port noise, and instead, you end up with a smooth bass.Class D AmplifierA 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 400W peak and 200W RMS PowerCompact DesignThis 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 ConeThe 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 .Car Audio Centre Manager Comments'Even by In Phase Standards this is unprecedented, unique and absurdly amazing. Passive Radiator technology in this application just makes sense. I am struggling to understand why the big players like Alpine, Pioneer, Kenwood, JVC, Focal or JL Audio haven't jumped on this trend'

Price Analysis

Fair Price

The current price is around the average. It's a reasonable time to buy.

Current Best

£99.99

Average Price

£99.99

Lowest Ever

Highest Ever

Compare Prices (1 merchant)

Compare prices for In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer

Ca

Car Audio Centre

Best Price
In Stock

Price

£99.99

Shipping

Total

£99.99
Go to Store

Price Alert

Get notified when the price drops. No account required.

Get a price drop alert
£

Current best price: £99.99

Product Details

BrandIn Phase
MerchantCar Audio Centre
GTIN5060801411080
MPN82996

Frequently Asked Questions

What is the best price for In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer?+
The best price for In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer is currently £99.99 from Car Audio Centre. We compare prices across 1 merchant to find you the lowest price.
How do I get notified when In Phase XTB-828R 8" 400W Active Subwoofer with Passive Radiator and Class D Amplifer drops in price?+
You can set a free price alert on this page — just enter your email and your target price. We'll email you as soon as the price drops to that level. No account needed.
Is In Phase a good brand?+
We compare In Phase products across multiple UK merchants to help you find the best deals. Check our In Phase brand page for more products and price comparisons.

How we make money

OrganicDiscount is free to use. When you click a link to a merchant and make a purchase, we may earn a small affiliate commission at no extra cost to you. This helps us keep the site running and continue comparing prices across UK retailers. Our rankings and recommendations are never influenced by commission — we always show the lowest price first.