If you are new to high-end audio, welcome. You are about to learn about one of the most rewarding upgrades you can make to a music or home theater system, and you will learn it without needing a dictionary of technical jargon. The REL Acoustics T/9x is a subwoofer, and by the end of this guide you will understand exactly what that means, how it works, and whether it is right for you.
What is the REL Acoustics T/9x?
The REL Acoustics T/9x is an active subwoofer, which is a speaker designed to reproduce the lowest, deepest sounds that regular speakers struggle to produce. The word "active" simply means it has its own built-in amplifier, so it powers itself rather than borrowing power from your main amplifier. Think of it as a specialist. Your main speakers handle voices, guitars, and cymbals beautifully, while the T/9x takes care of the deep foundation underneath: the rumble of a film explosion, the weight of an upright bass, the low notes of an organ.
Where does a subwoofer fit in my system?
A subwoofer sits alongside your existing speakers and fills in the deep bass they cannot reach on their own. You place it on the floor, usually near the front of the room, and connect it to your amplifier or receiver. REL is well known for a philosophy where the subwoofer supports the entire system, not just movie effects. That means the T/9x is designed to make your music sound fuller and more lifelike, as well as making movies more exciting. It works with two-channel stereo setups and with surround sound home theater systems alike.
How the T/9x Makes Sound
What does "closed design with passive radiator" mean?
It means the T/9x uses a sealed cabinet paired with a second, unpowered driver to produce clean, tight, and deep bass. Here is the plain version. Inside the sealed box is the main driver that does the work. The passive radiator is a second cone that has no motor of its own. Instead, it is moved by the air pressure created inside the sealed cabinet. This design helps the subwoofer reach lower and play with more authority than the box size alone would suggest, while keeping the bass controlled rather than boomy.
What is the active driver?
The active driver is a 10 inch (250mm) long-throw, forward-firing cone, and it is the part that actually generates the bass you hear. "Long-throw" means the cone can move in and out a long way, which lets it push more air and produce deeper notes. "Forward-firing" means it points out toward the room, aimed at you.
What does the passive radiator do?
The passive radiator is a 12 inch (300mm) down-firing cone that reinforces the deep bass without needing its own power. It faces downward toward the floor. Because it is larger than the active driver and responds to the pressure inside the cabinet, it adds extra depth and richness to the lowest notes, extending what the subwoofer can do.
How powerful is the built-in amplifier?
The T/9x has a Class A/B amplifier rated at 300 watts RMS, which gives it plenty of muscle to drive the bass cleanly in typical rooms. "Class A/B" refers to a proven amplifier design known for musical, natural sound. "RMS" is the honest, continuous power rating, meaning the amp can deliver that power steadily rather than just in brief bursts. In everyday listening, this means the T/9x has the headroom to stay composed during demanding passages without straining.
How deep can it go?
The T/9x reaches down to 27Hz at -6dB, which is very deep bass that you feel as much as hear. To put that in context, human hearing generally starts around 20Hz at the very bottom. The "-6dB" part is simply the standard way engineers describe how deep a subwoofer plays before the sound gently rolls off. In practical terms, 27Hz covers the vast majority of low notes in music and the deep effects in films.
The Connections and Controls
How do I connect the T/9x to my system?
The T/9x offers three ways to connect: a high-level Speakon input, a low-level RCA input, and a .1/LFE RCA input. The high-level Speakon connection is the one REL is famous for. It takes a feed from the same terminals that power your main speakers, which helps the subwoofer match the character and timing of your speakers so the bass blends seamlessly. The low-level RCA input is a more conventional connection used with many amplifiers and receivers. The .1/LFE RCA input is designed for home theater, connecting to the dedicated subwoofer output on a surround sound receiver.
Can I use the T/9x without wires?
Yes, the T/9x is compatible with the optional REL Arrow wireless system, which lets you place the subwoofer without running a cable across the room. This is helpful when the best spot for bass is not near your amplifier. The Arrow system is an add-on, so it is not included in the box, but the T/9x is ready to work with it.
What does the crossover control do?
The continuously variable crossover sets the point where the subwoofer takes over from your main speakers. "Continuously variable" means you can adjust it smoothly to any setting rather than choosing from a few fixed options. Turning it lets you decide how much of the deep bass the T/9x handles, so it hands off cleanly to your speakers without doubling up or leaving a gap.
What do the gain controls do?
The gain controls set how loud the subwoofer plays relative to your main speakers, and the T/9x provides separate gain for the high-level and .1/LFE connections. "Gain" is simply the volume of the subwoofer. Having independent controls means you can dial in the right level for music through the high-level input and a separate level for movies through the .1/LFE input, so both sound balanced.
What is the phase switch for?
The phase switch makes sure the subwoofer and your main speakers push air in the same direction at the same time, so their bass adds together instead of canceling out. If the bass ever sounds thin or hollow, flipping the phase switch is a quick way to correct it and restore full, satisfying low end.
Build, Design, and Who It Is For
Why does REL Acoustics build quality matter?
REL Acoustics has built its reputation on subwoofers designed specifically to blend with music, and that care shows in the T/9x. The cabinet is finished in either high-gloss black or high-gloss white, both of which look at home in a living space rather than hidden away. The attention to the driver design, the amplifier, and the connection options all reflect REL's focus on musical accuracy, not just raw volume. Good build quality means the subwoofer stays clean and controlled, which is exactly what allows it to disappear into your system so you hear music and film, not the box itself.
How big is it and where will it fit?
The T/9x measures 14.9 x 14.2 x 15.3 inches (380 x 361 x 390mm) including its feet and weighs approximately 37.5 lbs (17 kg). That is a compact footprint, roughly the size of a small end table, so it fits comfortably in most rooms without dominating the space. The solid weight for its size reflects the careful cabinet construction that keeps unwanted vibration under control.
Who is the T/9x best suited to?
The T/9x suits someone who wants serious, musical bass in a real-world room without needing an enormous subwoofer. It is an excellent match for a quality stereo system where you want music to sound complete, and it is equally at home in a home theater thanks to its .1/LFE input. If you are new to high-end audio and want a subwoofer that is flexible, well built, and designed to blend naturally with your existing speakers, the REL Acoustics T/9x is a welcoming and rewarding place to begin.