If you are new to high-end audio, walking into the world of subwoofers can feel a little overwhelming. There is a lot of jargon, and not all of it is explained in plain terms. This guide is here to fix that. We are going to walk through the REL Acoustics HT/1205 MKII from top to bottom, in warm and clear language, so you understand exactly what it is, what every button and connector does, and whether it belongs in your room.
What is the REL Acoustics HT/1205 MKII?
The HT/1205 MKII is an active home theater subwoofer built to deliver the deep bass in movies and games. "Active" simply means it has its own built-in amplifier, so it powers itself rather than borrowing power from your receiver. It belongs to REL Acoustics' HT Series, which is a line designed specifically with home theater in mind. In practical terms, this is the box that handles explosions, rumbles, deep sound effects, and the low end that you feel in your chest as much as you hear it.
Where does a subwoofer fit in a home theater system?
A subwoofer sits alongside your other speakers and takes over the lowest frequencies that regular speakers struggle to reproduce. Your main speakers handle voices, instruments, and most of the action, but the very deepest sounds require a driver built for the job. The HT/1205 MKII fills in that bottom octave, giving your system a fuller, more cinematic feel. Think of it as the foundation of the room's sound rather than a standalone piece.
The Driver and Amplifier: The Heart of the Sub
What does the 12 inch long throw driver do?
The HT/1205 MKII uses a 12 inch (300mm) long throw, forward firing driver, which is the cone you can see moving that pushes air to create bass. "Long throw" means the cone can travel a good distance in and out, which lets it move a lot of air. Moving air is exactly how you get deep, powerful bass. "Forward firing" means the driver points out the front of the cabinet toward the room, sending its energy directly into your listening space.
What does "forward firing" mean for placement?
Forward firing simply describes the direction the driver faces, which is straight ahead rather than down at the floor or off to the side. Day to day, this gives you a clear, direct sense of where the bass is coming from and makes the sub easy to reason about when you position it. You point the business end toward the room and let it do its work.
How powerful is the amplifier?
The HT/1205 MKII has a Class D amplifier rated at 500 watts RMS. That number tells you how much continuous power the sub can produce. RMS is a real world, sustained measurement rather than a brief peak, so 500 watts RMS is a meaningful, dependable figure. In everyday use, this means the sub has plenty of headroom to hit hard during big movie moments without straining.
What is a Class D amplifier and why does it matter?
Class D refers to the type of amplifier design inside the sub, and it is known for being efficient and running cool. That efficiency lets a compact cabinet produce a lot of power without generating excessive heat or wasting energy. For you, this translates to strong, reliable bass from a manageable box that you can live with day after day.
Connections: How the HT/1205 MKII Talks to Your System
What is the Low-level RCA input for?
The Low-level RCA input is a standard connection that accepts a signal from your receiver or processor using a familiar RCA cable. "Low-level" means it takes a line-level signal, which is the same kind of signal that travels between most home audio components. This is a common, easy way to connect the sub, and if you have used RCA cables before, this will feel completely natural.
What is the .1/LFE input and when do you use it?
The .1/LFE input, also an RCA connection, is the dedicated home theater input. LFE stands for Low Frequency Effects, which is the ".1" channel in a surround sound setup such as 5.1 or 7.1. Your receiver has a subwoofer output that sends all the deep bass information down this single cable. For most home theater setups, this is the input you will use. You run one RCA cable from your receiver's subwoofer output to this jack, and your receiver takes care of the rest.
Can the HT/1205 MKII connect wirelessly?
Yes, the HT/1205 MKII is compatible with the REL HT-Air MKII wireless system. This is an optional add-on that lets you send the subwoofer signal through the air instead of running a long cable across the room. It works by using a small transmitter near your receiver and a receiver at the sub. If your subwoofer needs to sit far from your electronics, or you simply want to avoid trailing a cable, this is a clean solution.
Controls: Dialing the Sub Into Your Room
What does the crossover control do?
The continuously variable crossover sets the point where the subwoofer starts taking over the bass duties from your main speakers. "Continuously variable" means you can adjust it smoothly to any point in its range rather than being stuck with a few fixed settings. If your main speakers are small, you set the crossover a little higher so the sub handles more of the low end. If your speakers already produce decent bass, you set it lower so the sub only fills in the very bottom. It is the tool that helps the sub and your speakers hand off to each other without a gap or overlap.
What does the gain control do?
The gain control adjusts how loud the subwoofer plays relative to the rest of your system. Turn it up and the bass becomes more prominent; turn it down and it steps back into the mix. The goal is balance, so the bass supports the sound without overwhelming it. You typically set this once by ear or with your receiver's setup routine, then leave it alone.
What does the phase control do?
The phase control lines up the timing of the subwoofer's output with your main speakers so their sound waves work together rather than against each other. When phase is set correctly, the bass sounds tight and full. When it is off, bass can sound thin or vague because the sub and speakers are partly canceling each other out. You adjust it during setup, listening for the fullest, most solid bass, and then leave it set.
Build Quality and Finish
Why does REL Acoustics build quality matter?
REL Acoustics has a long reputation for carefully engineered subwoofers, and that attention shows up in how the HT/1205 MKII performs and lasts. A well built sub controls its driver precisely, resists unwanted vibration in the cabinet, and holds up over years of use. For someone new to this hobby, buying into that kind of engineering means you spend less time worrying about the gear and more time enjoying it.
What finish does the HT/1205 MKII come in?
The HT/1205 MKII comes in a high gloss black finish. This is a smooth, reflective surface that looks clean and modern and blends easily with most media setups. Because a subwoofer often sits in plain view near your television, a tidy finish like this helps it look like a deliberate part of the room rather than an afterthought.
Who Is the HT/1205 MKII For?
Is this subwoofer right for you?
The HT/1205 MKII is a strong match for anyone building or upgrading a home theater who wants deep, confident bass from a proven brand. With its 12 inch driver, 500 watt RMS Class D amplifier, easy LFE connection, and helpful crossover, gain, and phase controls, it gives newcomers a subwoofer that is powerful yet approachable. If you love movies, games, or immersive sound and want a sub you can set up once and enjoy for years, this is a very comfortable place to start.