Mono Subwoofer Amplifiers: Why Subs Run Mono and How to Choose One

A mono subwoofer amplifier, or monoblock, is a single-channel amplifier built to drive subwoofers. Subs run mono because low bass is non-directional, so the left and right bass is summed into one channel and sent to a monoblock, which is more efficient than running a sub in stereo. This covers what a mono sub amp is, why subs are mono, and how to pick one for your system.

Monoblocks are the standard way to power a subwoofer stage. If you are still choosing the sub itself, see our truck subwoofer guide and the subwoofer collection. To shop mono amps directly, browse Class D amplifiers.

What is a mono subwoofer amplifier?

It is a single-channel amplifier, called a monoblock, that puts all of its power into one output to drive a subwoofer. Unlike a 2-channel or 4-channel amp that splits power across left and right, a monoblock is built to do one job: make a lot of clean low-frequency power into a low impedance. Nearly all of them are Class D for efficiency, and most are stable down to 1 ohm so they can run one or more subs wired to a low load.

Why are subwoofers run in mono?

Because low bass is non-directional. Below roughly 80 Hz your ears cannot locate where the sound is coming from, so there is nothing to gain from a separate left and right subwoofer signal. The left and right bass content is summed into a single mono channel and handed to a monoblock. That is simpler, and it lets one efficient amplifier put all its power into the sub instead of splitting it across two channels that would only reproduce the same non-directional bass.

This is also why "mono subwoofer" and "mono subwoofer amplifier" describe the same setup from two angles. The sub is run in mono, and the amp that runs it is the monoblock.

Mono amp or bridged 2-channel for a sub?

For a dedicated sub, a purpose-built monoblock usually wins. A 2-channel amp bridged into one output can drive a sub, and it is a fine way to reuse an amp you already own, but a monoblock is generally more efficient, is stable at a lower impedance (often 1 ohm where many bridged 2-channels stop at 4), and comes with the controls a sub needs: a low-pass filter, a subsonic filter, and bass boost. If you are buying for a sub, buy the monoblock. Monoblocks are Class D for the same efficiency reasons covered in our Class AB vs Class D breakdown.

This walks through wiring subwoofers to a monoblock the right way:

Best mono subwoofer amplifiers we carry

These are Class D monoblocks we stock, spanning a compact budget amp to a high-output SPL block. Power figures are published RMS at each impedance.

Image Dynamics SQ1200.1D: the house-brand value pick

The Image Dynamics SQ1200.1D makes 1200 watts RMS at 1 ohm, is 1-ohm stable, and includes the full set of subwoofer controls: 40-click bass boost, and adjustable subsonic and low-pass filters, plus a remote level control. At $504.99 it is the value pick for a single strong sub, and Image Dynamics is a brand we carry and stand behind.

Wavtech link1500.1plus: the compact all-rounder

The Wavtech link1500.1plus holds 1500 watts RMS from 2 ohms all the way to 1 ohm in a chassis just 1.65 inches tall, and instead of a simple bass boost it carries a bassFREQ parametric processor for tuning the low end. It is the pick when you want serious power in a slim amp with real tuning control, at $699.99.

US Acoustics Big Ben: the high-output pick

When you want real SPL, the US Acoustics Big Ben delivers 3500 watts RMS at 1 ohm, with variable bass boost to +12 dB, a Butterworth low-pass, a subsonic filter, and a wired bass remote. US Acoustics also scales up the line, from the Mike at 1500 watts ($329.99) to the Phil at 8000 watts ($1,249.99), if you need more than the Big Ben's $599.99 output.

Wavtech link1000.1mini: the compact budget pick

For a single sub in a tight space on a budget, the Wavtech link1000.1mini makes 1000 watts RMS at 2 ohms from a 12.2-inch chassis at $399.99. Note it is rated to a 2-ohm minimum rather than 1 ohm, so wire your sub to present 2 ohms to this amp.

How to match a mono amp to your sub

Match three things: power, impedance, and gain. Read the sub's RMS rating, then read the amp's RMS output at 4, 2, and 1 ohm and wire the sub to the load where the amp makes about that power. Mind the ohm math: two 2-ohm voice coils in parallel present 1 ohm, two 4-ohm coils in parallel present 2 ohms, and two 2-ohm coils in series present 4 ohms. Never wire below the amp's minimum stable impedance.

Then set the gain by target voltage, not by ear, so the amp reaches its rated power without clipping. Our gain guide walks the procedure, and the gain calculator gives you the target voltage for your amp and load.

This tutorial covers setting the gain on a mono subwoofer amplifier:

Frequently Asked Questions

Where to go next

Pick the sub first, then the monoblock to match it. Browse mono Class D amplifiers and the subwoofer collection, and if it is a truck, the truck subwoofer guide covers the behind-seat side. When it is wired, set it with the gain guide.

Not sure which monoblock matches your sub and your wiring, or what impedance to run? Contact us. We match amps to subs and set them by measurement on every system that leaves the shop.