Subwoofers: Sizing, Wiring and Placement Guide

Bass is the part of a system people feel rather than hear, and it is also the part most often set up badly. This hub covers picking a driver size, choosing between sealed and ported enclosures, reading power and impedance figures honestly, and getting the placement right in a British living room or a car boot.

Choosing a driver size

Cone diameter sets how much air a sub can move, which broadly maps to how low and how loud it can go. Smaller drivers start and stop faster, which suits music with quick bass lines; larger drivers dig deeper and suit films and electronic music.

Size is not the only factor. A well-designed 10-inch sub in the right enclosure will outperform a badly boxed 12-inch every time, and enclosure volume is usually the limiting factor in cars and small rooms.

8-inch — tight and quick, fits under seats and in small rooms
10-inch — the best all-rounder for most cars and average lounges
12-inch — deeper output for home cinema and boot installs
15-inch — for large rooms and competition-style car builds only

Sealed versus ported enclosures

A sealed box traps air behind the cone, which acts as a spring. The result is tight, accurate bass with a gentle roll-off, and it forgives placement mistakes. Sealed boxes are smaller for a given driver, which matters in a car.

A ported box uses a tuned vent to reinforce output around a chosen frequency. It plays louder and lower for the same amplifier power, at the cost of a steeper roll-off below the tuning point and less control on fast passages. Get the port length wrong and the whole thing chuffs.

Reading power and impedance figures

Match your amplifier's RMS output to the sub's RMS handling, not its peak or 'max' figure. Peak numbers describe a brief burst and are quoted generously across the industry; RMS is the continuous figure that actually protects the driver.

Impedance is where most home installs go wrong. Voice coils are usually 2 or 4 ohms, and dual voice coil subs can be wired in series or parallel to present a different load. Wiring below your amplifier's minimum stable impedance is the fastest way to cook it, so plan the wiring before you buy.

Placement and crossover setup

In a room, bass builds up near boundaries. A corner gives you the most output and the least even response; a position a third of the way along a wall usually sounds smoother. The reliable trick is the subwoofer crawl: put the sub in your listening seat, play a bass-heavy track, then crawl around the floor and place the sub where the bass sounds best.

Set the crossover roughly 10Hz above the lowest frequency your main speakers handle cleanly, typically 80Hz for standard bookshelf speakers. Then check phase: flip the phase switch and keep whichever setting gives more bass at your seat.

Subwoofer size against typical application

Subwoofer size against typical application
Driver size	Best suited to	Enclosure that usually suits it
8-inch	Small rooms, under-seat car installs, music	Sealed
10-inch	Average lounge, most car boots, mixed use	Sealed or ported
12-inch	Home cinema, deep film bass, larger boots	Ported
15-inch	Large rooms and SPL-focused car builds	Ported

Buying checklist

Match amplifier RMS to subwoofer RMS, and ignore peak power claims
Confirm the final wiring impedance is stable for your amplifier
Choose sealed for accuracy, ported for depth and volume
Run the subwoofer crawl before you fix the position
Set the crossover near 80Hz, then check the phase switch both ways

Frequently asked questions

What size subwoofer do I need?

For most UK living rooms and most cars, a 10-inch driver is the sweet spot. Go to 12-inch if film bass is your priority and you have the space, and stay at 8-inch if you mainly listen to music or have a small room.

Sealed or ported — which sounds better?

Sealed boxes give tighter, more accurate bass and suit music. Ported boxes go louder and deeper for the same power and suit films and car audio. Neither is objectively better; they solve different problems.

What does RMS power actually mean?

RMS is the continuous power a driver or amplifier can handle without damage. Peak or max figures describe momentary bursts and vary wildly between brands, so always compare RMS to RMS.

Where should I put a home subwoofer?

Start about a third of the way along a wall rather than jammed in a corner, then run the subwoofer crawl to find the smoothest position. Corners give the most output but the most uneven response.

Can I wire two subwoofers to one amplifier?

Yes, provided the combined impedance stays at or above your amplifier's minimum stable load. Work out the series or parallel wiring on paper before you buy the second sub.

Why does my subwoofer sound boomy?

Usually placement or crossover overlap. A corner position, a crossover set too high, or the phase switch in the wrong position all cause a one-note boom rather than defined bass.