How to Choose a Subwoofer

October 25, 2013

By: Ken Humphreys - Speaker Engineer

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What’s A Subwoofer To Do?

A subwoofer’s calling in life is simply to bring deep, awe-inspiring bass to your movies and music. “All right, cool” you say, “Which one should I get?” Allow us to assist.

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Your Comparison Checklist

Please use this checklist as you shop for your new speakers

	Size—What is the right size subwoofer for your setup? Too big and it’s unnecessarily expensive and – well – too big. Too small and what’s the point? So, how big is just right?First, consider your listening room. Bigger rooms need bigger subwoofers to energize all that air space. Twice the room volume requires twice the energy from your subwoofer to maintain the same loudness.But far more important than room size is you! Do you like to crank up the bass or overall loudness? Do you listen to bass-heavy music or movies? You’re going to need a bigger subwoofer (or subwoofers.) On the other hand, those of you with tamer tastes are in luck. A smaller subwoofer will give you all the bass you need.If you want to hone-in on just the right size, we’ve put together a nifty Subwoofer Size Calculator.
	Power trips—We recommend only powered subwoofers – those with built-in amplifiers. The reason isn’t the power itself, it’s the many ways built-in amplifiers allow for extra control over the woofer.As for the actual power – rated in watts – it’s just one among many things determining how loud a subwoofer can play. It’s a little like horsepower to a car (actually, 750 watts is one horsepower): if it were the only thing making them go fast, you’d see Caterpillars lining up at Daytona.A pretty dependable rule is that most subwoofers, like cars, have a sensible amount of power for their design. Rather than focusing on power, we’re confident that the “size calculator” (see link above) will prove a more dependable way to know how much subwoofer you need.
	Be a control freak—Compare features and look for the ones you’ll want. Will you be using your subwoofer with a home theater receiver? If so, a “crossover bypass” switch on the subwoofer lets the receiver use its built-in crossover with less interference. If not, a “crossover” adjustment on your subwoofer helps it work well other speakers. A “phase” switch or knob is helpful in getting your subwoofer working properly with different room placements. And an “auto ON/OFF” feature automatically allows your subwoofer to relax when it’s not getting a work out.
	One Subwoofer or Two?—If you could see the way that bass really distributes itself throughout your room, you might be appalled – it’s way louder in corners and near walls and very uneven in between. Two subwoofers will smooth out a lot of this unevenness and allow you to get smaller subwoofer boxes. By the way, corner placement also has most of these advantages.
	Warranty—What is the manufacturers warranty? Is the subwoofer made by a company you trust will honor the warranty?
	In-home Audition and Return Policy— Your room is going to effect the bass. You won’t know how any subwoofer is going to sound like until it’s been fired-up. Make sure there’s a first rate return policy.
	Price—What does your wallet say? Are you looking for good value? Review all of your options and start crossing off the models that don’t have what you want. Then, cross of the models that cost too much because they do more than you need. Finally, compare the performances, features, sizes and the looks of those models still on your list.

Some of the questions below ask you to assign a number on a scale. Go ahead and estimate for in-between situations.

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Your Room:

____ Room volume. 0 point for 1000 cu ft; 1 point for 2000 cu ft; 2 points for 4000 cu ft; 3 points for 8000 cu ft; 4 points for 12,000 cu ft.

____ 0 points for a reflective room; 1 point for an absorptive room.

____ 0 points for subwoofer placement in a corner & on the floor (near three room boundaries); 1 point if near two room boundaries; 2 points if near only one (usually the floor); 4 points if outdoors.

____ 0 points of room is enclosed; 1 if open doors and hallways; 3 if room is very open (or if outdoors.)

____ Room score. Sum of above four scores.

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Your listening style:

____ How loud will the bass be at its loudest? 0 point if comfortable; 3 points if your wife tells you to turn it down; 6 points if you keep saying ”What did you say?”; 10 points if you know the cops on a first-name basis.

____ How demanding is whatever you listen to? 0 point for string quartets; 3 points for jazz; 6 points for rock & roll; 10 points for hip-hop.

____ Listening style score. Sum of the above two scores.

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Subwoofer style (Get from spec sheet of woofer under consideration):

____ How low is it rated to go (-3dB or cut-off frequency)? 0 points for 40 Hz; 1 point for 30 Hz; 2 points for <20 Hz

____ How big is it? (You can measure the outside in inches, multiply H x W x D, divide by 1728). 0 point for >4 cu ft; 1 point for 2 to 4 cu ft; 2 points for < 2 cu ft.

____ How many powered woofers are their in the enclosure? 0 point for two; 1 points for one.

____ How many subwoofers will you be using? 0 point for three; 1 point for two; 3 points for just one.

____ How would you rate the subwoofers overall quality? 0 point for great; 1 point for pretty good; 2 points for OK I guess.

____ Does it have a passive radiator or air vent? 0 points if yes; 1 point if no.

____ Subwoofer score: Sum of above five scores.

____ TOTAL SCORE: Add up the room, listening style and subwoofer scores

Total Score Suggested Size (woofer size, in inches)

Less than 22 points – 8” subwoofer(s) is all you probably need

22 to 24 points – 10” sub(s) should do

24 to 26 points – 12” sub(s) is recommended

26 to 28 points – 15” sub(s) is what you’ll probably need

Over 28 points – 18” or more for you!