Multiple subwoofers: If one's good, two are even better

Subwoofers do bass, it's their thing. That's easy enough to understand, but even if you've picked out a great sub, there's no guarantee you'll wind up with great bass in your room.

Two subs are good, four are even better.

(Credit: Polk Audio)

Why's that you ask? Room acoustics are tricky to understand, and picking the right spot for the sub is key. I've covered this before in my Subwoofer Setup Guide blog, but this time I'd like to take a different approach--using two or more subs to smooth out bass-busting room anomalies.

"Standing waves" within the room can cause large frequency-response variations at the listening locations. That's why some of Paul McCartney's bass notes are clear as can be, some seem much lower in volume, and some are bloated. That happens because some of Paul's notes are reinforced by your room's dimensions, while some are diminished.

Further, the subwoofer's frequency response changes significantly from one listening location to another. When you're sitting near the center of the couch all the notes might be even, but move over two or three feet, and the bass gets lumpy. Stand up and walk around the room, and the bass can sound radically different from spot to spot.

Adding a second (identical) sub automatically reduces the first sub's workload, which effectively lowers the distortion for a given playback volume of bass. Predicting room acoustics for amateurs and pros is fraught with uncertainty, but generally speaking, placing the subs on the midpoints of opposite walls is a good starting strategy (as in my illustration above). Diagonally opposite room corners can also work well.

Four subs, located at the midpoint of each wall will produce even smoother bass response throughout the room.

And yes, two decent 10-inch subs, properly placed can deliver higher quality bass than one 12-inch sub. Two $600 subs can sound better than one $1200 sub.

[theonlybuster]

I'm a (semi) professional sound guy and I must say adding multiple subs is really tricky. We once installed some on a football field for a show and the set-up took hours, but it was basically because of tweaking and making sure there were no dead-spots randomly throughout the field. Of course you can't catch every single bad spot, but the more time you put into it the better it sounds. But nice job Steve, I'm reading your other articles and they're full of simple stuff, but it's the simple stuff many people overlook or just don't spend too much time working on.

[Vantage123]

First it was 5.1 sound then came 7.1, now 7.2 is out. I ask; why don't they just come out with 7.4 and be done with it?

[ender21]

This isn't 7.2 or 7.4. It's your normal sub channel, split into 2 for 2 subs, or split into 4 for 4 subs. It's still just 5.1 or 7.1 sound, though.

[bob.mcclenahan]

Good subs are expensive. If I get four, can I get cheaper ones?

[DaveOCP]

Multiple subs lessens the need for a ton of wattage, so you can go with more affordable subs and still achieve similar SPL. What you don't want though is to cheap out to the point where you start giving up quality. Smoothing out room modes with multiple subs is meaningless if the subs are one-note rattle boxes. Two subs with room correction EQ should be more than enough. Four subs is just overkill.

[Vantage123]

As all the posts here have said; it's a matter of proper placement and number of the subs that define the tonal character of the music being played back. Shaking the house does no good. There needs to be a method to adjust the sound, such as multiple mic's located at different locations within a room while the receiver goes through its calibration procedure. When that becomes available then the investment made in all speakers in the room can be fully realized. Is there such a method or system out there that can do this?

[snagglepussca]

there is a computer based program that will do exactly what you say and for the other speakers in your system. There is a store in Toronto called Audio Excellence that is selling it.

[ender21]

There's also room correction software such as Audyssey MultEQ that exists in many receivers and pre-pros nowadays. It's not multiple mics in the room, it's one calibrated mic in multiple locations (from 2 to 32 measuring points, depending on the hardware you purchased). It measures speaker response, including subs, in both the frequency and time domain and attempts to flatten out your frequency response.

It can't make a recording studio out of a tile room, but it *does* work very well.

[Down4Mine]

agree 100% with this article. the comparison between jimi hendrix and SRV, and the idea that they would also be suffering from harsh criticism had they survived to see their decline is an irrelevant one. Why? Because at the height of their popularity they were at least interesting to watch and listen to. Eric Clapton's music has always been on the bland side. How about a good example where Eric Clapton's mediocrity is plain to see. When George Harrison was inducted into the rock and roll hall of fame, prince played the part of clapton's solo during While My Guitar Gently Weeps. Needless to say, he simply outclassed clapton in every aspect. Sheer musical talent and showmanship.

[ALUXON2001]

prince showman yes, musical talent none what so ever

[bongees]

I thought about this but didn't think it was possible. How do you hook up a second sub? I would definitely like to experiment with this idea.

[jose_ams]

Every Sub must have its own amp, thas another extra cost.

[cardes]

Ahem *cancellation* ahem. Sorry, excuse me, were you talking about wasting more money? :D