Subwoofer setup 101

03/06/2015 Paul Helvin

I often get asked many questions regarding subwoofer placement, crossover setting, size, etc..

Although there are many articles on the internet shedding light on this topic, everyone seems to have their own take on how it is done. Well since we sell subwoofers and set them up here at Premiere, I would like to share my observations and knowledge that I have gleaned through my years in the hobby.

Subwoofers have 4 main sizes in general. An 8″ 10″ 12″ 15″ driver(s). They also have many configurations but the main two are “Sealed & Ported”

As a matter of physics, the larger the driver, the lower the frequency response. Also, the higher wattage in the built in amplifier, the higher the output of overall bass. (there are exceptions to the rule, put a 1,000w amp on an 8″driver and see what happens!). The opposite to this rule can also apply, put a 150w amp on a 12″ driver and you may be somewhat underwhelmed.

Amplifier technology has come a long way however, especially with class D (switching) power supplies, but in general I find the above observations to ring true.

In speaker box design, a ported sub can output more overall bass or SPL, but a sealed subwoofer can seem cleaner or tighter through its stated performance specifications.

In general you want to stay away from corners as this can make the Bass seem bloaty and less accurate.

As a rule of thumb, I use the LFE output on a sub if my processor has a “sub out” connection on the back. I then use the crossover in the processor to work out the Bass 3

When connecting a subwoofer to a 2 channel only analog preamp (no crossover) I use the stereo left and right connections into the back of the sub and use the subwoofers built-in crossover controls on the back panel.

In the “LFE”(low frequency effects) connection mentioned first, I set the subs crossover all the way up. This bypasses the subs crossover settings completely and avoids any bleed or crosstalk between the processors crossover and the subs internal one.

Some subwoofers are made with 2 or more drivers, some facing back to back or with a passive radiator canceling distortions . Designers are always looking for new ways to get better base performance in a relatively small space.mar2015-blog2

Some subwoofers face down, and some up. In general I find that a downward configuration is good for movies (wood and tile floors need not apply!), and front firing good for music. However I leave mine front firing at all times.

When setting a subs crossover, I will make the setting around 10Hz above what my front speakers are capable of at their lowest measured bass performance.

For instance if my front speakers go down to 30Hz, and I set them to small and 40Hz in my processor (10hz above speakers lowest capabilities puts less strain on speakers and amp), then I will set my subwoofer at 50hz so that the subwoofer blends with the fronts as the bass energy from the fronts falls off and the sub kicks in.mar2015-blog4

I set the volume so that the bass blends with the fronts so that you would not even know a subwoofer was in the room.

As always there are different schools of thought on this. Remember THX? They say set the sub a 80hz always.

One last note; I find a very large performance improvement in power conditioning as well as a quality sub cable. Like with any other component in the signal chain don’t skimp on this!

Visit us at Premiere to see the many options of subwoofers we carry in 2 channel and theater applications. And if you would like to share with us how you have your subwoofer connected let us know!