Helpful Tips

Audio Crossover Settings

by Rob Kole

Subwoofers add the bottom bass and punch to your music and movies. Setting one up correctly is both an art and a science. There are lots of articles about the proper placement of subwoofers in a room. This month's article is about setting your crossover split point. If you have ever dug into your receiver or subwoofer settings, you have come across "Crossover Frequency". This is the low end split point where your main speakers stop producing the bass notes and the subwoofer takes over. First, some basic knowledge of terms and hearing. A human can hear any frequency from 20 Hertz (the lowest rumble you can imagine) up to 20,000 Hertz (the highest shimmer of cymblas in an orchestra). Hertz= cycles per second. If you tap on something 60 times in a second, you will make a tone at that frequency. If you spin that hollow kids toy snake real fast, you will create a high frequencythat goes higher the faster you spin it. "Hz" is the abbreviation for Hertz, named after the physicist that charted the graph of human hearing.

When calibrating your receiver, it asks you if your speakers are LARGE or SMALL. This tells the receiver whether your speakers can handle deeper bass (large) or less bass (small). With good tower speakers, the crossover point can be moved downward to 80 Hz, allowing the thud of a kick drum (which occurs right at 100Hz) to come out of your main speakers, rather than the subwoofer. The subwoofer will then handle all of the low rumble below 80 Hz.When the receiver filters all of the bass frequencies out of your main speakers, it takes a big load off their back, asking them to only handle the mid and high notes. Bass is a power hog- that's why subwoofers have their own power amplifier, separate from the receiver. once it's gone, your speakers will sound clearer. It's like dividing up the chores, asking the smaller children to pick up the small toys and the teenagers to do the heavy lifting. 

If you have small bookshelf speakers, the crossover is set at or near 120 Hz, so the small speakers don't distort, and more of the frequency spectrum (ie. everything below 120 Hz down till the sub can no longer handle it, around 40-50 Hz) will come from the subwoofer.

Here's where things get tricky. Many people mistakenly set one crossover setting (ie. 100Hz) in their receiver, and then do it again on their subwoofer. This puts one filter after another, and effectively makes a filter at 50Hz, and all that comes out of the subwoofer is muted whale noises between 40 and 50 Hz. So if you set the crossover in your receiver, let your receiver do the traffic control and set your subwoofer crossover setting to BYPASS. If there is not a bypass switch, turn the setting knob all the way as high as it will go. this will insure that the low-pass filter in the sub (named that because it lets the low notes pass while filtering out the highs) will not get in the way. 

Note that if your subwoofer is turned off, your main speakers will sound thin- the receiver doesn't know that the sub is off, unless you set it to SUBWOOFER=NONE. Then the entire audio spectrum (lows to highs) is run through your main speakers. This is the correct setting for any system that doesn't have a subwoofer. 

Other subwoofer settings: set the phase to positive and the volume to approximately 70% as a starting point. All of our new receivers use an advanced room tuning software to make several settings at once. They come with a microphone that gets plugged into the front of the recdeiver. The Denon models have Audissey, and the Anthem models employ ARC (for Anthem Room Correction), which lets you tune the room from several different locationsin the room. We will discuss how these affect the subwoofer performance in a future article.

As always, if you have any questions or comments, email me or feel free to talk to the guys in the showroom, who are experts on the ideal settings for each receiver and subwoofer combination.

Kole Digital sells subwoofers from Paradigm, Atlantic Technology, Velodyne, Definitive Technology, Episode, Niles, Artison and Russound.