One look at the back of a subwoofer amplifier and your first thought might very well be "Yikes! What did I sign up for?" But relax - while each knob, gizmo and switch does have its own job, it's easy to understand what they do once you hear an expert explain it to you. Listen as Andrew Welker, Axiom Design Engineer, explains the Axiom subwoofer amplifier settings.

Subwoofer amplifier

Andrew Welker: I'm going to talk a little bit about the controls and the functions that are available on the backs of our subwoofers. These days, most of the actual set up and adjustments that you're going to be doing can be done within the menus of your home theater receiver or processor. But there are some cases, however, where you'll be using a conventional stereo amplifier to drive the subwoofers, so there are some adjustments that you need to set.

The first adjustment - and the most obvious - is the Volume Level. It's where you set how loud the subwoofer is going to sound for a given input signal. We recommend that if you're using a home theater receiver or processor, to set the volume as a starting point at the midway point. From there you can make the more fine adjustments using the set up menu in your receiver.

There's also the control on the back of the subwoofers that allows you to set the Crossover Frequency. In some cases it's just a two-position switch that allows you to set 80 or 150 Hertz; and in other cases it's going to have multiple settings from 40 Hz all the way up to 150 Hz. Again if you're using a home theater processor, you're going to set the crossover in the highest frequency setting which is 150 Hz and then you're actually going to set the crossover point inside the processor or receiver.

home theater

If you're using a stereo amplifier and you don't have bass management available to you, you're going to now set the crossover point to whatever makes sense with the speakers that you're using. Typically for a bookshelf speaker, an 80 Hz setting works well, and if you have the option and you're using larger tower speakers, something like the 40 or 60 Hz setting may work better. But it's something that you have to try and see which blends the best.

There's another setting called Phase which is in degrees. There's a 0° setting and a 180° setting. This is a setting that confuses people because if you just flip the switch with music playing, you're not going to hear much of a change at all immediately. This switch really defines how the subwoofer is going to interact with your main front speakers. To set it up is fairly simple: you want to play some music that has some good bass and mid-bass content in it, and then listen to the music playing with the switch in one position, and then switch it to the other position and listen again.

What you're listening for is there is going to be a setting that gives you fuller and slightly louder bass. That's usually the correct setting for your room.

Finally we have an input on our subwoofers that's labelled Trigger. There's an In and an Out available. The trigger simply allows you to turn the subwoofer amplifier on and off remotely from your home theater receiver or processor, so that when you turn the power on and off with your system remote control to the receiver, you'll actually be switching the amplifier in the subwoofer on and off.

This is a 12-volt trigger which is fairly standard in the industry. It simply uses an eighth-inch phono plug. So you're going to bring that signal from your receiver or processor and plug it in on the subwoofer amplifier. Now when you turn the electronics in the rest of your system on and off, it's going to switch the subwoofer amplifier on and off.

You'll know that's happening because normally the light on the back of the subwoofer will be green. If it's in the standby mode because you've turned off the power from the receiver it's going to turn red so that you know it's in the off position.