I'd appreciate comments on the following section from a forthcoming book I'm writing on HT. This part is about how to set the various switches and dials on the back of a sub. Other parts of the setup, such as bass management and receiver setup (e.g., "small" vs. "large" speakers) are covered elsewhere in the book--the section below is only about what's on the back on the sub. Also, the only case this applies to is a powered sub connected to a line-level sub output on the receiver, and with nothing connected to the sub's outputs. Setting Up the Subwoofer Unlike the other speakers, a powered subwoofer has a bunch of dials and switches on its back that have to be set up just right, or else it won’t work well with the other speakers as it’s supposed to. Each model is a little different, but the following instructions are typical: •A switch turns the subwoofer’s low-pass crossover circuit on or off. Turn it off (or “out,” as it may be marked), because you want the crossover to be done in the receiver. •A dial sets the low-pass crossover frequency. This sets an upper limit on what frequencies the subwoofer will handle. However, this circuit is disabled (previous paragraph), so it doesn’t matter what you set the dial to. Set it to its maximum just to be safe. •A switch or dial sets the high-pass crossover frequency, which has to do with output from the subwoofer. It doesn’t matter what you set this to, since you will not be connecting anything to the subwoofer’s outputs. Set it to the maximum just to be safe. •A volume control. When you adjust the sound levels for the whole system, you’ll be setting the subwoofer’s volume at the receiver, not with this control. Set it to something and then make sure it isn’t accidentally bumped to another setting by mistake. I suggest you set the subwoofer’s volume to about the three-quarter point and then move it from there only if you later find that the receiver’s sub-woofer volume setting is unreasonably high or low. •A phase switch. You set this for maximum bass. There’s an easy-to-use test on the Avia disc that helps you set this switch correctly.