Just buoght a KLH sub that has the worst instruction manual that I have ever seen. It shows you how to hook it up but gives you no insrtuctions on how to use the settings. It has a knob for gain with settings that go from min to max and a knob for freq that ranges from 40hz to 180hz and a switch that says phase rev and nornal. Are there correct settings for these and what are the uses of each, so far I have just used my ears to judge the sound but I dont want the do any damage to it by not having it set in the correct way.
Usually you set the gain to about half to start and go from there to see if it needs to be boosted a bit or backed off to sound natural. The crossover (freq knob) sets your lowpass crossover frequency and this is to help you blend it with the rest of your speakers. You need to know the frequency range of the other speakers to set this properly. Try setting it as close to the low frequency cutoff of your main speakers as possible. You maybe able to turn this off and use the crossover in your receiver if it has one. As far as the phase switch goes, this allows you set it in phase just in case you wired the sub incorrectly. The cone (if you can see it) should be moving out, not inward.