Quote:
Originally Posted by Bill Fitzmaurice 
It's actually closer to 100Hz. However, even with a brickwall low pass filter there will still be a lot of content above the crossover frequency. That's because subwoofers (all speakers, actually) create harmonics of the source signal, so while the signal into the sub may be 80Hz. there will be audible harmonics at 160 and 240Hz, if not even higher. Additionally, the louder the sub is played the higher the harmonic content, and the easier it is to localize. For these reasons you may need to take the crossover frequency even lower than 80Hz to eliminate localization.

It's actually closer to 100Hz. However, even with a brickwall low pass filter there will still be a lot of content above the crossover frequency. That's because subwoofers (all speakers, actually) create harmonics of the source signal, so while the signal into the sub may be 80Hz. there will be audible harmonics at 160 and 240Hz, if not even higher. Additionally, the louder the sub is played the higher the harmonic content, and the easier it is to localize. For these reasons you may need to take the crossover frequency even lower than 80Hz to eliminate localization.
I wish to add my grain of salt to that. While it's perfectly true that harmonics may be localized since they get generated above 80-100 Hz, they're not un-avoidable. If you have a signal and the sub reproduces it perfectly with no (or more realistically, negligible) distortion, then there's no audible harmonics that are generated. Unwanted harmonics appear because of distortion and become audible when a sub is pushed at (or close to) its limits. If it's not the case then there's no reason to fear localized harmonics.
(One way to understand harmonics: any signal can be decomposed as a sum of perfect tones. Each tone is a single frequency sine wave. If you take that perfect sine wave and squish it because of clipping or non-linear distortion due to the amp or driver being pushed too hard, then the resulting waveform can itself be decomposed as the original, fundamental perfect sine wave, plus harmonics -- overtones -- at multiples of the fundamental frequencies. Thus distorting the signal results in unwanted harmonics at higher frequencies).


























those older Energy's are awesome values. It's hard to keep perspective given the crazy blow-out pricing we've seen the past couple of years on RC's and now the new Veritas, but if you are diligent you can build an awesome setup for not a lot of cash by pursuing older stuff.