Please 'Boom' Responsibly As most of you have noticed, the noise ordinances have become much tougher lately. Most of this is due to idiots, yes IDIOTS, who drive through residential areas with their windows down while their system is playing at full power. To make things worse, the music they listen to has all sorts of foul language that's not suitable for small children, (who may be playing outside). There are even a few people, who are even beyond idiot status, that play their systems at full power through residential areas after 10:00 PM (when many people go to bed). I don't believe that this type of behavior is good for the industry. If the fines get too stiff, people will stop buying large systems. If this happens, more people will get out of car audio (who wants a mediocre system). People get interested in things because they're exciting. A deck and four 6.5" speakers are not going to interest many of the younger car audio enthusiasts. If car audio enthusiasts keep annoying more and more people, the fines will keep getting tougher. All of this will only reduce interest in the equipment that fuels the industry. If you want to listen to your system at full volume, get out on the highway where there's little chance of bothering anyone. When you get to a red light, turn it down. If the only thing attractive about you is your 'system', you have some work to do. Bottom line... Think about what you're doing. Think about other people. It's not the end of the world if you have to turn the volume down for a little while.

Total Harmonic Distortion:
When an amplifier is driven with a signal, the output of the amplifier is an amplified version of the input signal PLUS any distortion created by the amplifier. All amplifiers and signal processors add distortion to the signal. The levels of harmonic distortion in a high quality amplifiers are sooooo far below audibility that they are basically of no concern. When someone tells you that one amplifier is definitely going to sound better because its THD is rated at .002% vs an amp with .05%, you can be pretty sure that he doesn't know what he's talking about. Many people believe that THD below 1% is not audible and I believe they're probably correct. The fact is, especially in an automobile, the amplifier is the least of your worries. Speakers used for mids and highs commonly produce between 1% an 5% THD and for subwoofers the numbers can easily reach 10%. This doesn't even take into account all of the resonances of all of the plastic and metal panels in the vehicle.
This next link is a large file (.5 megs) and will take a few minutes to download. Please be patient.
WARNING:Turn your sound card's volume to its lowest position before clicking on the link below.

This tone starts off 'clean'. At a point 5 seconds from the start, a 1% 2khz signal is mixed with it. At start +10 seconds, the 2khz level increases to 5% for a 5% total harmonic distortion. To hear the transition between 0 and 1% you may need to use headphones. You may have trouble hearing it through the computer's speakers. When the harmonics reach 5%, they are clearly audible. If the tone was music, you would have trouble hearing 5% THD. The 1 % is only barely audible and it's mixed with a continuous, steady tone. With music, it would be inaudible. This little exercise is just to show you how little 1% THD is and to help you realize that .000... % THD is useless as an indicator of sound quality.

You should remember:
1.An amplifier with the lowest levels of total harmonic distortion is not necessarily going to sound the best.

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