WTF logartihms (setting crossover frequencies)

[emilimo701 10+ year member]

Most amplifiers that i've seen are not very well labeled, especially when it comes to their knobs and dials.

So to get as close as possible to the actual crossover frequency, I've turned to math.

The frequency of a wave grows exponentially to its perceived pitch. So let's say a signal can be filtered anywhere from frequency X to frequency Y. This (I THINK) should be the equation for finding the percentage (between points X and Y) to turn the dial to cross over at frequency Z:

(log Z - log X) / (log Y - log X)

Am I wrong?

Because if you check out the 80Hz mark on Infinity/JBL amps... it is set about 60-70% between 32Hz and 320Hz.

But if you plug in to my equation, 80Hz should be somewhere around 40%.

Also, Alpine/RF amps are marked at about 6 locations which is nice but it doesn't seem to follow a logarithmic scale whatsoever... the marks are equally spaced but the frequencies go up and down in proportionality... and exponential/logarithmic curves should, even if imperfect, at LEAST be proportional. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

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[KyleBechtold 5,000+ posts]

its based on the amp.. different amps different slopes..

 

[T3mpest 10+ year member]

just set the crossover by ear. Their is nothing magical about 80hz I promise. Mixing slopes and under/over lapping crossovers is fine. What matters is the acoustic summation at the crossover frequencies and hitting your intended curve and protecting drivers.. In short, if it sounds good, go with it.