SPL competitions?

What kind of test tone do SPL comps use to measure how loud your stereo is? Is it just at a certain frequency or do they play a sweep or what. I have only been to one and it was at the end after they had measured everyone's systems:(

How would you know what track would play the loudest in your system ,and do they let you use something like a radioshack spl meter to find this out before the competition starts or do you need to find this out before you come to it?

Here is the basic skinny for you, it can be accomplished two ways.

(1) find the loudest bass note in the vehicle. For this you need a meter calibrated to read decibels. Run the sinewave sweep and watch the numbers, at some point (usually between 80-50hz) you will see the loudest resonant frequency of the system. This is the frequency that the system will play loudest at. It will vary widely between different types of boxes.

(2) The second way to do this is to find the loudest resonant frequency of the vehicle and then tune the speaker system to that frequency. This is a lot more indepth but the basic's here are a truckload of sound deadening, a sine wave sweep to find the loudest resonant frequency of the vehicle (requires some experimentation), building the box calibrated to that particular frequency and finally playing a note at that particular frequency. This is usually done with a ported enclosure, sometimes a bandpass.

I don't specialize in SPL, but this should put you on the right path. Maybe someone here can offer a little more input.

What you need to find the freq. that it plays good at? i have a sound genterator, that i've yet to play in the car- made my own sweeps and  tracks.