iMac Speaker Damage!??

[HalSamuel]

Hi, i was messing around on Logic 8 today, and i was on a tool that could adjust frequency. I had a sound playing, and i was boosting certain frequencies of the sound, and i boosted the sound to a very high frequency, then the speakers sort of spluttered and when silent. I tried adjusting the volume down, but the usual "blip" noise you get with the volume didn't sound. I stopped the track on logic, and tried again, and the blip sound was back again. I opened iTunes, and listened to some music, and, i could be completetly making this up, but i thought the high frequencies on the tracks sounded quite harsh. Is it possible that i could have caused speaker damage? i didn't have my volume that high when it happend, and the frequency can''t have been higher than 20khz. Any advice would be great