Distortion essentially only occurs when the Xmax is being exceded (which can be done withou damage). If you have a ported box, and you play it below the Fs, then you unload the port and air is allowed to flow through it, and the cabinet loses its compression/rarefication properties, it also loses the ability to control the speaker, and it will begin to move much further, when it hits the end of its travel it stops, thus creating the distortion. DO NOT however think that this means speakers wont die when you do this, but it won't be immediate, but... the voice coil gets EXTREMELY hot when the speaker stops at an extended or retracted point, and it will burn up the coil after not too long.
In a sealed box, distortion occurs if you play it too loud. Also you asked about frequecy drop. As the frequency decreases, the wavelength increases thus calling upon the speaker to move farther. Hence why tweets are hard to destroy. 5k doesn't require much distance from the diaphragm, only speed, which is why they are small. Now... playing below the F3 point. no way around it, if you don't filter it, the speaker WILL be playing below the F3 point, BUT, that is meaningless, because, for anyone who wasn't sure... F3 came from at what Frequency (F) the sound would be 3dB less (3). Hence F3. 3dB is a detectible gain or loss to the human ear. So what makes the F3 point significant is not that it plays no lower, it just becomes so much quieter than the rest of the sound you can't hear it. After the F3 most subs roll off at 12dB per octave. By multiplying the power by 10, you double the output volume (10dB gain) In THEORY. THEORY.
THEORY...
If you could build an autosetting amp that would compensate logrythmically for the F3, and double the power every octave below the F3 your bass extension would be limitless. But, we're back to excursion. no sub could take it. But if a guy had a magic sub that had xmax infinite, and the magic amp that self adjusted below the F3, you could boom as low as you want. But since hearing stops at 20Hz, you wouldn't care.
So if you had a huge sub... Kicker Solo X
18 inch, 10,000 watt...
if you were playing at 40Hz, and say 20Hz was F3.
At 40 Hz, if you were pumping in 100watts, at 20Hz you would need around 1,200 watts (12dB), at 10Hz 14,400 watts. WAIT! your thousand dollar Solo X just burnt to a crisp, and the surround is laying in the floor! Oops!
Even if your sub could take 100,000 watts, play it at 5 Hz, you need 172,800 watts, Crap, I just blew up a sub so powerful it doesn't exist, just because i tried to go 3 octaved below F3 and still hear it.
Continue the example 2.5Hz 2,073,600 watts
1.25Hz 24,883,200watts
.625Hz 298,598,400watts
.3125Hz 3,583,180,800watts
THREE BILLION WATTS?! Wow, that kind of power doen't exist in any amp I've seen...
hope I helped answer your question.
|
|