SS filters are a good insurance policy when it transferred to the sub. If the low frequency (PTF signals below) occurs in the audio content, Sub "cancel" (cone becomes unstable), cardiac arrest, and passes to the state. In essence, we want to filter out as much as the audio signal through the power of the PTF as possible to avoid the destruction woofer.
For example:
We talk about SPL in dB or decibels. This is a unit of measure of how far the acoustic output of an audio system capable of playing. We know that the audio signals are electrical impulses from a source like a HU or amp. The amout of stress that can in turn be converted to level dB SPL. Hense SPL. The President (transducer) that converts electrical energy into sound waves. How many sounds we heard outside this room is usually expressed in dB SPL. (No power) Do you still lost?
Now transferred to most applications, we know there are a lot of energy down to today's "music. Some of the low that we can feel good. Very low frequencies (subsonics) are the signals in the presence, but we can not hear them. We feel the theater with movies like Volcano, Jurrasic Park, and how ... but they can not really hear. Caraudio subwoofer is used in these applications are huge and designed to reproduce bass below human hearing. Best, most of us can feel it ~ 25-30 Hz Bolow which is mostly less than our ears ... but we are able to hear it.
OK, back to business in the filters. Say you have a sub and amplifier. The amp is 300 RMS and the submarine is moderately effective. (89 dB SPL at 1 watt, 1 meter) The Caraudio subwoofer will play well indoors and the network of about 125 dB SPL in the low range of 40 to 150 Hz as the sub receives signals below ~ 40 Hz, the attenuation Natural # dB at a predictable rate. (Pending) The term used in audio-X dB / octave. In the case of a sealed box design, the slope is 0 dB at 40 Hz, -6 dB SPL in the loss of 20 Hz, -12 dB at 10 Hz (These are the octave and 10 Hz 40.20 .. ).
In planning the transfer, the Port tuning frequency (PTF), the amount of the lowest surface will be smooth and uniform. When the holes, you get a nice low-passive peak near the PTF. This peak is about 3 dB higher than the volume of housing supply with the same subspecies, and the input power. So now you have a 128 125 dB dB in the production of VS, which we mentioned earlier.
Near the PTF, Cone produces very little noise. The sound comes from the port. Cone does not move very close to the PTF as the pressure, the case was released in the door. This means that the movement of the cone, reducing the cooling coils. This is where a lot of diving to get fried. Not a lot of movement and a lot of power dissapated form of heat. It 'was the French sub roll.
Below the pressure against the FTC, yields cone movement, but there is also little in the box, he can not control the movement of the cone. (Play) Basically, it seems like there is no housing at all. (An "open skies") in the result. In the absence of control over the movement of the cone is spastic and would often blow up in the ditch or the offensive of the coil. Again, the result is a damaged sub.
When we use a SS filter, the filter will remove much of the sound energy that would normally be the woofer. The steeper the filter, the better. Less Watts (SPL) for the sub, below the FTC is how we protect woofers expensive. The most effective way to do this prior to amplification. It helps the amplifier because it does not lose large amounts of energy, trying to amplify signals in the PTF. In car audio, we do not receive a lot of music content below ~ 35-40 Hz If the PTF is to say 40 Hz Do we want to filter the content of the signal as much as possible as we approach TFP. This is where good filtering is needed.
Let's say that a submarine is to get 300 watts at 40 Hz signal is quite noisy things. Now insert a 40 Hz SSF, 12dB/octave, and the power output will decrease (~ 20 watts) flowing to the sub at 20 Hz is sure to heat in dissapate in this area. A 40 Hz SSF, 18dB/octave slope will reduce the power even more as. Here are obtained in about 4.5 watts at 20 Hz baseline of designing a good filter is to know that for every 3 dB of noise, we filter it falls watts input to the driver 50% .
Here is a table:
slope dB / octave ........................................ power to the Caraudio speaker
0dB reference ... (No filtering )..................... 300 watts @ 40 Hz
-3dB ................................................ ........ 150 watts @ 20 Hz
-6dB ................................................ ......... 75 watts @ 20 Hz
-9 ................................................ ......... 37.5 watts @ 20 Hz
-12dB ................................................ ....... 18.75 watts @ 20 Hz
-15dB ................................................ ....... 9.38 watts @ 20 Hz
-18dB ................................................ ....... 4.7 watts @ 20 Hz
See how it works? It logrithmic, not linear.
Hope this helps some of you as you watch the drawings ported box.
Swez
PS Most of the audio sales and installers are .... installers and retailers. This is the design and engineering kind of thing. Do not expect to know, unless they have studied in depth. I'm no expert in this area, but have been studied for some time. I hope that this presentation of a very complex issue, it is easy to learn and use
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