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settings my gains?? deck settings?
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<blockquote data-quote="Moble Enclosurs" data-source="post: 7553705" data-attributes="member: 634917"><p>Yes, it can get pretty confusing if you are not used to it. But one step at a time will do wonders with mathematics. So, let me know what you do not understand and I will explain it to you one step at a time.</p><p></p><p>As far as the formula, it involves speaker parameters as well as box parameters to get it to work.</p><p></p><p>Here is the first basic part of it:</p><p></p><p>The formula is this Fc=(Vas/Vb)^1/2(Fs). So, let's break it apart.</p><p></p><p>What is Fc? That is the cutoff frequency that we are looking for. Vas= the acoustical compliance of the speaker, which is the point of volume where the subwoofer will match the acoustical pressure of the environment, normally involving impedance, at the point where Z(acoustic impedance) nominally=413.3Ohms at about 68degrees. This is what I use to calculate it from scratch. But without all of that, just remember that VAS is a volume-thats all you need to know about it right now.</p><p></p><p>^1/2 is the same thing as saying a sqrt, but for simplicity just use a calculator for the power of the variable Xy. To do a power on a calculator, type in the numerical value, then the ^1/2 is hitting the Xy button, then 0.5.</p><p></p><p>Fs=the drivers resonant free-air frequency, or 0 referenced impedance point where excrusion is maximum, and do not confuse this with a box's Fs, where conventionally, it is impedance minimum, not flat referenced at 0 on a graph. So, the Fs of the driver is in the specs you get from them.</p><p></p><p>Vb=the volume of the enclosure, in any cubical form, cFt, cc, Cin, m^3, etc.</p><p></p><p>THE KEY IS TO MATCH THE VAS WITH THE VB in reference, so if VAS is in cubic ft, VB should be in cubic ft as well, and the solution will be in cubic ft.</p><p></p><p>Calculate: Everything in parenthesis first. PMDAS is the mathematical key for any formula as an orer of preference. This means: parenthesis, multiply, divide, add, subtract. This is the order of any formula. So, whatever is in parenthesis first, do that. If all is in (), then multiply, etc.</p><p></p><p>So, in this formula, first is VAS/VB. Say VAS is 68 liters(2.4 cubic ft). And VB is 2.5 cubic ft. So, 2.4/2.5=0.96. Now, this needs to be powered. The power of a solution takes presidence over PMDAS order. The solution that has a power HAS TO BE powered first, and here the solution is VAS/VB because it is in parenthesis and the power follows the parentheses.</p><p></p><p>SO, the ^1/2 power or sqrt of 0.96=0.9798. This is then multiplied by the next order, which is in parentheses all on its own. This means, if it is on its own, it is already a solution within the PMDAS rule, so everything outside of it can be done first. Then 0.9798(Fs) is the same thing as multiplying them together. So, 0.9798*Fs, if Fs is for example 41Hz, then the final solution is =40.17Hz for the cutoff point of that design volume with that speaker. This is based on a dB scale and mechanical scale of excursion control, so port calculations are not figured in. Tuning calculations are done separately, and that is where the port is figured in.</p><p></p><p>Keep in mind that this is not shown on the response likely, but more so for setting the gains for excursion control. The port, again, will have its own cutoff point, which WILL show up on a design. This is for setting gains, not showing response graphs. If it has to do with response graphs, then it would be the -3dB point, which Im sure they might not be the same thing. ALSO, that this is for a smooth response using a Q of 0.707. And with the Q changed, this may change the solution. The ^1/2 is the key to the 0.707 Q factor. So, this is with optimum volumes. I am not sure if I mentioned that before. And this is also based a LOT on the drivers resonance free-air but works in the real world. Most of the time, the solution is pretty low, which is good for excursion control.</p></blockquote><p></p>
[QUOTE="Moble Enclosurs, post: 7553705, member: 634917"] Yes, it can get pretty confusing if you are not used to it. But one step at a time will do wonders with mathematics. So, let me know what you do not understand and I will explain it to you one step at a time. As far as the formula, it involves speaker parameters as well as box parameters to get it to work. Here is the first basic part of it: The formula is this Fc=(Vas/Vb)^1/2(Fs). So, let's break it apart. What is Fc? That is the cutoff frequency that we are looking for. Vas= the acoustical compliance of the speaker, which is the point of volume where the subwoofer will match the acoustical pressure of the environment, normally involving impedance, at the point where Z(acoustic impedance) nominally=413.3Ohms at about 68degrees. This is what I use to calculate it from scratch. But without all of that, just remember that VAS is a volume-thats all you need to know about it right now. ^1/2 is the same thing as saying a sqrt, but for simplicity just use a calculator for the power of the variable Xy. To do a power on a calculator, type in the numerical value, then the ^1/2 is hitting the Xy button, then 0.5. Fs=the drivers resonant free-air frequency, or 0 referenced impedance point where excrusion is maximum, and do not confuse this with a box's Fs, where conventionally, it is impedance minimum, not flat referenced at 0 on a graph. So, the Fs of the driver is in the specs you get from them. Vb=the volume of the enclosure, in any cubical form, cFt, cc, Cin, m^3, etc. THE KEY IS TO MATCH THE VAS WITH THE VB in reference, so if VAS is in cubic ft, VB should be in cubic ft as well, and the solution will be in cubic ft. Calculate: Everything in parenthesis first. PMDAS is the mathematical key for any formula as an orer of preference. This means: parenthesis, multiply, divide, add, subtract. This is the order of any formula. So, whatever is in parenthesis first, do that. If all is in (), then multiply, etc. So, in this formula, first is VAS/VB. Say VAS is 68 liters(2.4 cubic ft). And VB is 2.5 cubic ft. So, 2.4/2.5=0.96. Now, this needs to be powered. The power of a solution takes presidence over PMDAS order. The solution that has a power HAS TO BE powered first, and here the solution is VAS/VB because it is in parenthesis and the power follows the parentheses. SO, the ^1/2 power or sqrt of 0.96=0.9798. This is then multiplied by the next order, which is in parentheses all on its own. This means, if it is on its own, it is already a solution within the PMDAS rule, so everything outside of it can be done first. Then 0.9798(Fs) is the same thing as multiplying them together. So, 0.9798*Fs, if Fs is for example 41Hz, then the final solution is =40.17Hz for the cutoff point of that design volume with that speaker. This is based on a dB scale and mechanical scale of excursion control, so port calculations are not figured in. Tuning calculations are done separately, and that is where the port is figured in. Keep in mind that this is not shown on the response likely, but more so for setting the gains for excursion control. The port, again, will have its own cutoff point, which WILL show up on a design. This is for setting gains, not showing response graphs. If it has to do with response graphs, then it would be the -3dB point, which Im sure they might not be the same thing. ALSO, that this is for a smooth response using a Q of 0.707. And with the Q changed, this may change the solution. The ^1/2 is the key to the 0.707 Q factor. So, this is with optimum volumes. I am not sure if I mentioned that before. And this is also based a LOT on the drivers resonance free-air but works in the real world. Most of the time, the solution is pretty low, which is good for excursion control. [/QUOTE]
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