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<blockquote data-quote="Moble Enclosurs" data-source="post: 7553436" data-attributes="member: 634917">Thats where design comes into play. With the design, you can figure for cutoff by this: Fc=(Vas/Vb)^1/2(Fs). So, if you driver&#039;s VAS is 126.8 liters(4.48cFt), and Vb is 4 cubic ft, and Fs is 27.8Hz, Then the ideal cutoff is 29.42Hz(-3dB). Vas has to match Vb, so if you use cubic ft in acoustical compliance, the box volume has to be in cubic ft as well. With 4th orders, this may seem to be lower than normal due to the peak, but it is reference.I am not sure how well &quot;programs&quot; may agree with this. I do not use them. Maybe winisd or hornresp may say different, idk.Now, I believe with the 4th orders, since this may be different, that the formula for them may be different, because of the sealed portion of the design having an effect on it. Ill have to check my worksheet for the formula on that. But after that, the actual tuning may be calculated as: Fb=0.42(Fs)/Qts^0.9, which would equal 54.65Hz or thereabouts.Ironically, I have seen this fc formula used in a &quot;cookbook&quot; worksheet somewhere. Google it, might come up with more info on it, idk.</blockquote>

[QUOTE="Moble Enclosurs, post: 7553436, member: 634917"] Thats where design comes into play. With the design, you can figure for cutoff by this: Fc=(Vas/Vb)^1/2(Fs). So, if you driver's VAS is 126.8 liters(4.48cFt), and Vb is 4 cubic ft, and Fs is 27.8Hz, Then the ideal cutoff is 29.42Hz(-3dB). Vas has to match Vb, so if you use cubic ft in acoustical compliance, the box volume has to be in cubic ft as well. With 4th orders, this may seem to be lower than normal due to the peak, but it is reference. I am not sure how well "programs" may agree with this. I do not use them. Maybe winisd or hornresp may say different, idk. Now, I believe with the 4th orders, since this may be different, that the formula for them may be different, because of the sealed portion of the design having an effect on it. Ill have to check my worksheet for the formula on that. But after that, the actual tuning may be calculated as: Fb=0.42(Fs)/Qts^0.9, which would equal 54.65Hz or thereabouts. Ironically, I have seen this fc formula used in a "cookbook" worksheet somewhere. Google it, might come up with more info on it, idk. [/QUOTE]

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