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<blockquote data-quote="Moble Enclosurs" data-source="post: 7616845" data-attributes="member: 634917">Basically, the port cross-sectional area deals with cutoff frequencies as well as length. Though in a dual 4&quot; aero setup, the cutoff is extremely high, you are allowing a lower range of frequencies to be more efficient in that area. By using only one, you are allowing less low end efficiency due to the area being smaller. There are two major formulas for this, but they are only for figuring cutoff, not controlling it. By using two, you decrease the cutoff, allowing more potential in the lower region due to the fact that any given response band is limited to a certain range. So, you want them as large as possible to increase efficiency closer to the sub frequency range of music.In horn design, this is common to understand the effects of low frequency response efficiency and how the cross-sectional area couples it to the environment. Any other design can benefit from this concept.The flaw of this that many know of, is to keep tuning low, the length is commonly increased to account for efficiency on the port end when in phase with the rest of the system. So, it has been known that a quarter or an 8th of the cutoff cross-sectional area can be utilized effectively to keep efficiency higher than a single conventional port alone. The also, well known effect of this is increased resonance nodes which usually creates a peaky response.If that does not make sense, I&#039;ll explain more, and even give the formulas if necessary.</blockquote>

[QUOTE="Moble Enclosurs, post: 7616845, member: 634917"] Basically, the port cross-sectional area deals with cutoff frequencies as well as length. Though in a dual 4" aero setup, the cutoff is extremely high, you are allowing a lower range of frequencies to be more efficient in that area. By using only one, you are allowing less low end efficiency due to the area being smaller. There are two major formulas for this, but they are only for figuring cutoff, not controlling it. By using two, you decrease the cutoff, allowing more potential in the lower region due to the fact that any given response band is limited to a certain range. So, you want them as large as possible to increase efficiency closer to the sub frequency range of music. In horn design, this is common to understand the effects of low frequency response efficiency and how the cross-sectional area couples it to the environment. Any other design can benefit from this concept. The flaw of this that many know of, is to keep tuning low, the length is commonly increased to account for efficiency on the port end when in phase with the rest of the system. So, it has been known that a quarter or an 8th of the cutoff cross-sectional area can be utilized effectively to keep efficiency higher than a single conventional port alone. The also, well known effect of this is increased resonance nodes which usually creates a peaky response. If that does not make sense, I'll explain more, and even give the formulas if necessary. [/QUOTE]

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