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<blockquote data-quote="Simon Coffin" data-source="post: 132733" data-attributes="member: 388">Re: No compromises front loaded double 18” cabHey Ivan,Interesting that you had better results with a triangular port.&nbsp; A stiffer cabinet would certainly help, but you may have unwittingly stumbled onto something with the port design.&nbsp; I wonder if the effective port length, which includes a certain amount of air at the mouth that extends beyond the port, changes with output level.&nbsp; At higher levels more air volume is involved and shifts the port tuning up or down.In the case of your triangular port, the boundary affect would have been more pronounced and would have narrowed the ports effective diameter.&nbsp; Yet, the greater air volume involved at the mouth may have compensated giving you a more stable port resonant freq.One thing that doesn&#039;t quite add up though is that a Helmholz resonator doesn&#039;t just use a given volume of air, its shape plays a role as well.&nbsp; The same volume of air in a long skinny enclosure resonates differently than in a short squat one.&nbsp; So if the effective shape of your triangular port is changing, shouldn&#039;t the resonant freq also change?Now that I&#039;ve written all this, I&#039;m not sure I understand the theory any better or not?!?CiaoSimonSimon</blockquote>

[QUOTE="Simon Coffin, post: 132733, member: 388"] Re: No compromises front loaded double 18” cab Hey Ivan, Interesting that you had better results with a triangular port. A stiffer cabinet would certainly help, but you may have unwittingly stumbled onto something with the port design. I wonder if the effective port length, which includes a certain amount of air at the mouth that extends beyond the port, changes with output level. At higher levels more air volume is involved and shifts the port tuning up or down. In the case of your triangular port, the boundary affect would have been more pronounced and would have narrowed the ports effective diameter. Yet, the greater air volume involved at the mouth may have compensated giving you a more stable port resonant freq. One thing that doesn't quite add up though is that a Helmholz resonator doesn't just use a given volume of air, its shape plays a role as well. The same volume of air in a long skinny enclosure resonates differently than in a short squat one. So if the effective shape of your triangular port is changing, shouldn't the resonant freq also change? Now that I've written all this, I'm not sure I understand the theory any better or not?!? Ciao Simon Simon [/QUOTE]

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