SPEAKER ENCLOSURE DESIGN PORTED TRANSMISSION LINE DRIVER
When Vilchur designed the acoustic suspension speaker he modified the driver spider to provide less spring restoring force on cone excursion because he knew the air in his sealed box would provide some restoring force. Tobias writes: Sealed box designs need more amplifier power, on the whole, because the cones have to work against the very stiff spring of the air trapped inside the box.Although stiffness is provided by the air in the sealed box, the spider on a driver designed for acoustic suspension is less stiff, and compensates. My supposedly humble opinion is that until you appreciate the tradeoffs involved in any audio design, you don't really appreciate the design. Sealed box designs need more amplifier power, on the whole, because the cones have to work against the very stiff spring of the air trapped inside the box. Sealed enclosures have a relatively low resonant 'Q' but the actual resonant frequency will be higher than that of an equal-sized, properly ported box. Every design is built around tradeoffs-you win on the roundabouts and you lose on the swings, as the British say.
That said, I am just as willing as anyone else to display my ignorance in public.Īny speaker design can result in a pleasing sound or not, depending on how it is implemented. There is much more to this question than you will conceivably get here, and you need a balanced view of your own. SeanĪlthough I am not sure Sean meant to suggest that the straw trick for reducing port turbulence or "chuffing" is pure snake oil, I quite agree with him that you need to do some reading. Only problem is, once you've attained this knowledge, you'll come to realize that "snake oil" is as much a part of the speaker industry as it is of the cable industry. Looking at a speaker and picking out the visible design flaws becomes second nature once you understand how they work. This pretty much allows one to dismiss inferior designs right off the bat without even having to listen to them.
Reading the aforementioned book will allow one to cut through the hype due to becoming an educated consumer. They could have achieved similar results by redesigning the port, but that wouldn't look "special" or give them a gimmick to hype. Turbulence or friction in a port is not ideal and that is not why they are doing that. Problem is that it is the same rhetoric that has been preached to audiophiles and it is basically wrong and / or a phenomenally small portion of what is a very big picture. This is not to single out Pepler as i'm sure that he's only trying to share what he knows. I will only say that Pepler's comments above are loaded with misconceptions based on the aforementioned design variables. Not only is this the most thorough and "relatively easy to understand" book on the subject that i know of, this is the best price that i've found. Take a look at this book about loudspeaker design if you're really interested. As such, you really do need to dig into the subject in order to have a better understanding of what is really going on. Too many variables to sum up all of the different design attributes in even several very detailed posts.
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