I didn't quite understand, it must have been the "?" at the end.
I'm not making any speakers like that, but my question is: if we move the speaker it changes the harmonics, so if we move the port would it have the same effect as moving the speaker?
From what I know, the "stub" is a way of eliminating harmonics, where you move the speaker from the end of the line, this way you create an area that fills the hole made by the harmonic, I think it is the 3rd harmonic that is eliminated (filled in).
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The Zd and Vd affect the harmonic structure of the eigenmodes in the box. The distance from the driver (or the vent) to the closest end, sometimes called a stub, createsa shorter wavelength to add to the major line harmonics. MJK first documeted it when he noted an anomoly in his model vrs test build was cause by the 6” (or so?) driver offset. Now this is commonly used to (mostly) chancel the lowest unwanted line harmonic so that it takes less damping to kill the rest of the unwanted and leaving more of the desired fundemental to reinforce the low end… ie more gain.
dave
dave
I get confused as to what the difference is between creating an offset stub up stream of the driver entry position (1/3 to kill the ‘3 x 1/4 wavelength resonance) and, instead, doing similar at the other end of the TL. The latter kind of makes a mess(in horn response) while the upstream offset is super easy and obvious (to me)?
plus, if you add a passive radiator you shift all of that by creating a mass loaded port affect? So 1/3 from the closed end isn’t the location of that resonances velocity max? Same thing happens if I shove the port exit in a corner or try to use an offset driver TL in the back if a car and then measure the alignment of that stub geometry. It shifts farther downstream with the end correction /loading at the end I guess?
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