Ported, Sealed or Transmission Line

Too many variables to sum up all of the different design attributes in even several very detailed posts. As such, you really do need to dig into the subject in order to have a better understanding of what is really going on. Take a look at this book about loudspeaker design if you're really interested. 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.

I will only say that Pepler's comments above are loaded with misconceptions based on the aforementioned design variables. This is not to single out Pepler as i'm sure that he's only trying to share what he knows. 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.

Turbulence or friction in a port is not ideal and that is not why they are doing that. They could have achieved similar results by redesigning the port, but that wouldn't look "special" or give them a gimmick to hype. Reading the aforementioned book will allow one to cut through the hype due to becoming an educated consumer. This pretty much allows one to dismiss inferior designs right off the bat without even having to listen to them. Looking at a speaker and picking out the visible design flaws becomes second nature once you understand how they work. 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. Sean
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Tobias: Not all low frequency designs try to eliminate the back wave. There are a few dipolar woofer designs that have achieved critical acclaim for their speed and high levels of in-room linearity. If you doubt this, ask Duke at Audiokinesis for a few references : )

I am using multiple sealed push-pull dipolar woofers in my main system. These are actively crossed with 1000 wpc driving them. Push-Pull lowers distortion and increases speed / self-damping of the drivers. Dipole's reduce in-room standing waves / smooth out in-room response. Sealing & stuffing the chamber between the drivers keeps the impedance down at resonance, producing a lower Q with the associated improvements in power transfer, transient response and "good tone".

As to "while a TL is superior to a sealed box"... those are Joe's words, not mine. Having said that, i will say that TL's are the best way to make use of the backwave from a woofer that i know of without exhibiting the multiple side effects that most vented systems suffer from. Vario-Vents aka Aperiodic's would be the second best vented design. A well designed port with flared inlets and outlets AND a good amount of internal cabinet stuffing would be third. Passive radiators find their way at the rear of the pack as they are the slowest of the bunch in terms of transient response. Having said that, a well designed PR system is probably capable of delivering more overall "bass weight" than any of the designs mentioned here. This has to do with the ability to tune the mass of the drone cone quite low in frequency AND that added mass adding more duration to each note due to overhang / slow transient response. As such, BIG woofers driving multiple BIG passive radiators are the way to go if you want "earthquake bass" in your house for HT use. Just don't expect it to be "tuneful" or "nimble" for use with music.

By the way, not all TL's are "vented". You can terminate a TL in a closed box and cram the end of the tunnel full of damping material to absorb the energy at the end of the line. Like i said, there are a LOT of variations to what is considered a "Transmission Line" and they all have their trade-offs / high-points. Sean
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