Ported, Sealed or Transmission Line

Infinite Baffle sounds like a cable manufacturer's technical White Paper. :o)

It's also what you get when you set a speaker in a wall, or in a floor like some subwoofers of the fifties. ( Think of the low end from an 18-inch EV hung just under your feet! )

The term means that the driver's back wave is " baffled " as it tries to come round and cancel out the front wave, which is in opposite phase. It's a British term and in England the baffle of a speaker is its front panel. When a speaker is mounted in a wall, the back wave has, for practical purposes, an infinite distance to travel before it can cancel anything out.

Of course all dynamic loudspeaker designs try to either eliminate or control the cancellation effect, which is most serious in the bass. That's why we put drivers in boxes in the first place.

Trelja...Of course, I jest a bit. Nevertheless I have never heard a ported speaker that I could not recognize, from its sound, as being ported. Although I prefer sealed boxes, and have built my subwoofer systems that way, I have never heard any box speaker that did not exhibit some degree of boxy sound signature. Which brings us to planars. The best speakers I have heard are electrostatic, but Maggies come close, and for practical reasons, that's what I have.

To each his own.

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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I sound like a broken record, but Sean makes a lot of good points.

While I also don't have a lot of experience with aperiodic enclosures, Bud is a big fan of them in certain instances. The transient response is supposedly improved, and the impedance curve is noticeably flattened - resulting in a more "resitive" speaker. Personally, as a tube guy, I don't get so panicked about high impedances (my Atmas love them) it's the low impedances I am more worried about.

The Fried Beta used an aperiodic enclosure, and Bud (who likes sealed boxes, just not as much as a TL) tells me it was the only way to get bass out of the small box. It makes the box size "appear" larger.

While I hope to do a lot of testing in the next 18 months, it would be interesting if we had some more A/B testing going on with between sealed and aperiodic boxes. Off the top of my head, I can't think of why a standard sealed box would be superior. And, you don't need to rely on Dynaudio or ScanSpeak's variovents. A lot of people just use a resin shower drain they get from a home improvement store, and foam or layers of gauze or felt.

Eldartford, as you said, "to each, his own", but I find the bass of electrostatic speakers to be less powerful and extended than a full range loudspeaker. They do have a lot of other niceties, though.

Cdc2,
As is always the situation, execution of design is at least as important as the design itself.
Good Question!