Horns and Waveguides

[Nestor]

I've been seeing these two terms interchangeably lately.

Other than the Tractrix™ used in Klipsch, who else uses what can properly be termed a "waveguide"?

[jcl]

Trick question? A horn is an acoustic wave guide, no?

JBL uses wave guides that are not billed as horns...
Genelec and Focal too...

[GranteedEV]

I've been seeing these two terms interchangeably lately.

Technically, all waveguides with a pattern control under 180 degrees, will act to some extent as horns secondarily.

Other than the Tractrix™ used in Klipsch, who else uses what can properly be termed a "waveguide"?

The goal of a waveguide - directivity.
The goal of a horn - increased efficiency.

Now a flat loudspeaker baffle, to start with, is a 180 degree waveguide. In one sense, you could even argue that it's increasing efficiency - a sufficiently small driver in free space (4pi) will be 6db less efficient than a driver operating in a baffle (2 pi). As the driver shifts from 4 pi space to 2 pi, it experiences in increase in SPL.

Now the problem with 2 pi space, is that tweeters will have a lot of off-axis energy. So by redirecting that off-axis energy forward even more, you will get some SPL gains in the forward axis. However the main goal of a waveguide specifically is to reduce the energy radiated to the sides - because a tweeter will just about always "spray" more energy into the sides than a, for example, 6.5" midrange would (which is starting to become directive even by, say, 2khz.

So the goal of the waveguide is to make the tweeter load the room similarily to the midrange, at the crossover point.

And since the waveguide inevitibly doubles as a horn, you might get some improved efficiency, though not necessarily throughout the entire passband.

However remember, not all horns will control directivity. A bass horn for example, will have a mouth which is acoustically smaller than the wavelengths being reproduced. Thus a bass horn will be omnidirectional, but still a horn.

Given all of the above, there's scenarios where you can use the term interchangably. Generally the deeper the throat portion, the closer it is to being a "horn". The shallower it is, the more it's probably a waveguide. But it's entirely possible for it to be "both". Generally wherever there is a compression chamber, it is a horn. A waveguide speaker can certainly have a compression chamber.

So let's see:

NO waveguide:


180 degree waveguide:



~120 to 90 (?) degree waveguide - will incidentally have some horn behavior



~50 degree waveguide / also a horn



back loaded horn / not a waveguide



LeCleac'h horn - only a waveguide incidentally, and its pattern is increasingly beamy rather than constant.



SEOS-15 waveguide - just as a contrast to the above:

[GranteedEV]

One other thing i'll add, is that the threshold between a pure "horn" and a pure "waveguide", is measurable in the Z-chart. A waveguide will have the same impedance whether a driver is on a flat baffle or not, and a horn will change the electrical impedance (by virtue of changing the acoustic impedance).

[Irishman]

I've been seeing these two terms interchangeably lately.

Other than the Tractrix™ used in Klipsch, who else uses what can properly be termed a "waveguide"?

Andrew Jones used waveguides with his tweeters in the value Pioneer line he did last year, and, I believe, on the new models for this year, due out sometime next month.

[Nestor]

One other thing i'll add, is that the threshold between a pure "horn" and a pure "waveguide", is measurable in the Z-chart. A waveguide will have the same impedance whether a driver is on a flat baffle or not, and a horn will change the electrical impedance (by virtue of changing the acoustic impedance).

IMO this is the key difference between the two.