Triangular Waveguides

[Patrick Bateman]

Over the weekend I came up with what seems to be a fairly innovative (albeit obvious) waveguide geometry.

I really wasn't expecting this to work, but it looks like it does, so thought I'd share it here.

What I came up with are triangular waveguides. Attached are some photos of the waveguide, reports generated using ATH and ABEC, and the 'raw' predicted response.

Here's pics of the simulated waveguide, and what was simulated in ABEC (with an enclosure.)

normalized horizontal polar response and acoustic impedance

normalized vertical polar response and acoustic impedance

raw horizontal polar response

raw vertical horizontal polar response

If I were using one of these triangular waveguides in a project, I'd generally have the pointy end facing UP not to the right. If you're in the same boat, then when you look at these sims, swap the "horizontal" and "vertical" sims. Note that the horizontal and vertical response are virtually identical. Which was quite a surprise, I was expecting the triangular shape would cause the waveguide to be shaded towards the widest end. But as you can see in the sims, this doesn't seem to be the case.

 

[Patrick Bateman]

Here's the ATH model

The secret sauce is this formula here:

Coverage.Angle = 22 + 27*cos(1.5*p)^2 - 5*cos(p)^2

in particular, the fractional exponent gets you a waveguide with a number of sides that's equal to double the number here:

[angle] * cos ([number of sides]*p)^2

For instance, "45 * cos (1.5*p)^2 will get you a three sided waveguide

change the number to "2.5" and you'll get a five sided waveguide, etc

 

[luca4]

Definitely better than rectangular shapes, as I told you a few days ago ...

 

[mabat]

You can make an observation of the full radiation pattern on a spherical surface around the waveguide:

ABEC.SphericalField:1 = {
  Radius = 1    ; [m]
  Angle = 90    ; [deg]
  Density = 50  ; nr. of mesh elements
}

 

[Patrick Bateman]

Here's a few ideas on how these waveguides can be useful.

Triangular seem nearly ideal for putting a speaker into the corner of a room. A bit like the Klipschorns, but with a triangular waveguide you can keep the height to a minimum, since the angled baffle aims the wavefront towards the center of the room.

If using a two way, it also allows for the "Gradient Trick" of aiming the off axis nulls further out into the room, instead of having them right by the speaker itself.

 

[Mitch311]

I really like this shape aesthetically and the polar responses look great.
Would it also give you a correspondingly deeper loading due to a larger horn mouth? Compared to a 90 x 40 horn for example?

 

[Patrick Bateman]

Indeed. You can see it in the rise in the acoustic impedance.

A lot of that is because there's a diffraction slot (see the model attached in post 2)

 

[b_force]

Because of its shape, I am very curious about the HOM's (obviously in an OS waveguide)
What do you think @gedlee ?

 

[TNT]

raw horizontal polar response

There are 18 traces... is this every 5 deg or is it the full 180 deg panorama? Legend was missing. And as it is asymmetric, its of interest

//

 

[Patrick Bateman]

zero to 90 degrees in 5 degree increments. If you want to mess around with it, the config file is attached to post 2

ABEC.Polars:SPL = {
MapAngleRange = 0,90,19
Distance = 3 ; [m]
;Offset = 69
}

 

[TNT]

But then we only know the half of it as it is not symmetric around the vertical axis!? In this particular case, don't you have to do the full 180 to understand the WG directivity properties? It will not "sound" the same standing to the left or right of on axis...

For the speaker ngy4wG2.png, is the 90 deg data from the right or left side?

//