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The question that brought me here. Klipsch WDST. Gimmick or not?

2Sunny

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As part of my recent upgrade journey I initially purchased a pair of RP-600M II speakers because I read that bipole speakers should not be used in an Atmos setup and I believed my RP-250S speakers were bipoles. I tried both pairs of speakers and listened to scenes from Midway, Unbroken, Incredibles 2, Roma, Blade Runner 2049, and Harry Potter Chamber of Secrets and suprisingly I did prefer the sound stage with the RP-250S by a wide margin as I found the sounds from the 600s too directional whilst the sounds from the 250s more all around the back of the room. THEN I found out that Klipsch says the RP-250S speakers use a proprietary technology called Wide Dispersion Surround Technology that makes them neither bipole nor dipole, but rather something unique. Which brought me to my question:

Is Klipsch WDST a gimmick or does it really work as advertised and has anyone ever tested it?

My very limited one person experience seems to indicate it's true.

What Klipsch says:
"There are three "common" types of surround speakers available today plus some unique types created by different speaker manufacturers. "Monopole" speakers consist of a speaker or group of speakers all firing on the same plane in the same direction. This includes the vast majority of all speakers made. What people think of as "normal speakers" are termed Monopole. With regard to current surround sound formats, monopole speakers are the least desirable because they are the least effective in creating an "enveloping sound field" (ambience). They are good at localization, but that alone is not enough to produce the desired surround effect.

If you take a monopole speaker and add another speaker placed 180 degrees opposite of it (i.e. back to back) firing in the same phase, you have a "bipole" speaker. Firing in phase means all drivers on both sides are at the same excursion point at the same time. This creates the exact same sounds coming from both sides of the speaker at the same time. By design, Bipole speakers send no sound directly toward the listener. A bipole speaker will produce good "ambience" as all the sound is reflected off the walls of the room, but is not effective in producing "localized" sounds.
If you take the basic design of a bipole speaker with the rear facing drivers firing exactly opposite of the front, you have a "dipole" speaker. Dipole speakers produce a very diffuse sound, which is good for ambience, but, like bipoles, are not very effective at localization. Dipole design further reduces direct sound to the listening position.

Both bipole and dipole speakers should be mounted on the sides of the listening position and use reflected sound off of the walls to produce their effects. So if monopoles can offer localization but not enveloping ambience, and bi-pole/dipole speakers deliver ambience without localization, what can provide both important characteristics at the same time?

Klipsch produces a unique surround speaker that utilizes a technology called Wide Dispersion Surround Technology (WDST™). Each WDST™ enabled speaker contains two Tractrix® Horn drivers and a woofer. Each horn covers a 90-degree arc and the combination of the two covers a full 180 degrees. This coverage gives excellent ambiance without having to use the walls to reflect sound. The controlled pattern of each horn (what we call "controlled directivity") leads to excellent localization of sounds because there is sound directed at the listening position, regardless of where in the room you are seated. And because the WDST™ surround speaker does not rely on wall reflections, it can be mounted in many different places in a room, leading to greater flexibility with placement. It is rare to have perfect side-wall positions available due to the placement of doors, drapes, furniture and such. WDST™ design delivers enveloping ambience WITH localization for the ideal surround sound result AND gives you the flexibility of placement to solve room design problems."
 
They are bipole speakers. There's nothing special about them AFAICT and that design is not unique to Klipsch. The effect they are talking about is probably real, as long as you ensure that you are more or less on-axis to one of the poles. Then you should get (some) localization queues while also getting the sound bounced around the room.

Is it a gimmick? Sure, I suppose. Surround sound mixes are not designed with bipoles in mind. But if you like it, you like it.
 
I was not able to find a proper assessment of a Klipsch WDST speaker.

However, these kinds of designs tend to have wildly inconsistent directivity patterns due to interference:
SPL Horizontal Contour Normalized (2).png

One can use acoustic lenses to minimize crosstalk and homogenize the directivity as best as possible, but Klipsch does not appear to have that technology.

Here for example the Sonos Era 100 with acoustic lenses covering the tweeters:
Unbenannt-4-2 (1).jpg
 
They are bipole speakers. There's nothing special about them AFAICT and that design is not unique to Klipsch. The effect they are talking about is probably real, as long as you ensure that you are more or less on-axis to one of the poles. Then you should get (some) localization queues while also getting the sound bounced around the room.

Is it a gimmick? Sure, I suppose. Surround sound mixes are not designed with bipoles in mind. But if you like it, you like it.
So am I correct in saying that the "technology" is simply that they have placed the horns at 90 degrees apart instead of 180 degrees opposed? Are there speakers out there with 180 degree opposing faces?
 
So am I correct in saying that the "technology" is simply that they have placed the horns at 90 degrees apart instead of 180 degrees opposed?
Yep.

Are there speakers out there with 180 degree opposing faces?
Seems like the 90 degree thing is much more common than the 180 degree design these days. And non-bipole is much more common in general. I was able to find a definitive tech speaker Dymension DM70 that uses a rear tweeter though.

These are dipole (out of phase), not bipole (in phase), though, right? I looked around on Google and didn't find too many true bipoles.

I don't think they're popular because you're basically sticking two speakers together back to back (costly in terms of drivers, anyway) for a questionably beneficial effect.
 
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