Interesting Dipole Surround Design - Thoughts?

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Peter The Greek

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Joined 2014
#1
G'day all,

In my quest to find a suitable surround speaker (to DIY), I stumbled across this:

http://www.google.co...s/US20110158445

US20110158445A1-20110630-D00004.png


Lets just assume a "di-pole" rear is a good idea.....I dont want to get into a di v mono discussion

What do you think about the waveguide?

I will have some AE TD8's to use with these, I thought perhaps I could couple with one of the Mundorf Dipole AMT's (the big one), cross at around 2khz. 2 way only.

Thoughts?

Here is the off the shelf version:

Steinway Lyngdorf - Model LS Surround

An externally hosted image should be here but it was not working when we last tested it.


Cheers.
 
#2
Well this is the most strange speaker I have seen!. If the goal was to create a diffuse and non-uniform soundfield, I guess the mission was complished😀

ps. I read the tech details from the homepage and YES to my guess above. "The innovative patent-pending AER (Ambience Enhancing Radiation) refers to the ability of the dipole tweeter design to disperse the treble in a way that achieves an enveloping and ambient sound throughout the entire listening room." (they have several ways of doing this, in differrent models.

A DIY version would be piece of cake, but who on earth knows what kind of measured performance to aim for??? Fully controversial to so called hifi speakers at least.
 
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#3
Peter, I could be missing something but I see nothing to indicate that this is a dipole design.

With the pair of spaced mid drivers the horizontal directivity is going to be rather narrow, particularly as we approach the tweeter crossover frequency.

The AMT tweeter seems to have its null axis aimed at the listener, so all that we hear is due to reflections from what appears to be some kind of waveguide, but is actually just a pair of reflecting surfaces?

A very peculiar design.

Keith
 
#4
Keith Taylor said:
Peter, I could be missing something but I see nothing to indicate that this is a dipole design.
Keith
Click to expand...

I agree that this is likely not a dipole speaker.
It's listed as a 2-channel surround speaker and it would make sense that there are 2 planar tweeters with their closed backs against each other. I assume it's 2 controlled directivity channels in the same box.

The spec sheet lists a single planar tweeter in that speaker which is puzzling. Steinway Lyngdorf are known for their competent designs, I assume it's a spec sheet typo and that they are not using a single tweeter to output 2 channels.
 
#5
On the manufacturer's website they have LS models for either in-wall or free-standing (in-room) applications. The Model LS Surround is listed on the in-wall page. Hence, that particular enclosure is not likely a dipole design. Their free standing speakers are dipolar. Likely, you could use in-wall surrounds with the in-room tall line arrays if you needed surrounds.
 
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#6
The tweeter is dipole its a single open backed AMT.

Not sure how they wire the mids....possibly in opposite phase.

Its an interesting design, but the only tweeter that I could do it with in 2-way is rather expensive.....quite a punt (the mundorf amt 27d)
 
#8
Peter, my point is that the LS Surround and all of the other components in the in-wall series are described on the manufacturer's website as in-wall mounted items. Carefully read the description of the speakers on that specific page. Notice also that their large dipole icon is not shown at the bottom of the page in the row of icons for their speaker line. None of the LS in-wall speakers are dipolar.

AMT tweeters from several makers often offer a rear housing that can be used for monopole applications or removed for dipole operation.
 
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#11
Peter, the acoustic waveguide simply adapts their dipolar AMT tweeter so that its rear wave is radiated forward instead toward the rear. The spacing is critical so that the rear radiation supports the forward radiation from the AMT instead of cancelling it. Even for this in-wall application the LS Surround is not claimed by the manufacturer to be dipolar.
 
#13
"Loudspeakers suited for reproduction of stereo channels or front channels of surround sound signals are normally designed to provide a precise reproduction of high audio frequencies directed towards the listener. Hereby the influence of room reflections at high audio frequencies is suppressed relative to the direct sound reaching the listener, and this results in a rather precise audio image in front of the listener. Most often, loudspeakers used to reproduce surround and back channels in surround sound systems are traditional small hi-fi loudspeakers with high frequency drivers directed towards the listener. However, in fact such loudspeakers are not suited for optimal reproduction of surround and back channels, since these channels are intended to provide the listener with a rather diffuse spatial effect and not a precise localization. Thus, to obtain this, it is preferred that the listener is unable to locate the position of the surround and back loudspeakers. In other words, it is preferred that these loudspeakers provide a diffuse sound reproduction which is not directed towards the listener. This is especially important at mid and high audio frequencies, especially above 2-3 kHz."

The null on-axis makes sense after reading the patent. This speaker must be positioned in a way that it radiates into the walls and the listener is hearing the reflections.
 
#14
The implementation I deduct from the patent is that the waveguide reflects the rear emission from the AMT. The AMT likely works in the frequency range 2 kHz on up area as suggested within the patent. Nothing in the patent suggests to me that the entire speaker enclosure radiates into the walls just that the AMT is spaced appropriately such that the waveguide emits the proper reflected waves.
 
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#15
Right, the patent talks about the waveguide producing a "difuse sound field" with an on-axis null.

I take that to mean that the front and rear radiation of the AMT tweeter arrive at the listener after reflecting from the walls perpendicular to the wall the speaker is installed in.

The patent doesn't specify the operation of the 2 midrange drivers. I assumed that if they are wired out of phase they would extend the on-axis null further down in frequency.
 
#16
I think this patent is not applicable to the speaker in the opening post. This kind of layout is use in S-L stand-alone models, not on-wall models. The patent rsults is something like cardioid dispersion pattern.

The "problem" with all S-L speakers is that they use very different radiation systems, every speaker radiates differently. LS and S series use AER system but LS-surrond is completely different. It is very difficult to understand how each speaker works, and fancy marketing names are used to describe function.

Somethng like this can be heard when you connect eg. left tweeer of a 2-way stereo speakers in reversed polarity! It sounds "nice" with some music and sure it adds "air and space" in reproduction! But measured response looks like roller coaster!
 
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#17
I want to add that during '80s many stereo systems had "Enhanced Stereo" switch - now we have "spatial effect" or multichannel digital signal processors to do this. Mostly these system mess with phase/delay of different frequencies to make soundfield "larger" or more "spacious". Because of wavelenth these effects occur mostly above say 1000Hz. The funny thing with stereo enhacement is that even a very small head movement makes sounds move a lot!

Read more here
Spatial enhancement for immersive stereo audio applications | Andreas Floros - Academia.edu
Ambiophonics - Wikipedia, the free encyclopedia
Enhancing Stereo
 
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