~ Sunshine ~ - Page 3 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th April 2012, 08:18 PM   #21
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
I don't have any data on that. I know that the results that I saw were not very impressive. My point here is simply not to assume that such and such a technology works because straight lines drawn on paper look so good. You have to provide decent measurements of the device or its just a guess how it will really work.

Basically the higher the frequency the more valid ray-tracing is, but also the more difficult it is to predict how the rays are emited from the source. So basically when the source and the device at a larger than a wavelength but not much larger than several wavelengths.
  Reply With Quote
Old 7th April 2012, 09:38 PM   #22
diyAudio Member
 
Join Date: May 2003
Location: Washington State, USA
Quote:
Originally Posted by gedlee View Post
The world would be a much simpler place is we could do acoustics by simply drawing straight lines. Problem is that sound is waves not light rays and they don't work like light rays. They go arround corners and diffract at edges, all kinds of things that "rays" do not account for. So I simply discount any argument that uses "rays" to explain what happens. Like the "acoustic lens" thing that was shown earlier. Measurements of a real device show that it doesn't act much like it is supposed to except over a very narrow range of frequencies. But thats OK, it looks cool and marketing likes that - so it doesn't actually have to work. The real disappointing thing is that the techniques that actually do work aren't all that "cool" looking and tend to be much larger than we would like. So its just easier to do it wrong and looking good.
What are we to make, then, of Figure (2) and the surrounding discussion found on page 6 on the .pdf of this document?

http://www.gedlee.com/downloads/Philosophy.pdf
  Reply With Quote
Old 7th April 2012, 10:47 PM   #23
diyAudio Member
 
Join Date: Apr 2005
Location: Sitting behind the 'puter screen, in Illinois, USA, planet earth
Hi Art
The issue of hf absorption is a daunting one yet any improvement over what is available is appreciated. The only solution that seemed practical as a first shot was this one, a huge CD horn, a combination of a specific narrow pattern and lotsa driver horse power. I agree with a couple of your observations but can’t discuss them :-)

Hi Earl, all
What I was trying to explain earlier in this thread was that an acoustic reflector based system has the problem that the physical reflector is a fixed size while the frequency span means that the acoustic size is larger at higher frequencies and smaller at lower frequencies.
How large the reflector is acoustically governs how it reflects until it is very large where it acts more like a mirror (as in Earls Fig2) or it is very small like a small fraction of a wavelength where the pressure goes around the object.. The Paraline thing mentioned here uses path length only, no reflections and bends in the plane where the dimension is a fraction of a wavelength at 20Khz.

In the communications horn example earlier, the reflector is large enough compared to the wavelength to convert the expanding spherical wave into a plane wave beam with an off axis parabolic reflector.

The Zenith “circle of sound” speakers looked pretty cool back then anyway.

Heatmiser
I would agree with the link in general and would underscore the sound following the dotted lines are in stereo imaging terms “bad juju” but would add if you can position the far wall bounce to be behind you, that good too.

An equal loudness balloon would more clearly show why this kind of aiming works to maximize the width of the sweet spot (like if you have a couch) with any directional speaker and this works with narrower patterns as well..
Best
Tom Danley
__________________
Bring back mst3k and futurama
  Reply With Quote
Old 9th April 2012, 04:28 PM   #24
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by HeatMiser View Post
What are we to make, then, of Figure (2) and the surrounding discussion found on page 6 on the .pdf of this document?

http://www.gedlee.com/downloads/Philosophy.pdf
There are instances where ray tracing works, but yes, in ALL cases we have to consider the diffraction and non line-of-sight issues. In general when one is dealing with devices placed very close to the source then ray tracing is at its worst. For eample, in my drawing, the diffractions off of objects nearby the source will not be accurately represented. When ALL of the rays are the result of interactions near the source then things become very tenable indeed.
  Reply With Quote
Old 9th April 2012, 04:40 PM   #25
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by gedlee View Post
For eample, in my drawing, the diffractions off of objects nearby the source will not be accurately represented. When ALL of the rays are the result of interactions near the source then things become very tenable indeed.
Earl,

The definition of "tenable": “Capable of being maintained in argument; rationally defensible: a tenable theory.”

What rationally defensible device has an output with ALL rays that are the result of interactions near the source?

Art
  Reply With Quote
Old 9th April 2012, 05:32 PM   #26
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego

A question for Tom Danley, if he's following this thread:

In the paraline patent, there's a picture of a paraline with a compression driver *and* four midranges mounted to the back plate.

You'd mentioned that you built one of these, but hadn't released it.

Did it function as expected?

The reason that I ask, is that it seems that a significant fraction of the midrange energy would arrive out-of-phase.

I understand that the dimensions of the paraline are so small, that the midrange wavelength will not expand until they exit the throat.

BUT

The midranges are still radiating in 360 degrees, so a significant fraction of the midrange energy will be delayed, as it basically 'bounces around' inside of the paraline.

I can see how this *wouldn't* be a problem for the compression driver, because the compression driver is mounted right in the center of the device. But it seems like it would be an issue for the mids, since they're mounted off axis.

To my eyes, it seems to be similar to the problem in the Synergy horn, where a notch appears at a predictable frequency because their energy reflects off the throat. But the difference in the paraline is that the distance is much further, because the width of the paraline is acoustically significant.


This would probably make more sense if I included a diagram, but I hope that was clear enough. I like the idea of having five drivers inside of the paraline, but I can't see how it would work.

  Reply With Quote
Old 9th April 2012, 05:46 PM   #27
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by weltersys View Post
Earl,

The definition of "tenable": “Capable of being maintained in argument; rationally defensible: a tenable theory.”

What rationally defensible device has an output with ALL rays that are the result of interactions near the source?

Art
Opps, meant "untenable", well really "questionable" or "doubtful".
  Reply With Quote
Old 10th April 2012, 01:50 PM   #28
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by gedlee View Post
Opps, meant "untenable", well really "questionable" or "doubtful".
In other words, tenuous .

So what "questionable" device are you writing about that has an output with ALL rays that are the result of interactions near the source?

Art
  Reply With Quote
Old 10th April 2012, 02:30 PM   #29
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Got tongue-tied!

Most of the drawings shown earlier in this thread had a device placed very close to the sources and used rays to show the effect of these devices. Very questionable technique that. (So I guess that I meant that the analysis technique was "tenuous" not the device.)
  Reply With Quote
Old 17th April 2012, 04:38 PM   #30
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by Patrick Bateman View Post
Click the image to open in full size.
As noted in the first post, the 'neat' thing about these inventions is that they give you directivity control that's similar to a long deep horn, but without the brutal space requirements. For instance, one of the Paraline devices has a depth of about an inch, and claims to have the directivity of a horn which is over a meter long. (According to the marketing literature.)

The way that this is achieved is by using a clever reflector. Basically the driver faces upward, and the sound is reflected ninety degrees. The pic above, from the paraline patent, illustrates how this works.

Click the image to open in full size.
If I'm not mistaken, the same math can be used to build your own S.A.W. lens.

Click the image to open in full size.

I took a stab at modeling one of these in Xara, using the dimensions from the patent.



Click the image to open in full size.
Click the image to open in full size.

This is a bit random, but Tupac Shakur was 'resurrected' via 3D animation, a trio of projectors, and a pile of mylar last week:

2PAC ALIVE Feat Snoop Dogg at COACHELLA 2012 (Tupac Hologram) - YouTube

Tupac coachella 2012 - YouTube

I used to work in a video arcade when I was in college, and we had a machine that pulled off a similar trick. It's called "Time Traveler", and it was made by Sega:

Sega's "Hologram" TimeTraveler coin-op Press Coverage (circa 1991) - YouTube

The thing that's amusing about it - is that it's basically very similar to the acoustic reflector that's detailed in this thread. I took our Time Traveller machine apart, and was amused to find that the 'hologram' trick is very very simple. There's a Sony Trinitron television mounted in the based of the cabinet, and a black mylar spherical mirror is set in front of the television set.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
some pics of the mirror and the game it came from

To complete the illusion, a layer of smoked glass is placed on top of the whole contraption. The smoked glass obscures both the television set and the spherical mirror. So all you see is the reflected light from the spherical mirror, and the 'holographic' image seems to float above the glass. (Check out the youtube video to see what I'm talking about.)

If I'm not mistaken, it's the same technology used in the Coachella video. The main difference is that they used three 1080P projectors instead of a television set.

I'm too lazy to draw up a diagram, but it's the same idea as the paraline. In the Sega game, the TV and the mirror are underneath the glass, and the image is projected vertically. (The light from the TV is bent 90 degrees, and goes straight up.)

In the Coachella 'hologram', I'd guess they did the same thing. The only difference is the scale. You'd need a concert stage that's transparent, and the projectors are *under* the stage, which then bend the light at a 90 degree angle to create the hologram, which shoots straight up.

It's a neat trick as long as the content of the is two dimensional, such as fighting games or climbing games. (Street Fighter II, Mario Bros, etc.)

Or someone pacing the stage, like in the Coachella stunt.

If the content is 3D I imagine the wavebending would get distracting.

And again, if you look at the schematic of the paraline from the patent, the idea is the same. Instead of a speaker as the source, it's a television set.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 11:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2