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Old 3rd September 2011, 01:44 PM   #291
Elias is offline Elias  Finland
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Quote:
Originally Posted by LineArray View Post
This will not happen as only a trumpet radiates like a trumpet,
i already explained that before with respect to other natural
sound sources i mentioned.
According to David S. it will apparently happen
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Old 3rd September 2011, 01:44 PM   #292
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Originally Posted by LineArray View Post


- diffusivity (enhance IACC in the listening rooms reverb)

Good news after all the bad is all listed measures of quality can be influenced by
modifying the room, but also by design and setup of loudspeakers.

As directivity and setup of stereo loudspeakers may be used to establish a suitable
balance between IDT, desirable amount of reverb and direction of first reflections, also
diffusivity may be introduced in a speaker.

But that kind of diffusivity should (if possible) be designed to not disturb phantom
imageing but selectively as possible increase IACC in the listening room's reverb.

Without too much of said unwanted side effects, that will be possible only at higher
frequencies. Because at those frequencies there is also the largest disbalance (in relation)
between natural and reproduced reverb's IACC, this may be worth the effort nevertheless.
Which should read "decreasing" the IACC instead of "enhancing" or
"increasing", sorry for confusing. Missed the timeline for editing ...
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Last edited by LineArray; 3rd September 2011 at 02:02 PM.
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Old 3rd September 2011, 01:54 PM   #293
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Originally Posted by Elias View Post
...

The problem in your approach: Toe in front of you and the speaker illuminates the contralateral wall maximally. Why purposely amplify the sound from the wrong side? The more smart way to do is to illuminate the wall of the same side, i.e. the right channel signal illumintes the right wall, and vice versa.

- Elias
That approach at least stretches ITD and decreases IACC with a given
directional speaker. Both would according to my previous post, enhance
quality of the listening room's reverb as experienced at the
listening position.

It does of course not solve the inherent problem with stereo, as
to my knowledge none of the strategies proposed in this thread does,
thereby explicitly including my own proposal of additionally utilizing
"controled diffusivity" in a loudspeaker.

It is a multi layered "drawback/benefit" balancing problem, no simple
solution available.
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Last edited by LineArray; 3rd September 2011 at 01:57 PM.
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Old 3rd September 2011, 02:06 PM   #294
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ScottG wrote

“I've done this before (on a putting green well away from trees). Both with directional and "omni" loudspeakers. In every case the more directional speaker was easier to localize.”

Hi Scott, for a loudspeaker to truly be “omni”, it HAS to radiate a spherical pattern and normally it has to be small enough not to have directivity over a broad band. As a result if you stood facing it, what arrives is essentially identical in both ears and so is harder to pin point it’s location in depth.
Most multi way speakers radiate a complex field or interference pattern that can be from diffraction effects, multiple drivers operating at the same frequencies or other things which cause a response which is different if you measure it say a foot away from the first measurement.
When this happens, one can “hear” the physical location in depth, the more complicated the radiation is, the more the speaker shouts “here I am 10 feet away”.

What I wrote about hearing while developing the synergy horns was that these DO radiate a spherical patch and so while the confine most of the energy to a given angle and little to the sides, what you hear in front is much more like an omni speaker in that there is little for your ears to localize as being say 10 feet away.

“This shouldn't come as any surprise though. We do use difference checking from one ear and the other and can detect minute changes in pressure (particularly at higher freq.s) at various angles.”

It is not only no surprise but is my exact point. When you can easily “hear” how far away the source is, it is because of those spatial differences and THIS greatly reduces the ability to produce a mono phantom image as the speakers image competes with the mono phantom illusion.

A hifi speaker company has also recently discovered that you can hear the way the speaker radiates.

KEF - Innovators in Sound

While their claim of being “the world's first single apparent source loudspeaker” is a total crock (we have been selling Synergy horns for 6 years and Unity horns 5 years before that), the explanation is real. Not only that but the Synergy horns can reproduce a square wave over a broad band, have a high degree of directivity and in spite of some having as many as 42 drivers, all radiate as a single source.
Best,
Tom

The result of getting all the drivers in a speaker powerful enough for one to fill a football stadium, to add together into one source, producing a homogeneous sound field, a first generation loss recording with a handheld camcorder. Try with headphones.

Videos Posted by Danley Sound Labs, Inc.: The Jericho Horn plays The Hunter [HD] | Facebook
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Old 3rd September 2011, 02:15 PM   #295
Elias is offline Elias  Finland
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Originally Posted by LineArray View Post
stretches ITD
What does it mean to "stretch" ITD?
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Old 3rd September 2011, 02:18 PM   #296
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suppressing early reflections
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Old 3rd September 2011, 02:19 PM   #297
Elias is offline Elias  Finland
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Originally Posted by markus76 View Post
Yes, wouldn't it be nice to be able to record, distribute and play back multiple discrete channels? Someone should invent such a system
Ambisonics have been already invented
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Old 3rd September 2011, 02:22 PM   #298
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Originally Posted by Tom Danley View Post
... a first generation loss recording with a handheld camcorder. Try with headphones.
Truly stunning ...
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Old 3rd September 2011, 02:43 PM   #299
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This has been a topic of considerable attention on my forum for years. (Decades)

My 2˘:

(Lifted straight off the Pi Speakers forum on AudioRoundTable.com)

From the following thread:Sometimes, I hear phrases like "prat," "soundstage" and this particular one - "making speakers disappear" - and I'm somewhat at a loss for what the person is trying to describe. Could be a lot of things, so I have to try and learn more about what they're experiencing or wanting to hear.

When I am asked what is required to make speakers "disappear" - my first thought is that I need to understand what it is the person asking considers to be acoustically "invisible." Is it that he wants the speakers to have flat response and low distortion, and thereby add very little to color the sound? Does he want envelopment, the illusion that sound surrounds him? Or does he want localization clues, imaging that seems to make each instrument originate in a different location in his listening room?

So when I was recently asked about "making speakers disappear," I set about asking questions, and listening to descriptions of what this person liked. At first, I thought he really didn't like the tilted up response of the loudspeakers he was talking about. But after a while, I realized that may be partially at fault, but what he was really craving was good stereo imaging. He wants a sensation that every instrument is coming from different locations in the room. After realizing that, I knew what direction to go.

Here's the deal. There are a couple of ways to do this in your listening room. One's a little more difficult, but moves closer and closer to recreating a sonic impression of realistic directional clues, and placing sound sources where they really are in the recording environment. The other easier method will not do this, but will give an impression of sounds coming from different places "on the soundstage" - depending upon all the variables of the interactions of phase relationships in the amplifiers, speakers and most importantly - in the listening environment, itself.

There are two things that contribute to form our aural positioning information. One is amplitude (volume loudness) and the other is phase. Both are related - a point source is heard by both ears, and there is a subtle amplitude and phase difference between them. If we're moving in the environment, there's a slightly different Doppler shift for each ear as well. So that's how we can distinguish the directions and distances of sound sources.

The most accurate way to create an impression of acoustic position, is to add point sources. If we run several microphones and then recreate the recorded sounds using several loudspeakers - as the home theater guys do - then we've generated more position information. If we're careful to match the microphone placement and the loudspeaker placement and directionality, we can really do good things with our "soundstage." And if we go to the trouble of minimizing reflections in the listening environment, we can go even further in this direction by reproducing the very subtle phase differences in the recorded signals.

Trouble is, that our listening environment smashes these kinds of clues with a sledgehammer. It's pretty difficult, really, to have such an "acoustically sterile" environment that it doesn't inject some of its own "soundstage components." We've got a lot of reflecting and absorbing and resonating surfaces. Children playing and dogs barking and the neighbor cutting his grass. In the theater, it's long walls and bunches of people chomping their popcorn and absorbing sound. So its hard to be "acoustically sterile." But that shouldn't stop us from going in that direction.

When working with two channels, there's a positioning trick I learned a long time ago that works very well. It goes a long way towards equalizing the amplitude clues between channels and minimizing phase clutter in the form of early reflections. The idea is to cross the forward axis of the two speakers just in front of the listening area. This is the natural setup of the Pi cornerhorns, and it is also a good way to position other speakers too. But the speakers must generate uniform off axis sound for this to work, otherwise, off axis listening positions will have an unnatural tonal balance.

In fact, that's one of the things that sets apart the Pi cornerhorns from Klipsch. Klipsch speakers are all designed to be listened on axis, and movement from the forward axis causes problems with the frequency response. This prohibits them from being setup with axis crossed in front of the listener, and in fact, strictly limits their best listening spot to a certain point in the room. The Pi cornerhorn provides even coverage on axis and off, so the reverberent field is uniform providing tonal balance. Because of this, there's a wide listening area where the sound is balanced between speakers both in terms of amplitude and frequency spectrum, and also directed to minimize early reflections, giving properly phased aural clues to listeners in this areas.

If you are listening at the point where the speaker axes cross, then the only place where the two speakers provide the same amplitude is when you are directly between them. The further left or right of center, the more difference in level between the two speakers. If you're forward of the axis-crossing point, the difference is even greater. But if you are behind the axis-crossing point, then movement away from a speaker brings you more directly in line with its forward axis, and moves you further from the forward axis of the other speaker. This has a balancing effect on the amplitudes arriving from each channel, and makes the area where channels are balanced much wider. Of course, this requires speakers that produce uniform directivity, which is one of the benefit of Pi Speakers.

When setup this way, the directional nature of the horns reduces early reflections. If angled inward enough, the horizontal pattern keeps the sound from being reflected off the nearest side wall. It's also best to sit away from the rear wall, if possible, and make it absorbent or diffuse. Bookshelves often work well.

That's one way to create the illusion of having the "speakers disappear." I think it's the best way, as it maintains the phase and amplitude relationships of the recorded material. Another way to do it is much simpler, but it makes no attempt to recreate the recorded soundstage. This method creates its own soundstage, which is not "accurate" if recreation of actual positions is important to you. It is, however, very pleasant and it does provide a sense of unique position for each instrument and sound that is generated.

Reflected energy, by its very nature, has a mix of phase relationships. The idea of the point source is that the loudest sound is presented directly from the transducer. Anything else has to travel further - to hit that wall or chair or cat - so it is greatly attenuated. This means that the components of the acoustic signal you hear the loudest, are the components that are generated by the speaker.

But the idea of reflected energy is that you don't know what you've got, but you know it has a unique phase relationship with the source. It's difficult to know exactly what it is - because there is literally an infinite number of phase relations possible. Reflect an inch down the wall, and phase is a little different than it was an inch back. Two inches, more different still. And we've got lots of little half inches and sixteeth inches and sixty fourths of an inch to think about in our 25 by 18 by 8 foot room. After we examine all of those, we still have to look at the tables and chairs and cats and dogs.

Using a lot of refected energy pretty much ensures that we'll create our own soundstage. It has nothing whatsoever to do with the original soundstage, but it does give an impression of spaciousness and it is very satisfying. Stuff is coming from everywhere.

The guitar player may be right in front of you. The singer is two feet to his left. The guy with the very low voice seems to come from ten feet away. These aren't anything at all like where they were originally standing, unless you read the Hitchhikers Guide to the Galaxy while you listen to the stereo - in which case they will all be in exactly the same spot as they were recorded, except upside down. But your system - the room and chairs and cats - will have created a "soundstage" with its own positioning information caused by the phase and reflected amplitude relationships from the room itself.

So when I was recently asked how to make a pair of Klipsch Heresy's "disappear," I realized what was being asked was how to improve imaging. Since they don't provide uniform directivity, we can't set them up with forward axis crossed in front of the listener without creating a tonal imbalance. But it may be worth a try, to see if the improved imaging is worth the loss of spectral balance. Try pointing them inwards, about 45 degrees to the wall, and see if you like 'em. If not, try 20 to 30 degrees. You'll probably lose some treble, because HF droops off axis compared with on axis, and it the HF loss is greater at 45 degrees than it is at 20 or 30 degrees. But you may be able to find an orientation that sounds good and provides greater imaging.

If not, try using reflections to generate an artificial soundstage. Take those Klipsch Heresy's and point them at the walls. It will increase a sense of envelopment, and make it sound like things are coming from everywhere. As much as we all joke about the thing said of Paul Klipsch and Amar Bose - where Amar holds his hands to form a horn to his mouth and speaks to Paul (referencing his horn ideas), and then Paul turns his back on Amar to reply (referencing his direct/reflecting thing) - you'll find an interesting "artificial soundstage" is created by just pointing your Heresy's directly 45 degrees into the corner. I guess that's sort of like Paul and Amar shaking hands. Give it a try, see what you think.
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Old 3rd September 2011, 02:47 PM   #300
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Ambisonics have been already invented
... just like all those other surround formats that are readily available in very cheap AVRs.
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