[opnly bafld]

Secondly the dipole sound propagation of open baffles produce a big, diffused, remote soundstaging that isn't what is heard in the recording studio.  Like it or not, we're "married" to the entire recording process and to get optimal performance our playback systems must learn within all those given parameters.

Not all dipoles sound like you describe... aa

George

I agree George, none of the OB speakers that I have heard fit that description.

Lin

[sunshinedawg]

sunshinedawg - and everyone else arguing about this - please answer one simple question for me.

Is your goal:

a) to reproduce what you would hear if you were at the recording venue, or

b) to reproduce what you would hear if the musicians were performing in your living room?

Those are often totally orthogonal goals, getting close to either requires very different equipment and setup, and this conversation is rather pointless until you clarify that.

I understand it is impossible to exactly reproduce a live event. I want something close to a). My room acoustics are not Carnegie Hall, I'm not interested them, they are not noteworthy.

In my setup, I could get close to b) as well. I would just take down all my room treatments and disconnect my ambient channels, leaving my front crosstalk canceled speakers to interact with my room, but my room would sound really bad!

[JeffB]

Around 1986 or so Polk had something they called SDA(Stereo Dimensional Array). 
SDA supposedly improved stereo imaging through some cross-over trick that
sent some information meant for the right speaker over to the left and vice-versa.

Here is a link with tons of marketing speak.
http://www.polkaudio.com/homeaudio/products/srs12tl/

A friend of mine bought 2-way stand mount design with this technology.
The imaging was quite exceptional.
Polk says they gave up on this technology because it was too hard to properly market these designs in the era of declining high end audio stores.

I am surprised that I have never seen anybody else do this.  In fact I have never seen any mention of this technology as good or bad.

I can remember Polk stating that 2D stereo had many flaws and in fact was never really implemented quite as intended.  SDA was suppossed to get closer to the original concept.

I am speaking from vague recollection of Polk marketing speak.  I know nothing about this myself.

[opaqueice]

I understand it is impossible to exactly reproduce a live event. I want something close to a). My room acoustics are not Carnegie Hall, I'm not interested them, they are not noteworthy.

In that case, a dead room with two quality stereo speakers in the traditional arrangement is the best, IMHO.  That's what recording and mixing engineers expect (as the best case at least), and they make stereo recordings with that in mind.

Better yet, a decent binaural recording through phones.  That blows away any speaker system I've ever heard in terms of imaging, even through cheap phones playing an MP3 downloaded off the internet. 

Try it.

[sunshinedawg]

Around 1986 or so Polk had something they called SDA(Stereo Dimensional Array). 
SDA supposedly improved stereo imaging through some cross-over trick that
sent some information meant for the right speaker over to the left and vice-versa.

Here is a link with tons of marketing speak.
http://www.polkaudio.com/homeaudio/products/srs12tl/
A friend of mine bought 2-way stand mount design with this technology.
The imaging was quite exceptional.
Polk says they gave up on this technology because it was too hard to properly market these designs in the era of declining high end audio stores.

I am surprised that I have never seen anybody else do this.  In fact I have never seen any mention of this technology as good or bad.

I can remember Polk stating that 2D stereo had many flaws and in fact was never really implemented quite as intended.  SDA was suppossed to get closer to the original concept.

I am speaking from vague recollection of Polk marketing speak.  I know nothing about this myself.

From your link:

"Years ago Polk Audio recognized the importance of more absolute separation of information reaching each ear. Of course, the fundamental concept of stereo reproduction is that there are two separate channels of information, each intended for one ear only (i.e. "true stereo").

Sounds like exactly what I'm doing with my mains, but reading through it quickly, I couldn't figure out how they were achieving this.

[Russell Dawkins]

Take the right speaker for example. What Matthew Polk was doing was feeding the right channel signal to the left hand line array of 4 X 6 1/2s, then feeding an attenuated signal of inverse polarity of the left channel to the right hand line array, again, of the right hand speaker.

The idea is that the inverted, attenuated signal from the right hand array of the right speaker will reach your right ear at the same time as the signal from the left speaker reaches your right ear, so it is canceled. The effect is intended to be the absolute cancellation of the crosstalk, as with headphones.

This is based on the fact that as the signal goes around your face to the opposite ear it is delayed and the signal in general is attenuated, particularly the highs.

Simple, huh? 

[JeffB]

I found a better link explaining SDA.
http://www.polksda.com/srsreview.shtml

[dorokusai]

Jeff - Thanks for posting those links. I have an even older explanation that I can't find at the moment but will look for it and get it posted for those who are interested.

The 2-way design you referred to earlier was either the SDA CRS or SDA CRS+. It was a stand mounted, "bookshelf" loudspeaker. The CRS used an SDA tweeter as well as an SDA midrange but could sometimes sound pretty odd. Sometimes the soundstage was so large, the high end would often "throw" an instrument note or high level tone outside of the soundstage and cause you to look around at times. It was not natural IMO and the dimensional tweeter was dropped from 1986+, and the SDA idea restricted to the midrange region only.

I'll look for that other information but here's some material from the studies done on SDA + Surround Sound.

SDA Surround Technology Explained
http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf

Mark

[Toka]

SDA's are still popular for a reason...I will forever own a pair if I have say-so. Nothing quite like them, even to this day.

[csero]

Check out US patent # 7072474 for a more up to date and accurate electronic realization. This is what I use too. This is about crosstalk cancellation. The ambience part is a similarly long story.

[Mag]

Although I use ten speakers as well, my approach is based on an article I read several years ago either in a mag or on the net, don't remember which. It was a group experimenting with speaker placement. A large bass woofer, placed one on each side of the listener with the tweeters placed in front of listener.
So I tried this with just tower speakers in my living room placed 6' to the side and I thought it sounded cool. I wasn't really perceiving the sound directly from the speaker, but perceived it to be coming from in front, and the soundfield was huge.
I never implemented the idea as having speakers placed in the middle of my room was impractical.
After several noise complaints I decided to move my stereo to the basement, to better contain the sound. This room is long and narrow and I used the typical front,rear speaker placement with center channel.
Over time I became bothered by the narrowness of the sound. So I thought I'd try implementing the side of ear speaker placement, albeit modified. Placing my floorstanders perpendicularly to the side was okay. The room being wide now going lengthwise, left a noticeable soundfield gap,between speakers. So I continued to add speakers so that there was no apparent soundfield gap.
Basically what I have now,is stereo with 3 speakers left, 3 right, and matrix ed center and rear. The rear speaker wasn't necessary but I found placing it facing the wall in front of me,(all I have space for) made music sound fuller, particularly vocals.
Played at loud spl levels I would say that my setup closely simulates sitting in front of an amplified band in a bar or nightclub. At least to my ears.
When I listen to a two-channel stereo in a typical room of people's homes. I readily notice the narrowness of the soundfield, even though the speaker may sound great.
Perhaps if I get to travel someday and hear 2 channel stereo in an ideal room, my opinion would change.

[csero]

Perhaps if I get to travel someday and hear 2 channel stereo in an ideal room, my opinion would change.

The problem is - and it is also really hard to admit - that there is no ideal room for stereo reproduction if the recording venue is acoustically different from the playback room.

[Wind Chaser]

There seems to be a mindset about how speakers should be set up so the axis cross in front of the listener.  With conventional enclosed boxed speaker that seems to be very true, but in my experience with every dipole I have tried that arrangement does not create the most cohesive soundstage.  Common rules and schools of thought only pertain to common design and do not apply to OB.

[Russell Dawkins]

Jeff - Thanks for posting those links. I have an even older explanation that I can't find at the moment but will look for it and get it posted for those who are interested.

The 2-way design you referred to earlier was either the SDA CRS or SDA CRS+. It was a stand mounted, "bookshelf" loudspeaker. The CRS used an SDA tweeter as well as an SDA midrange but could sometimes sound pretty odd. Sometimes the soundstage was so large, the high end would often "throw" an instrument note or high level tone outside of the soundstage and cause you to look around at times. It was not natural IMO and the dimensional tweeter was dropped from 1986+, and the SDA idea restricted to the midrange region only.

I'll look for that other information but here's some material from the studies done on SDA + Surround Sound.

SDA Surround Technology Explained
http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf

Mark

As clearly seen in the illustrations in the link provided by JeffB, there is one little hitch in the theory as far as I can see, and that may be explained by the fact that in the hypothetical paths shown from the drivers to the ears of the listener, only one path is shown from the "dimension array" to the listeners' ears, not two as would actually be the case.

In other words a 2nd correction signal could be arguably required to correct for the 1st correction signal for the very same reason a correction signal was employed in the first place.

The absence of that signal (and, of course, it would be impractical) could account for the occasional sound being "thrown" out of the soundstage as you describe, Mark.

And in response to this from WindChaser:

"Common rules and schools of thought only pertain to common design and do not apply to OB."

I think the toe in technique does (and should) work with OB as well as with omnipolar speakers.

I imagine Clayton Shaw has tried a few demonstration configurations and seems to have settled on just this arrangement, probably because it works for the usual reasons and in the usual way - by broadening the sweet spot.

I have read a few comments on the demos to the effect that one notable characteristic of the set up was that the stereo image was stable as one moved around the room.

[sts9fan]

I was thinking  and I was wondering if this at all homogenizes the sound.  Honestly I think I rather let the media speak for it self.  Then there is the fact that you may be placing the sound but they are always placed in the same spot for every recording.  A three piece band is still coming from the same 10 degree separated speakers as a 12 person band.  Is it possible that a stereo set up with a center image could better place band members of varying numbers in space because of a larger separation of the speakers?

[csero]

As clearly seen in the illustrations in the link provided by JeffB, there is one little hitch in the theory as far as I can see, and that may be explained by the fact that in the hypothetical paths shown from the drivers to the ears of the listener, only one path is shown from the "dimension array" to the listeners' ears, not two as would actually be the case.

In other words a 2nd correction signal could be arguably required to correct for the 1st correction signal for the very same reason a correction signal was employed in the first place.

You are right, most of the older and simpler XTC are not recursive and/or based on simple delay-eq shemes. The solutions are much more refined nowadays.

[csero]

I was thinking  and I was wondering if this at all homogenizes the sound.  Honestly I think I rather let the media speak for it self.  Then there is the fact that you may be placing the sound but they are always placed in the same spot for every recording.  A three piece band is still coming from the same 10 degree separated speakers as a 12 person band.  Is it possible that a stereo set up with a center image could better place band members of varying numbers in space because of a larger separation of the speakers?

I think you misunderstood. The 10 deg speakers with XTC are creating a vavefront which resemble much more closely to a wavefront created in the front stage by a real source than any stereo setup.
3D hearing based on 4 things: ITD, ILD, pinna filtering and - most importantly - consistency of the 3 in case of head movements. Equilateral triangle can reproduce only ILD and some ITD in the bass range, and even that quite badly.
With XTC sound is not coming within the 10 deg, but seems to eminate from anywhere from the front.

Check out these vav files:
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track1.wav
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track2.wav
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track3.wav
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track4.wav
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track5.wav
http://www.isvr.soton.ac.uk/FDAG/VAP/wave/track5.wav

Just follow the instructions in the first one for speaker setup: " Ideally, you should sit 2m away from the loudspeakers directly in front of them. The centres of the speakers should then be approximately 35cm apart. If your speakers are very small, try to sit 1m away from them when their centres are 20cm apart. If possible, you should position the loudspeakers in the middle of the room; the fewer reflections you get from the acoustic environment the better."

[opaqueice]

I think you misunderstood. The 10 deg speakers with XTC are creating a vavefront which resemble much more closely to a wavefront created in the front stage by a real source than any stereo setup.

Can you explain that comment?

It sounds as though you're assuming that all the sound is emanating from a source that's small compared to the distance to the listener.  I guess that might be true sometimes, like for a solo instrument or singer, but usually it's not true at all (think of being in one of the front rows listening to an orchestra or jazz ensemble).

Furthermore in symphony halls most of the sound you hear is reflected, not direct, so even if you were sitting further back, a small source is a very bad approximation to the sound field you hear.

[sunshinedawg]

Furthermore in symphony halls most of the sound you hear is reflected, not direct, so even if you were sitting further back, a small source is a very bad approximation to the sound field you hear.

That's why you also need ambient channels to complete the soundfield.

[csero]

Can you explain that comment?

It sounds as though you're assuming that all the sound is emanating from a source that's small compared to the distance to the listener.  I guess that might be true sometimes, like for a solo instrument or singer, but usually it's not true at all (think of being in one of the front rows listening to an orchestra or jazz ensemble).

Furthermore in symphony halls most of the sound you hear is reflected, not direct, so even if you were sitting further back, a small source is a very bad approximation to the sound field you hear.

Please note, that we are speaking about 2 things, the reproduction of the first arrival of the direct sound and recreating an ambient filed similar to the original.
The direct sound is reproduced through XTC and the ambient filed  - if it is not recorded independently - created by simulation. With the proper mix of the two, you can get surprisingly "real" reproduction of real acoustic events.
Of course with studio recordings ( drums in an anechoic booth, guitars through pickup, vocal close mic-ed and with different added echo in every line ) it is a hit and miss.