Setting up the Nathan 10

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#201
The stereophonic sweet spot is very small. Maybe only one inch to the left and to the right.

Kuhl measured how big the sweet spot is in 1959. He found that it is 12 cm with a speaker distance of 2 m and 21 cm with a distance of 3 m. With omnidirectional speakers it becomes wider (14 cm for 2 m and 32 cm for 3 m) but localization of phantom sources on the sides became wrong.
He allowed for a shift of the center phantom image of +/- 50 cm. Too much for my taste. Center is center and not nearly 2 feet to the left or to the right!

So I guess Earl was talking about the area in which the frequency response to the left and the right is linear?

Best, Markus
 
#204
markus76 said:
So I guess Earl was talking about the area in which the frequency response to the left and the right is linear?
Click to expand...

not exactly, see the paper posted by Zilch above (4430).
Constant directivity is the key here.
The concept is to toe the speakers in so that their acoustic "lines" cross somewhere in front of the listener. So the listener is off axis for both speakers.
When the listener moves horizontaly, for example to the left, he is more and more on axis from the right speaker, and more and more off axis from the left speaker. This conpensate for the fact that he is moves closer to the left speaker, and thanks to constant directivity the tonal balance remains the same.
So this enlarge the sweet spot.
 
#205
speakerdoctor, Earl was referring to this post: http://www.diyaudio.com/forums/showthread.php?postid=1621526#post1621526

soongsc, have you ever experienced a bigger stereophonic sweet spot? That's simply not possible because of how stereophony works.

Here's a table what values of interchannel volume and time changes corresponds to what shift of the phantom image:
http://www.sengpielaudio.com/HoerereignisrichtungDurchPegelBzwLaufzeit.pdf
"Hörereignisrichtung" ist "direction of sound"
"Pegeldifferenz" is "difference in level"
"Laufzeitdifferenz" is "difference in time"

If you move your head out of the sweet spot you change level AND time of the signal arriving. So in the best case you get only a shift of the phantom image (in case of intensity stereophony). In the worst case you have a stereo signal that uses level AND time differences. Moving your head out of the sweet spot can lead to contradictory cues and the stereo image breaks down completely.

Best, Markus
 
#206
pos said:
The concept is to toe the speakers in so that their acoustic "lines" cross somewhere in front of the listener. So the listener is off axis for both speakers.
When the listener moves horizontaly, for example to the left, he is more and more on axis from the right speaker, and more and more off axis from the left speaker. This conpensate for the fact that he is moves closer to the left speaker, and thanks to constant directivity the tonal balance remains the same.
So this enlarge the sweet spot.
Click to expand...

Doesn't work for me. Sorry.

Best, Markus
 
#207
"not exactly, see the paper posted by Zilch above (4430).
Constant directivity is the key here."

That's not the correct system or horn. You want defined directivity you should be able to get it off the D B Keele site.


http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1983-10%20AES%20Preprint)%20-%20Horn%20Covers%20Flat%20Rectangular%20Area.pdf

JBL used these horns in Everest 1 and the 4660

http://www.lansingheritage.org/html/jbl/specs/pro-speakers/1984-4660.htm

There were later systems in the 90's with smaller versions of the horn in the 2600/3100



Rob🙂
 
#209
markus76 said:
speakerdoctor, Earl was referring to this post: http://www.diyaudio.com/forums/showthread.php?postid=1621526#post1621526


Best, Markus
Click to expand...

Thanks Markus. However I believe a preliminary assessment within the scope of a 'build' thread (post#825) is less appropriate than in the 'setting up' thread.
Only the final assessment matters here. You, the Nathans, the subs placed in your environment to your best ability with any appropriate room treatments perhaps and how you got things that way. The numbers are a somewhat interesting academic exercise, but I, and I believe others, are interested to know how you like them after listening to a variety of music for a number of hours after initial break in.

Some of the initial discussion regarding your living environment and placement of the speakers was interesting and indeed appropriate. That, unfortunately degenerated into a discussion of minutiae surrounding polar patterns, waveguides, etc... that belongs in another, more appropriate thread.

Without strick conformance to standardized test methods & conditions (environment, etc..) comparison of measurements between yourself and Dr. Geddes and any others for that matter, would seem IMHO highly questionable and problematic.
 
#210
"It is simply already toed in in the everest horn."

Hello POS

That's not entirely correct. The patern on the 2344 is symetrical in the horizontal plane. The pattern for the 4660 horn is asymetrical. You may be able to get another CD horn to mimic the patern using a combination or toe in and directivity but the 4660 type of horn is a different animal. It was specifically designed for this coverage pattern.

Rob🙂
 
#211
Markus,

Theoretically, there can be no sweep spot simply because each ear hears sound from both speakers. So really we are getting into what the trade-offs are. If we are able to have off axis response such that the intensity does not change much when we move side to side, then for most sounds it will seem that the image does not move much. Since when we move side ways, the time difference between each speaker to our ear changes pretty much in a way that should keep transient cues in the same location, then we should be able to have a large sweet spot. Looking at the Nathan curves, I would think they would give a larger sweet spot when toed in 45 deg. But if the first reflection arrive too early or too strong, then maybe the sweet spot is effected. If you are sitting back against wall less than 3M behind you, then it's probably better to have good absorption on the back wall for frequencies above 1KHz.
 
#212
markus76 said:
So I guess Earl was talking about the area in which the frequency response to the left and the right is linear?

Best, Markus
Click to expand...


Well I never have liked the term "sweet spot", but what I mean is that area where the sound image stays predominatly constant with listener position. This is about the width of the sofa in my setup.
 
#213
pos said:


not exactly, see the paper posted by Zilch above (4430).
Constant directivity is the key here.
The concept is to toe the speakers in so that their acoustic "lines" cross somewhere in front of the listener. So the listener is off axis for both speakers.
When the listener moves horizontaly, for example to the left, he is more and more on axis from the right speaker, and more and more off axis from the left speaker. This conpensate for the fact that he is moves closer to the left speaker, and thanks to constant directivity the tonal balance remains the same.
So this enlarge the sweet spot.
Click to expand...


Precisely correct and a rare instance of complete understanding of the situation. I used to do this same thing when I had 4430's.
 
#216
markus76 said:
If you move your head out of the sweet spot you change level AND time of the signal arriving. So in the best case you get only a shift of the phantom image (in case of intensity stereophony). In the worst case you have a stereo signal that uses level AND time differences. Moving your head out of the sweet spot can lead to contradictory cues and the stereo image breaks down completely.
Click to expand...

Indeed, there is but one "true" sweet spot, where both level and time cues are correct.

BUT, as the Smith et al. paper explains, the level precedence can override the time precedence within a limited range and the image will remain stable with lateral displacements of the listener. It's a psychoacoustic trick, a "Trompe l'Oreille," as it were, that works so well as to be disconcerting at first, but ultimately, is quite engaging.

Is it perfect? Well, no, and it's better with the JBL defined directivity horns Rob cites (below,) but as Pos suggests, it will work with just about any constant-directivity horn/waveguide in a system appropriately configured to generate the effect. Nothing precludes one from sitting "on center," if desired, of course.

As Earl suggests, if you're not getting it, something is wrong.... :yes:

Note: The white horns are the 4660/Everest I, not connected. What's playing is H2600/3100 on B380s
 

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#217
gedlee said:



Markus, I am shocked by this. It is probably the single most commented on aspect of my room setup that I have heard - how the image does not change reagrdless of seating location. You DON"T get this?
Click to expand...


No 🙁 Maybe the near rearwall prevents this? Distance to the base of the stereo triangle is 2.45 m. Speakers are seperated 2.28 m.

Another question: how smooth do you get the LF?

When summing left speaker, right speaker and the subs measured at the listening position I'm currently getting this:

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


Don't know what's going on at 650 Hz - could be the rearwall reflection.

Best, Markus
 
#218
Why summing? Fire them up all together. So to excite everything as it is when really listening. Your bass is based upon mutual interaction. You must let it work as a whole, so to have a realistic image. Can you hear the 650Hz thing?
 
#219
Hello Marcus

Can you post a photo from your listening position that shows how the speakers are set-up?? Might be easier to see from the photo what's going on or at least hint at why you are not getting what Earl expects you too. It does work I have used it with a couple of CD type horns and waveguides.

Rob🙂
 
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