3D imaging

What makes speakers produce a 3D image is being symmetrically equidistant and pointed towards the listener. Period.

While precisely balanced speakers are important, not all speakers sound at their best this way. 

Quite frankly, some speakers sound better off-axis. A lot of high quality tweeters have resonances which you can tame by toeing the speakers out.  Further, if you have a very small room, sometimes crossing the speakers in front of your head reduces side reflections significantly and improves imaging.

Lastly, as some speaker developers have discovered, despite our best intentions, sometimes listening below the tweeter axis is also beneficial.

The final judge is your ears and your circumstances.


Best,
E

This is all fascinating stuff. Of course some of what I'm reading about HRTF is way above my head,pun intended. I had absolutely no idea that the size,and shape of your head,and torso play a role in what we hear. That explains a lot about what sounds pleasing to me,may sound like nails against a chalkboard to you. The plot thickens............

Thanks for the input millercarbon. I rotate 3 sets of speakers in my system,(Hornshoppe Great Horned Heils,Nola Boxer 2's,and Graham Chartwell LS3/5's). They all throw a great 3D image,so I guess I'm doing something right. I was just curious if the speaker design was responsible.

 I've read posts on other forums where posters think that attaining 3D imaging is just chasing unicorns. Obviously they are doing something wrong.
   
  As a side note,I've been at this hobby for a bit,and I'm no spring chicken. I just don't have a ton of technical knowledge. This is one reason I frequent this site. There are a large number of members here that DO have a vast knowledge of things audio. I find that exposing myself more to the technical aspect of this hobby will help me understand what I am hearing to a greater degree.
    Again,thanks for your response,
           Ray

Okay. Thanks. Got it. First stab answered your literal question. Now with more info I can give a much better answer.

Almost all our sense of location comes from the midrange on up, and is based primarily on arrival times. That's why location is so important, and makes a difference to the point even as little as 1/8" can be noticeable.

 I was just curious if the speaker design was responsible.

It is. Sound waves coming off a driver radiate out in an arc. Because of the way waves travel they reflect (bounce) or diffract (scatter) or refract (bend) off anything they hit. 

Now this is a Big Deal for speaker designers, because it turns out sounds that arrive within a window of about 3 to 5 milliseconds of each other tend to be perceived as coming from the same source. 

So let's say you have a midrange driver mounted in a great big speaker with an edge around the speaker like for a dust cover. Sound coming off the driver radiates out and all along the way is reflecting off the baffle, and then reflects and refracts again at the edge. 

Physics: sound travels roughly 1 foot per millisecond. So all the reflections and refractions are well within this critical window.

Now you know why so many drivers are mounted flush, in super smooth baffles, with nothing sticking out, and often with felt or other material to absorb these reflections, and all in a cabinet no bigger than it absolutely has to be. 

There's also the speaker cabinet itself. Its hard to notice because so much of the sound comes from the drivers, but play something loud and feel the sides of the cabinet, especially the front. If that is moving at all then its radiating sound. So now you know why so many really good speakers are massive and have super strong cabinets. If the cab vibrates at all it is in effect another speaker blurring arrival times and ruining imaging. This is really, really hard to do, especially as you get bigger and bigger, and goes a long way to explaining why so many small speakers are sound staging champs.

Then there is the fact that just as much sound radiates off the back of the driver and into the cab as out into the room. Very big problem. Unless its highly damped this sound will reflect off the back of the speaker and come right back out through the driver. Only delayed. Another hit to imaging. So even internal construction and damping matters.

Now if you caught the 3-5 ms rule then you also learned why it helps imaging to have speakers placed 3-5 feet away from walls. 

You ask for vast knowledge of things audio, you get vast knowledge of things audio. What else you wanna know?

Excellent explanation. That explains why my choices in speakers seem to work so well in my small listening room.(9x13x8) This room has only one purpose,so I have no restraints as far as set up goes. Obviously with a small room,I have to make certain compromises,but I think I have done a pretty reasonable job of speaker choice and placement. My biggest compromise is distance from side walls, not much I can do about that,however I do have treatments at the first reflection points,which helps. I guess my next question will be a little more involved. How do downstream electronics help or hinder 3D imaging?

Rocray -

Of course, to preserve the location data you need good room acoustics. I strongly recommend GIK accoustics. Great advice and very cost effective products.