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The most important factor in soundstage imaging

Everybody wants a system that images well. There are  many discussions here positing equipment changes that will improve imaging. Some people think the magic wand is cables, others are sure it’s the preamp, and the ones that don’t think it’s preamps, think it’s amplifiers. And, of course, speakers are (correctly) mentioned. 

However, the single most important factor in audio stereo imaging, is increasing direct radiation and decreasing reflected radiation, by moving the speakers away from the back wall, and away from the side walls. 
128x128phomchick
mijostyn's avatar
mijostyn
8,221 posts
 
Hi phomchick,
It is a wonderful experience to listen to a system that has a holographic image. You are right. Reflected sound particularly the early louder reflections can wreak havoc particularly with point source radiators. This is the largest advantage in using a dipole. Dipoles radiate in a figure 8 pattern with very little radiation to the side. If they are set up as linear arrays then they do not radiate up or down either! There is only one early reflection right behind the speaker. All you need to do is glue some foam acoustic tiles to the wall behind the speaker and you are all set. 
There are other factors that when handled appropriately improve imaging quite a bit. These are phasing, all drivers have to be adjusted so the sound of each driver subs included, arrive at the listeners ear at exactly the same time. The main left and right channels have to have the exact same frequency response curve. The curve does not have to be flat but the channels have to be exactly the same at all frequencies. The only way to achieve this is in the digital domain with dare I say it, room control.
Room control is improving in leaps and bounds. The best I have heard is the Trinnov system. Second is Lyngdorf's system. I'm going to catch it now but a tube phono amp sent through a good ADC (Benchmark!) then through room control will image better. Way better. Magically better. 
OK I'm ducking:-)
mrdecibel
2,925 posts
 
I appreciate the op’s post, and agree with the importance of his assessment, but ime, there are many more factors in getting excellent staging and imaging.
helomech
1,519 posts
 
Moving them away from the walls usually goes a long way toward improving imaging, especially soundstage depth.
audiokinesis
2,720 posts
 

Phomchick wrote: "The single most important factor in audio stereo imaging, is increasing direct radiation and decreasing reflected radiation, by moving the speakers away from the back wall, and away from the side walls."

I would agree that minimizing early reflections is AMONG the most important factors, but I don’t know what is THE most important factor.

Warning: The following is fairly technical, please skip it if you prefer not to read technical explanations.

Very early reflections (within about .68 milliseconds of the direct sound) are arguably the most detrimental to imaging, as they occur before the Precedence Effect kicks in. (Sound travels about 9 inches in .68 milliseconds). These are usually reflections (or diffractions) associated with the front baffle and sometimes associated with the drivers themselves. This brief time interval is within the arrival time difference for off-centerline sounds that arrive first at one ear and then at the other, from which we compute the angle that the sound comes from, which is why they tend to be especially detrimental to precise imaging. The longer the time interval (up to .68 milliseconds) before a sound arrives at the farther ear, the further off-centerline the sound seems to come from. So as we get closer to the .68 millisecond threshold, a correspondingly further-around-to-the-side false localization cue is generated. I believe this is why narrow speakers generally (there are many exceptions) image better than wide ones: Because the cabinet edge diffraction happens earlier within that .68 millisecond window.

Next we have the early reflections off of room boundaries, and the sidewall reflections are probably the most significant. They tend to "broaden" the image size, which many people find subjectively pleasing (according to Toole), but they can also degrade clarity (according to Geddes and Griesinger). These early sidewall reflections also tend to reduce the soundstage depth. Along with the (subjectively more benign) floor and ceiling bounces, the early sidewall reflections tend to superimpose a "small room signature" on the sound, which tends to mask the soundstage on the recording.

Ime relatively late-onset (after about 10 milliseconds) reflections are generally not detrimental to image localization, and can be beneficial by increasing the sense of envelopment and immersion within the soundscape on the recording. I like to intentionally increase the amount of late-onset reverberant energy for this reason: The ear/brain system judges the room size by the time interval between the first-arrival sound and the "center of gravity" of the reflections. By pushing that "center of gravity" further back in time, we reduce the amount of "small room signature" that is super-imposed atop the soundstage on the recording. Incidentally this is what acousticians try to do when designing the control room for a recording studio, so that the engineers can clearly hear the soundstage on the recording without the control room’s signature being super-imposed on top of it.

Imo, ime, ymmv, fwiw, etc.

Duke

james63
534 posts
 
Well this thread is done, Duke summed it up lol. 

So what about electronics? Why does one solid state amp have a larger sound stage than another solid state amp?
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