Properties of speakers that creates a large and precise soundstage

[BenB]

I want to play a game.

Everyone take out some graph paper. Draw your listening room to scale, speakers at the top, positioned as you have yours.

Draw in their approximate radiation pattern.

Now draw the first and second reflections of those speakers as additional virtual sources on the other side of the front and side walls. Draw in the radiation patterns of the virtual mirror image speakers. What happens to the mirror image radiation patterns? Reposition your speakers. What happens to the virtual speakers?

Now formulate a theory of what causes the size and shape of the soundstage based on radiation pattern and speaker positioning.

Welcome to Image Model Theory!

This post represents a major deficiency that is common when people think about reflections and speaker-room interactions: people think in 2 dimensions and flatten the room, collapsing the vertical dimension.

In reality, the height is typically the smallest dimension, and floor and ceiling reflections (including higher order reflections such as sound bouncing first off the floor and then off the ceiling) are responsible for the vast majority of reverberant sound degradation (particularly for rooms with significant square footage). Build a speaker with a very narrow vertical beamwidth (less than 60 degrees: aka +/-30) and you find clarity much, much farther into the room than with a conventional speaker (likely all the way to the back wall).

Since the post by geickmei concentrates on soundstage, it makes some sense to prioritize the horizontal reflections, except that you have to include the virtual vertical sources to properly understand the distribution of your virtual sources even in the horizontal plane. Those vertical reflections reinforce the sound and don't widen the soundstange at all. Therefore your high-angle horizontal reflections that can widen the soundstage have to compete with more sources than the ones diagramed based on the instructions.

 

[BenB]

This already actively pursued in acoustics, but the complicated part is that the position of reflected virtual sources depend on wavelength.

The even more complicated part is modelling the perception of that mess. I don't know of any good work on this.

It may not be obvious what Curvature is referencing. For someone with flat, solid walls, the reflections will be specular for the frequencies of interest (those most related to soundstage), and this type of exercise can be insightful. But put a bookshelf on the wall at or near the reflection point, and the problem instantly becomes very complicated. Really any obstruction (curtains, chairs, diffusers, absorbers, etc or even wall materials and bracing themselves) will have a wavelength dependent (thus frequency dependent) impact on the virtual source. That's yet another dimension that needs to be considered if any accuracy is expected. If a thought experiment is all you're after, then you can ignore all that, but you should know you're ignoring it.

 

[Curvature]

This post represents a major deficiency that is common when people think about reflections and speaker-room interactions: people think in 2 dimensions and flatten the room, collapsing the vertical dimension.

In reality, the height is typically the smallest dimension, and floor and ceiling reflections (including higher order reflections such as sound bouncing first off the floor and then off the ceiling) are responsible for the vast majority of reverberant sound degradation (particularly for rooms with significant square footage). Build a speaker with a very narrow vertical beamwidth (less than 60 degrees: aka +/-30) and you find clarity much, much farther into the room than with a conventional speaker (likely all the way to the back wall).

Since the post by geickmei concentrates on soundstage, it makes some sense to prioritize the horizontal reflections, except that you have to include the virtual vertical sources to properly understand the distribution of your virtual sources even in the horizontal plane. Those vertical reflections reinforce the sound and don't widen the soundstange at all. Therefore your high-angle horizontal reflections that can widen the soundstage have to compete with more sources than the ones diagramed based on the instructions.

Humans can sense vertical position. Not very well, mind you, but we can. Research on this shows that vertical localization is inconsistent when using multiple speakers with the signal manipulated through stereophonic intensity and timing differences. One of the effects in such setups or in concert halls with hanging reflectors is vertical broadening. It is not a very significant effect, though.

I disagree with the benefits of narrow vertical directivity speakers being worthwhile. I cannot stand hearing spectral shifts as I move my head.

 

[Pearljam5000]

Which studio monitors are known to have a large and precise soundstage?

 

[geickmei]

It may not be obvious what Curvature is referencing. For someone with flat, solid walls, the reflections will be specular for the frequencies of interest (those most related to soundstage), and this type of exercise can be insightful. But put a bookshelf on the wall at or near the reflection point, and the problem instantly becomes very complicated. Really any obstruction (curtains, chairs, diffusers, absorbers, etc or even wall materials and bracing themselves) will have a wavelength dependent (thus frequency dependent) impact on the virtual source. That's yet another dimension that needs to be considered if any accuracy is expected. If a thought experiment is all you're after, then you can ignore all that, but you should know you're ignoring it.

Keep going Ben - now you are incorporating the reflecting surfaces. Do you want to put all of your equipment between the speakers at the front of the room? What does room treatment do to the imaging? There is specular, diffusion, and absorption. And if you are worried about ceiling reflections, put up some absorbers.

 

[geickmei]

Nobody has yet analyzed what happens with radiation pattern in the early reflections that causes the spatial effects that are the subject of this thread. Try drawing some "normal" speakers with a strong axial response. Their output is directed toward your ears. But where is the output of the reflected speakers going? Now reverse that pattern and direct more of the speaker's output toward the rear. What would happen with the size and shape of the soundstage?

Is it possible after all this time that most of us know all about frequency response, but nothing about spatial response?

 

[sigbergaudio]

Which studio monitors are known to have a large and precise soundstage?

Ours. Specifically the Manta, but even the SBS recently "won" when a studio evaluated it against three other well known brands. Soundstage was one of the several aspects they were perceived to be better at than the other speakers. The second best speaker were also a coaxial design, while the other two were traditional designs.

Out of respect for the other brands I'm not disclosing which ones they were, but they were all well-known brands and fairly high priced speakers.

Their testing and results are referenced here:

Sigberg Audio monitors at Kristiania University

Kristiania University of Applied Sciences selected Sigberg Audio when they needed new monitors for one of their main studios. We sit down with Claus Sohn Andersen (Head of Bachelor for Sound engineering & Music production) to learn how they ended up with Sigberg Audio, and what they think of...

www.sigbergaudio.com

Interesting/relevant quote:
"We all judged the Sigberg Audio SBS.1 system to be best or second best on every single criteria! What really set them apart for both me and others in the panel, was the soundstaging. Both in terms of width and depth, the detail in placement of various elements was exceptional. Same goes for the sense of space in the music, the Sigbergs replicated that far better than the competition."

 

[Mort]

Ours

Ok.

 

[Bjorn]

Ours. Specifically the Manta, but even the SBS recently "won" when a studio evaluated it against three other well known brands. Soundstage was one of the several aspects they were perceived to be better at than the other speakers. The second best speaker were also a coaxial design, while the other two were traditional designs.

Out of respect for the other brands I'm not disclosing which ones they were, but they were all well-known brands and fairly high priced speakers.

Their testing and results are referenced here:

Sigberg Audio monitors at Kristiania University

Kristiania University of Applied Sciences selected Sigberg Audio when they needed new monitors for one of their main studios. We sit down with Claus Sohn Andersen (Head of Bachelor for Sound engineering & Music production) to learn how they ended up with Sigberg Audio, and what they think of...

www.sigbergaudio.com

Interesting/relevant quote:
"We all judged the Sigberg Audio SBS.1 system to be best or second best on every single criteria! What really set them apart for both me and others in the panel, was the soundstaging. Both in terms of width and depth, the detail in placement of various elements was exceptional. Same goes for the sense of space in the music, the Sigbergs replicated that far better than the competition."

Since you didn't want to compare Saranna in a review against the Vera Audio Coherence 12, perhaps you are willing to allow a comparison review with several listeners with the Manta against the Coherence 12?
After all, you have already linked to a comparison review in favor of your speaker.

Large and precise soundstage is one the qualitites that can be tested by the listeners.

 

[sigbergaudio]

Since you didn't want to compare Sarana in a review against the Vera Audio Coherence 12, perhaps you are willing to allow a comparison review with several listeners with the Manta against the Coherence 12?
After all, you have already linked to a comparison review in favor of your speaker.

I have already explained to you why this is not worth my time. This comparison review was carried out by a customer, not by me. I wasn't even there. If anyone are interested in doing this, they are of course free to do so.

 

[sigbergaudio]

Ok.

Hehe, my apologies if that came out wrong - but I was after all the one who started this thread originally, and one of the reasons was because this is a property often commended in our designs - so I think it's an interesting aspect / property. I am very open to the fact that there can be multiple approaches to achieving this, but our designs are arguably at least one approach that appears to be working quite well.

 

[geickmei]

Hehe, my apologies if that came out wrong - but I was after all the one who started this thread originally, and one of the reasons was because this is a property often commended in our designs - so I think it's an interesting aspect / property. I am very open to the fact that there can be multiple approaches to achieving this, but our designs are arguably at least one approach that appears to be working quite well.

Well then Sig you should be able to tell us what it is about your designs that causes the huge, deep, wide, expansive soundstage. It looks like an ordinary box speaker, with all of the drivers on the front. Further, you say in the writeup that we should place them against the wall. That just doesn't sound right to me. Splain...

 

[sigbergaudio]

Ok.

And since I see that both you and @Pearljam5000 are Genelec fans, I can disclose that Genelec was not part of the test. There are many Genelecs that measure quite similarly to the SBS.1, and they also have similar design ideas. But we currently don't really know to what extent similar CEA2034 results also imply similar performance with regards to soundstage.

 

[sigbergaudio]

Well then Sig you should be able to tell us what it is about your designs that causes the huge, deep, wide, expansive soundstage. It looks like an ordinary box speaker, with all of the drivers on the front. Further, you say in the writeup that we should place them against the wall. That just doesn't sound right to me. Splain...

If we go way back to page 1, we can find some of them in my initial post.

• Perceived point source / coaxial design.
• Even off-axis response / controlled directivity.
• Linear phase crossover between tweeter and midrange
• Correct tonality / enough energy in the bass (20-500hz)

 

[Mort]

And since I see that both you and @Pearljam5000 are Genelec fans, I can disclose that Genelec was not part of the test. There are many Genelecs that measure quite similarly to the SBS.1, and they also have similar design ideas. But we currently don't really know to what extent similar CEA2034 results also imply similar performance with regards to soundstage.

I also have a wide directivity ribbon tweeter from Philharmonic Audio. About 75 probably. It's gloriously wide but not that precise.

Yeah the Genelecs are narrower and primarily used for nearfield with low late reflection. They are thrillingly clear and precise but the image doesn't extend much beyond the speaker.

The 8361a is particularly enveloping, possibly because of the mid bass adequacy you suggest is needed.

 

[sigbergaudio]

I also have a wide directivity ribbon tweeter from Philharmonic Audio. About 75 probably. It's gloriously wide but not that precise.

Yeah the Genelecs are narrower and primarily used for nearfield with low late reflection. They are thrillingly clear and precise but the image doesn't extend much beyond the speaker.

The 8361a is particularly enveloping, possibly because of the mid bass adequacy you suggest is needed.

Right. Here's the 8361A vs SBS.1 (bass missing in the measurements from the SBS.1 since it's using separate subs to reproduce that).

CEA2034 relatively similar:

Estimated in-room quite similar (SBS has more energy in the midbass):

But some clear differences in for instance horizontal polar:

 

[Mort]

From your horizontal plot, it looks like the 'center' is more narrow but the off axis trails off more slowly emphasizing reflections a bit more than the Genelecs.

For my music (pop, rock, metal) I prefer to keep the reflections low. When I listen to acoustic, I enjoy the wider ribbon tweeter.

 

[thewas]

But some clear differences in for instance horizontal polar:

Also the directivities are quite different with the 8361 being more kind of CD and yours continuously increasing which both have different fans here.

 

[geickmei]

Right. Here's the 8361A vs SBS.1 (bass missing in the measurements from the SBS.1 since it's using separate subs to reproduce that).

CEA2034 relatively similar:

View attachment 456552

Estimated in-room quite similar (SBS has more energy in the midbass):
View attachment 456554

But some clear differences in for instance horizontal polar:

View attachment 456553

Again with the frequency response curves. Frequency response has nothing to do with spatial response.

Again with the highly directional polar response. That response would have no spatial qualities. Speakers would call attention to themselves and not disappear.

 

[sigbergaudio]

Also the directivities are quite different with the 8361 being more kind of CD and yours continuously increasing which both have different fans here.

View attachment 456555

And here is 8361 vs Manta for reference/comparison: