Can speakers positioned very close to the wall produce a good soundstage?

Nyal Mellor · Aug 15, 2011

What is it about pulling speakers 4ft out into the room that increases perceived spaciousness and depth? Why is it that when speakers are very close to a wall they almost always seem flat and 2 dimensional?

Does anyone have any good theories or psychoacoustic explanation?

DonH50 · Aug 15, 2011

Early reflections and comb filtering is a good start... If the reflections come too soon (i.e. too close together) your ear/brain does not separate them, and you lose some of that sense of space. Three feet adds about 6 ms of delay (six feet total extra travel), enough that we start to notice.

IMO - Don

JackD201 · Aug 15, 2011

I've heard many soffit mounted systems that imaged very well. Also some free space loudspeakers. These speakers were designed to be used that way though (Duettes, Unifield 3s). My guess is the LF contour.

NorthStar · Aug 15, 2011

Most loudspeakers are build to sound best from at least a reasonable distance from the front and side walls.

* Take a person (female) for example (a singer); she sounds much better standing free of any boundaries than close to the walls.
Same for a piano.

Does that make good sense?

________________________

And same for a listener; you don't listen from close to a wall right?
The best seats in a Concert Hall are always from the 'F' to 'J' rows.
'H' row is great!

'I' too.

Bruce B · Aug 15, 2011

When Bob Hodas tuned our room and positioned our speakers, he said the best measured performance was up against the wall. Good thing it has front firing ports.

NorthStar · Aug 15, 2011

Off-axis sound propagation, and room boundaries, create delayed reflections in a normal room, that can impede with the direct sound.

...And affecting proper Imaging.

rblnr · Aug 16, 2011

What is it about pulling speakers 4ft out into the room that increases perceived spaciousness and depth? Why is it that when speakers are very close to a wall they almost always seem flat and 2 dimensional?

I think what Don says is true, and with certain speakers/rooms I've certainly noticed an increase in soundstage depth when I put absorption on the wall between the speakers. But it's also that our ears aren't separate from our eyes -- we see speakers flat against a wall, there's no room for depth between and behind the speakers. Our eyes/brain tell us this.

Some years ago I reviewed Guru QM10 monitors -- small speakers designed for against wall placement, and they recommended some absorption on the wall just to the inside the speaker. These were designed by a guy who had a doctorate in human hearing. The absorption helped, but another part of the way they got around the conundrum a bit was they had exceptional image height for their size (and amazing bass too). You saw this huge image in front of you - the size of which fooled you into perceiving depth. Not explaining the phenomenon particularly well here, but the design worked. The xover was unusual in that it put a small part of the frequency band that went to the tweeter thru the mid/woof as well.

I find controlled directivity speakers do a pretty good job of imaging depth with against wall placement too. I have a pair of Amphion Ions in this setup. CD speakers like Amphions tend to image out in front of the speaker plane, so there's 'room' for depth behind.

I'll be getting a spiritual successor of the QM10s soon 'The Clue' by sjofnhifi.com that claim to perform the same trick.

MylesBAstor · Aug 16, 2011

Nyal Mellor said:
What is it about pulling speakers 4ft out into the room that increases perceived spaciousness and depth? Why is it that when speakers are very close to a wall they almost always seem flat and 2 dimensional?

Does anyone have any good theories or psychoacoustic explanation?

I haven't always found that to be the case. Depends upon the speaker design. One of my colleagues had Infinity RS1bs (reworked of course) with the midrange panels placed out say 6 or so ft into the room (roughly 25 or so by about 14 ft) and the woofer towers in the corners of the room. Inches made all the difference in the integration of the panels/woofers, esp. in the upper bass through lower mids. But the midrange panels were only say a foot or so from the side wall and he had a glorious soundstage. In fact, he had one of the best sounding systems I've ever heard.

naturephoto1 · Aug 16, 2011

Though they are not right against the wall, I have my OMA New Yorker horn speaker cabinets (compression horn drivers about 8" forward from the rear of the cabinets) toed in and about 16" from the inner side and about 23" from the outer side from the front walls of the room. The speakers are also about 4' from the side walls and I have 2 2' X 4' 3 1/2" (2" panels with an additional space of 1 1/2") deep absorbing panels behind each speaker and 2 pair of Tri-Traps stacked in the corners of the room. It is possible that they would sound better further from the front walls, but the speakers had to be placed on the 19' 4" L wall; the room depth is 14' 7" and has a 9' ceiling. I am still working to install additional room treatments, but the speakers image quite well with a wide and deep soundstage definitely appearing to be substantially larger than the room itself.

Rich

Nyal Mellor · Aug 16, 2011

My thoughts so far based on your input:

- flush mounted speakers will not have a 'back wall reflection'
- conventional monopole speakers, where these effects are typically quite obvious, if positioned close to wall and toed in normally would have a reflection from the wall between the speakers
- the further speakers are pulled out from the wall this reflection becomes less strong since the the sound energy drops over over distance and also with speakers being directional at mid and high frequencies the reflection from the wall becomes increasingly dominated by low frequencies which radiate more omnidirectionally. The same effect would also be achieved through absorption between the speakers
- CD and dipoles obviously have very different interactions with the wall behind the speakers. Linkwitz published an interesting thought piece on 'The Wall Effect' which is good reading and very relevant to this discussion http://www.linkwitzlab.com/orion++.htm

I agree that LF contouring is also a major contributing factor to clarity and balance but I'm how it impacts imaging and soundstaging per se.

So maybe it is closely related to the level and time delay of the reflection from the wall behind the speakers.

NorthStar · Aug 16, 2011

Nyal Mellor said:
My thoughts so far based on your input:

- flush mounted speakers will not have a 'back wall reflection'
- conventional monopole speakers, where these effects are typically quite obvious, if positioned close to wall and toed in normally would have a reflection from the wall between the speakers
- the further speakers are pulled out from the wall this reflection becomes less strong since the the sound energy drops over over distance and also with speakers being directional at mid and high frequencies the reflection from the wall becomes increasingly dominated by low frequencies which radiate more omnidirectionally. The same effect would also be achieved through absorption between the speakers
- CD and dipoles obviously have very different interactions with the wall behind the speakers. Linkwitz published an interesting thought piece on 'The Wall Effect' which is good reading and very relevant to this discussion http://www.linkwitzlab.com/orion++.htm

I agree that LF contouring is also a major contributing factor to clarity and balance but I'm how it impacts imaging and soundstaging per se.

So maybe it is closely related to the level and time delay of the reflection from the wall behind the speakers.

Surely is!

Tom Danley · Aug 16, 2011

Hi Nyal
AS others have suggested close reflections that a nearby wall can produce have a negative effect on stereo imaging. These reflections are caused by sound which radiates sideways and he problem is controlling this radiation requires physical size at a minimum and a design which resolves that problem on top of it. The alternative is lots of side wall absorption and moving the speakers away from the walls.
The problem is akin to what is required to make two speakers operate side by side and NOT produce an audible seam or comb filtering as the physical boundary of a wall is very similar to the acoustic mirror effect of an adjacent speaker.
At work, we make speakers for commercial use where fidelity is important, some of these can be placed hard against the wall or other boundary and not produce any reflections or comb filtering. The measure response at the listening position is also preserved much more intact. To accomplish that one needs to have very good control of the polar pattern. While it is not common in hifi yet, it is pretty much the norm to measure a speaker over a full sphere to ascertain the entire radiation.
Best,
Tom Danley
Danley Sound Labs
http://www.facebook.com/DanleySoundLabs?ref=ts
http://www.danleysoundlabs.com/

Grainger49 · Oct 25, 2011

My experience has been that the speakers I have owned didn't throw a decent soundstage until they were feet away from the back wall. The problem is that each speaker system is different. The early Allison speakers were intended to be placed against the back wall.

My advice is try both positions and see which is most pleasing to you. Then learn to live with it if it is inconvenient, or just lug the speakers out when listening.

NorthStar · Oct 25, 2011

It's a balancing act. ...Between loudspeaker on & off-axis dispersion and wall & ceiling first reflections. ...And listening position.

* Tom, above, mentioned another related very good point:
Polar Dispersion Response Pattern (360 degree). ...In the Vertical and Horizontal planes.

3D?

...You bet!

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Can speakers positioned very close to the wall produce a good soundstage?

Nyal Mellor

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