How far should speakers be placed away from walls to eliminate smearing from early reflections?

May 30, 2010
15,506
715
113
Portugal
#21
Hi Microstrip,

Thanks. Can you please elaborate a bit on "some proper reflection" vs. smearing from too much reflection?
You are just asking the critical question. The more elucidating information is this aspect I have found comes from the Stanley Linkwitz site http://www.linkwitzlab.com. Surely it is his own view on the subject - it interested me a lot as I owned (and still own ...) big dipoles. Some people strongly disagree with him on the role of reflections in stereo. On this subject he writes " Each loudspeaker also must be placed at some distance from front and side walls so that reflections reach the ears later than the direct loudspeaker sounds. In that case the brain can filter out the direct sound streams more readily from those due to reflection and reverberation. A minimum time gap of 6 ms between direct and reflected sounds is needed, which translates to a minimum distance of 1 m from the walls. "

Please read point 3.1 Loudspeaker placement of the page of http://www.linkwitzlab.com/Recording/AS_creation.htm
 

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caesar

Well-Known Member
May 31, 2010
3,188
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#22
Gentlemen, thank you for the great discussion.

What is the reason that we do not see more placements of speakers on the long wall? Does that, generally, put the listener's head too close to the back wall? Or are other problems created that way?
 

DaveC

Industry Expert
Nov 16, 2014
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#23
Gentlemen, thank you for the great discussion.

What is the reason that we do not see more placements of speakers on the long wall? Does that, generally, put the listener's head too close to the back wall? Or are other problems created that way?
Sometimes, and that's a big problem. The listening position needs to be away from the back wall for best results as well.
 

DaveC

Industry Expert
Nov 16, 2014
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#24
You are just asking the critical question. The more elucidating information is this aspect I have found comes from the Stanley Linkwitz site http://www.linkwitzlab.com. Surely it is his own view on the subject - it interested me a lot as I owned (and still own ...) big dipoles. Some people strongly disagree with him on the role of reflections in stereo. On this subject he writes " Each loudspeaker also must be placed at some distance from front and side walls so that reflections reach the ears later than the direct loudspeaker sounds. In that case the brain can filter out the direct sound streams more readily from those due to reflection and reverberation. A minimum time gap of 6 ms between direct and reflected sounds is needed, which translates to a minimum distance of 1 m from the walls. "
Is that your experience too? I feel like 1 meter is pushing it and 1.5+ is better.
 
May 30, 2010
15,506
715
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Portugal
#25
Is that your experience too? I feel like 1 meter is pushing it and 1.5+ is better.
Impossible in my room - in the first reflection zone the room is 15 feet wide - the speakers are 2 feet away from the wall. The Soundlab's were even closer.
 

RogerD

Well-Known Member
May 23, 2010
3,482
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63
BiggestLittleCity
#26
My speakers have always given the best results when they are in front of the back wall by 7ft and inboard by 3.0ft. I try and keep my listening chair about 11ft from the speakers. I have always had a room that opens into a much larger space. Now I don't know if the incomplete walled room acts as a Helmholtz resonator or not,but I feel that, that kind of opening has always produced the best sound.
 
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ack

VIP/Donor & WBF Founding Member
May 6, 2010
5,637
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Boston, MA
#27
It depends on the dispersion pattern of the speaker, size of room and personal preference. My preference would be a somewhat nearfield setup with the speakers a good distance from any of the walls and a controlled, even and smooth dispersion pattern.
Agreed that's how I am set up
 

DaveC

Industry Expert
Nov 16, 2014
2,598
494
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#28
Impossible in my room - in the first reflection zone the room is 15 feet wide - the speakers are 2 feet away from the wall. The Soundlab's were even closer.
From the side walls? That's not as critical with dipoles due to the cancellation effects but distance from the front wall matters more imo... I used to have Mirage Bipoles many years ago. :)
 

JackD201

[WBF Founding Member]
Apr 21, 2010
11,353
296
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Manila, Philippines
#29
For small rooms 100 ms isn't practical as that takes about 33 meters. General rule of thumb is ~4 meters so speakers should ideally be 2 meters or more from sources of reflections.
Difference of around 6 ft with treatment is about right. 100 ms is the untreated ideal that's why you need to use one of the 3. Absorption lowers amplitude, diffusion randomizes, redirection lengthens the path away from the listener as in using splays but to deal with reverberation one will need to treat the 2nd or even the 3rd boundary.
 

JackD201

[WBF Founding Member]
Apr 21, 2010
11,353
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Manila, Philippines
#30
Most SMT products I see are diffusors.
 
Feb 8, 2011
21,948
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113
Vancouver Island, B.C. Canada
#31
What is the ideal distance for speakers to be placed away from walls to eliminate the smearing effect of early reflections?

In a perfect scenario, is the middle of the room the best place?

Thank you
As a general rule; one third of the room's length, and one fifth of the room's width.
There are also other rules, like the lower woofer not the same distance from the floor and from the side wall, or multiples (2x, 3x).
If the side walls are treated, the amount of toe-in is less dependent.
http://www.soundfountain.com/amb/speaker.html
http://www.westlakeaudio.com/Speakers/Manuals/body_positioning_loudspeakers_in_th.html

* The middle of the room is NOT the best place.

http://www.audiophysic.com/aufstellung/regeln_e.html
http://noaudiophile.com/speakercalc/
http://www.tweakshop.com/Speaker Placement.html
 
Feb 8, 2011
21,948
606
113
Vancouver Island, B.C. Canada
#32
Anyways, is there an ideal distance away from the walls for one not having to deal with this problem?
http://www.tweakshop.com/Speaker Placement.html

1. Room length:
If your room is a rectangle, the speakers will ideally face the length of the room, so place your desk by the shortest wall.

2.Think in thirds:
Imagine dividing the length of your room by three. Your speakers will sit within the first third of the room and more than 1m from the side walls. We did say you needed some room...

3. Speaker angles:
Music is generally released in stereo, which means the sound is spread between the left and right speakers. Positioning the speakers at a 60-degree angle gives you the best 'stereo image' of these sounds. Dust off your old protractor and position the speakers 60 degrees apart. It can help to place a small marker at your listening position and work it out from there.

4. Space from wall:
If you really do have a huge room to work with, pull the speakers away from the wall. There's a zone between 1m and 2.2m that ideally you want to avoid. If you have a smaller room, try to leave as much space as you can between the wall and the speaker -- up to 1m -- and do not place them too close to the wall either as the bass doesn't play well.
 
Feb 8, 2011
21,948
606
113
Vancouver Island, B.C. Canada
#33
Gentlemen, thank you for the great discussion.

What is the reason that we do not see more placements of speakers on the long wall? Does that, generally, put the listener's head too close to the back wall? Or are other problems created that way?
For average room's size (European* and North American) the long walls are generally prefered, for room breathing between the loudspeakers and the listener.
But some people have no choice, or prefer large distance between the two speakers (wide soundstage).
And if the room is 22 feet long by 19 feet wide, it is quite flexible...or on the long or on the narrower wall.

* In Europe, generally they have smaller rooms.

** Post #21 (by micro) is excellent.

*** I like speakers that have a smooth on and of axis dispersion response. ...Tight together following a directional pattern on the same wavelength.
...Say from zero to 60°
 

audioguy

WBF Founding Member
Apr 21, 2010
2,765
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Near Atlanta, GA but not too near!
#34
My speakers are about 4.5 feet from side walls. I have had them closer in other rooms. Side wall first reflection diffussion, in my experience, makes the distance issue not too critical. Very easy to measure ... and hear. I use absorption for 2nd reflection point (opposite wall speaker). And like most of high end audio, personal preference still rules the day.
 

Mark Seaton

WBF Technical Expert (Speaker & Acoustics)
May 21, 2010
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Chicago, IL
www.seatonsound.net
#35
I missed this thread previously, but thought I'd link to a nice summary Nyal Mellor has posted the matter here titled "Early Reflections 101."

The key understanding is that both level and timing of a reflection matters. This explains why certain locations work just fine with one speaker, say a dipole/open baffle design, but less so with another. The relative level an spectral balance of the off axis energy can be very different between different speakers, hence reflections can come back at significantly different levels.

While the article has many good points, here's an old graphic posted in it which should be digested a bit:
 
Dec 13, 2010
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#36
Some comments:

What is the ideal distance for speakers to be placed away from walls to eliminate the smearing effect of early reflections?
Smearing would imply that there is some kind of deterioration of timbre and/or image/sound stage. To the best of my knowledge the scientific literature does not provide the slightest shred of evidence that there is deterioration when playing music through 2-channel stereo systems in real rooms with multiple reflections and reverberation. If such negative effects occurred they would also occur with natural sound sources such as one’s wife/kids/dog/cat. Do they?


Look up the Haas effect. There is a window where early reflections are BAD because in this short time range the brain mixes the direct and reflected sound. Outside of that the brain can distinguish direct from reflected and this is what is subject to preference.
To begin with, Haas performed his experiments in open air, and used a single speaker as direct sound source and a single speaker for the lateral reflection, with each speaker at an angle of 45 degrees w.r.t the listening axis, and he further used speech. He found that within a window of 1-30 ms a broadening of the direct sound source was perceived, with the sound having more body, which was considered as positive by the listeners. A critical delay was defined as the delay where 50% of the listeners considered the reflection as disturbing, the average value being 44 ms. At a delay of 100 ms 100% of the listeners considered the reflection as disturbing.

The delay at which the reflection is perceived as echo is called echo threshold. Its value depends on the type of signal and is between 5ms (clicks) and 80 ms (slow music).
If the arrival times, like you suggest, are outside of the “problematic“ time window, you’re outside the window within which the precedence effect operates and will perceive reflections as echoes.


While the article has many good points, here's an old graphic posted in it which should be digested a bit:
This graph is equivalent to fig. 6.5 of Toole’s book, where the accompanying text says: “An illustration of the several audible effects that occur when a single lateral reflection is added to a direct sound, in an anechoic simulation similar to that shown in fig. 6.4b. All of these curves were determined using speech a signal “

In all of these experiments a single speaker was used as direct sound source. No such data exist for 2-channel stereo in real conditions with multiple reflections+reverberation and music.

Klaus
 

sbo6

Active Member
May 19, 2014
817
49
28
Round Rock, TX
#37
Harman's research says sidewall reflections are desirable and give you a sense of spaciousness.
I would agree. While you can get good results with absorption on sidewalls you won't know what you're missing unless you try diffusion, room dimensions permitting. Also, there is no perfect RT60.
 

sbo6

Active Member
May 19, 2014
817
49
28
Round Rock, TX
#38
What is the ideal distance for speakers to be placed away from walls to eliminate the smearing effect of early reflections?

In a perfect scenario, is the middle of the room the best place?

Thank you
The cardas room setup guide is a good starting point which for cones = RW * .276 from woofer to sidewall and RW *.446 woofer to front wall (behind speaker).

http://www.cardas.com/room_setup_main.php
 

Mark Seaton

WBF Technical Expert (Speaker & Acoustics)
May 21, 2010
332
25
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43
Chicago, IL
www.seatonsound.net
#39
I would agree. While you can get good results with absorption on sidewalls you won't know what you're missing unless you try diffusion, room dimensions permitting. Also, there is no perfect RT60.
Especially since RT60 doesn't really exist, nor have much application in domestic listening rooms. In general it only comes up when using rule of thumb calculations for % surface area coverage which again don't have much application in our listening spaces.
 

JackD201

[WBF Founding Member]
Apr 21, 2010
11,353
296
83
Manila, Philippines
#40
Especially since RT60 doesn't really exist, nor have much application in domestic listening rooms. In general it only comes up when using rule of thumb calculations for % surface area coverage which again don't have much application in our listening spaces.
I suppose that is more true of typical USA construction which uses a lot of gypsum, rock wall and have insulated gaps to boot. It's much more of a factor in places where codes require load bearing walls of poured concrete or older homes with heavy masonry. we end up building walls like yours on top of our own.

My room is far from typical. I wish it was to be honest. The only place I could build a room big enough was to dig down. After a retaining wall sprung a leak during a long and heavy monsoon, I stripped off all the false walls and redid the walls and floors with shotcrete over space frame. Oh Lord. I remember being in the room inspecting the bare walls and floor when one of the workers came in and plopped down a full bucket of sealant. The thud went on and on. That was with the untouched ceiling where incidentally my bass traps are mounted. I could help but wonder how bad the decay times would be if even the concrete ceiling which is close to 80 square meters was bare.
 

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