This is a guide to help those who have the space so they may place their stereo speakers in such a manner as to enable them to get everything out of the recordings they have. The purpose is to place the speakers in such a way that standing waves will not cause interference and cause “dead” ranges of the audio spectrum as well as trying to prevent accentuating those frequencies which would only serve to diminish the listening experience by overshadowing other frequency ranges. It won't help with those portions of the sound spectrum that are inherently weak in many systems, but it will help prevent deviation from what is on the original recording. That's what the musicians want you to hear and it can be assumed that you do as well. What we are aiming for is as flat a spectrum as possible enabling the entire recording to be heard well.
I would like to thank beforehand the nice folks at Cardas Inc. for their permission to use their graphics of speaker placement and the detailed information which has been a great help in putting this guide together.
I would like to also thank our own TNTTNT for his insight and mathematical formula for figuring out where potential interference will probably occur for any given environment as well as his graph showing his own measurment for his own system in his listening area at home.
There are a few different methods for placement which will be detailed here: the 1/3 and 1/5 rules, the Cardas method and the Allen Perkins method. Near field listening placement will be taken up in another guide.
I will also delve into dealing with furniture and it's ability to affect the sound dispersion in your listening room but I will not do into great detail about that here. That is for a sticky on room treatment.
It must be stated that when initially placing your speakers you should place them so there is no toe-in until you have ascertained that they are in the placement that gives the best audio response. This may take days or even weeks or moths of tweaking. Patience is key, but the reward is getting the best sound out of your system that you can.
1) There are two rules for speaker placement which I will go into first, the 1/3 rule and the 1/5 rule. These rules state that after room measurements have been made the speakers will be placed either 1/3 or 1/5 of the distance from the back wall into the listening room. This will help mitigate standing (interference) waves which will cause dead portions of the audio spectrum to be a problem. There is also a school of thought that the speakers will be placed at 1/3 or 1/5 of the distance from the side walls at the same time. I must emphasise that it is the radiating cone or dome of the tweeter that is placed in the exact spot indicated by measurements.
If you have a room that is 20 feet (6m 10cm) long then the speakers would be placed 80 inches from the rear and side walls for the 1/3 method and 48 inches for the 1/5 method. Whichever method you use should also apply to placement of your listening platform (chair or sofa). In other words, if you have your speakers 1/3 of the way from the rear wall, your sofa should be 1/3 of the way from the wall behind the sofa. The same ratio applies to the 1/5 rule. Remember to place your listening seat evenly between the speakers. Also, measure where your ears actually are when you listen so they will be placed at the 1/3 or 1/5 junction, not just near it. You may need someone else to help you with this since they can actually measure distances as you sit in a comfortable listening position. Adjustments can then be made accordingly. Part of what you are trying to accomplish is the partial diminishing of reflections from the side, rear and behind the listening seat walls as well as from the ceiling. You don't want the music to come primarily from the perimeter but from the center of the sound stage radiating outward.
2) The Cardas method states that there are mathematical formulae which can be used to mitigate standing waves and promote a natural sounding soundstage emanating from your speakers. Simply put the speakers should be placed 44.7% of the distance of the total length of the room from the rear wall and 27.6% of the distance from the side walls. It should be noted that this ratio is intended for the woofers, not the tweeters. If your room is 20 feet long and 15 feet wide your speakers would be placed so the woofers are 107 inches from the rear wall and 50 inches from the side walls. Your listening position should therefore be placed 107 inches from the wall behind you. At this point there should be a triangle with angles of 60 degrees at each corner.
These diagrams shows the Cardas ratios for speaker placement regardless of actual room measurements. These ratios are for placing speakers in a room which is longer than it is wide and using the long portion of the room for front to back placement. The ratios are different for using the longer walls as the rear and behind the listening position walls. For those who place their speakers along the longer walls in the room the ratios are reversed; the placement from the rear wall is 27.6% of the total distance from the rear wall and 44.7% of the distance from each of the respective side walls. Again, if your room is 20 X 15 feet and you place your speakers so the longer wall is the rear wall then you would place them so the distance from the rear wall would be 50 inches and 107 inches from each side wall. Your listening position would be placed so your ears are 55.2% of the distance from the wall behind you (100 inches) and centered between the speakers. That would mean 80 inches from the wall behind the speakers.The angles of the corners of the triangle from your listening position will be different than if you used the shorter wall as the rear wall of your listening environment. Note that your ears should be placed at the intersection of the lines from the rear corners to the speakers cones. This should be just about at 55.2% of the length from the wall behind you.
The difference in apparent measurements in the room diagrams is from the “Golden Triangle”, which calculates ratios for a perfect listening environment of 26 X 16 X 10 feet. In each line below the first number is the ratio in the golden triangle. The second number in each line is the number which we are concerned with here. It is the actual percentage of room length or width which dictates where speakers are placed. These are the numbers which I am using for actual measurements in this guide. Note that in these diagrams the actual listening position is never numerically noted so I have given them to you in the text of this guide.
Distance/Ratio
Distance Ratio Numerical Percentage
Speaker to side wall:
RW x .618 5 .276
Speaker to rear wall:
RW x 1 8 .447
Speaker to opposite wall:
RW x 1.618 13 .724
Speaker to speaker:
RW x 1 8 .447
For those unfortunate enough to have a square listening environment you can still use these ratios to your advantage. Your speakers should be placed so the woofers are 27.6% of the distance from the side walls and 44.7% of the distance from the rear wall. Your listening position will be centered at the intersection of the line from the rear corners bisecting the speakers.
3) The Allen Perkins method dictates 1)that the listening position will be near the wall behind you so that bass is accentuated while attempting to minimize sonic interference, 2) the listening position will be placed ¼ of the length of the room from the wall behind you and the speakers placed ¼ of the length from the rear wall and the side walls. It also dictates that minor speaker adjustments can be made along the length or width of the room to fine tune lower frequencies. To tune the mid-bass the speakers will be adjusted along the width of the room and for the lower bass the length of the room is the axis of adjustment. For the first method, the listening chair is placed near the wall behind it and the speakers are placed in a wide stance at approximately ½ of the distance from the rear wall and ¼ of the distance from each side wall. This gives a very wide soundstage after final adjustments have been made to speaker placement. The listening position not at a fixed ratio from the wall behind it but is placed a short distance away from the wall and it is recommended that some sort of sound absorbing material be placed behind the listening position. Generally speaking the listening position will be between 1 to 3 feet from the wall behind it. Make sure your system is wired in phase. This method is used when the rear wall is the longer of the walls in the listening room.
4) The second method dictates that the room be divided into sixteen equal sections with the length of each wall sectioned into quarters. This method is used when the side walls are the longer walls of the listening room.The listening position is ¼ of the length from the wall behind it. The speakers are placed ¼ of the length from the rear wall and ¼ of the width of the room from each of their respective walls.
5) This is what TNTTNT had to say about standing waves. There is also a graph to show the waves that are generated with a 40hz test signal.
40hz equates to a 14 foot distance between sound waves reflecting, which isn't far off my distance from wall to wall on listening axis. The other dimension is about 35 feet.
The way you get to 14 feet is simple. Sound travels at 1132 feet per second. It takes half the wave distance to generate the amplified node.
1132 feet divided by 40hz is 28 feet. Therefore the wavelength distance of a 40hz signal is 28 feet. We need only half this distance to generate a node, hence 14 feet. This matches the wall to wall measurement.
I bet you all the guys here have these nodes. Bigger rooms are better because you still get nodes, but they are lower and close to inaudible. Also the difference between the nodes generated (Several are not just at 40hz as in my example) get smaller, and the gives a flatter feel to the response.
I bought a sub and parametric equaliser to plump the the troughs in my graph, while cutting out 40hz before it gets to my sub amplifier.
I think this is why some speakers suit different room dimensions. A lot of speakers start fading in volume way before you get to 40hz. Perversely, this deficiency may be compensated by a 14 ft room.
>> The line should be flat (The yellow line). The huge peak in volume at 40hz and 150hz is due to the room rebounding sound waves and amplifying these frequencies. They are call room nodes and determined by the speaker placement and shape and size of room.
> >
> > For speaker placement you need to consider: -
> >
> > - choice of lisatening room for size - Larger is better for flatter response
> > - Shape - Cubic rooms where height, length and width are the same are an acoustic nightmare. Rectangular rooms are better
> > - Listening on the longest dimensions of the rectangular room.
> > - Speaker placement - placing speakers at on third of room points reduces room nodes
> > - Furniture and room fabrics/draping will affect sound waves rebounding and room nodes, so moving this can have an effect on sound
6) here are other considerations before you can get every bit of music out of your system for which it was designed. First, there is the matter of final adjustments. When initially placing your speakers you should place them so there is no toe-in. After you have made all your measurements then you need to adjust the forward/backward placement of either one of your speakers. It doesn't matter which speaker you choose, but you will be adjusting one or the other in small increments as small as 1cm at a time. You keep adjusting until the music is correctly centered to your ears. This is necessary due to the way we actually hear. It may sound counter-intuitive at first, but it really does work. This is the part that tends to take the longest for most people. It helps if you have someone who will move the speakers for you or who you know has very good hearing while you adjust the speakers yourself. After you have the music centered then you can toe-in. Generally speaking you want to toe-in so the speakers are pointed to a point roughly 6 inches to 1 foot behind your head. This will be the fine focusing of your speakers. You want to avoid having the sound centered too close to your head so the soundstage will not sound squashed or too wide so the soundstage sounds unnaturally wide and disjointed. One thing I have forgotten to mention is that your tweeters should be placed so they are on approximately the same height as your ears when you are sitting in your listening seat. This is due to the direct sound of the shorter wavelengths in contrast to the less easily detectable sound source of longer wavelengths. This will go a long way toward making the soundstage in your final adjustments sound as natural as possible.
7) Other considerations are room treatments, furniture placement and subwoofer placement. Room treatments and subwoofer placement are too broad for proper detail here . Furniture placement can play a big role in your listening enjoyment. It matters greatly what kind it is, what it's made of and where it is in the room. Large cushioned furniture can absorb a lot of sound and will tend to absorb the higher frequencies the most. The same goes for large rugs, especially those with that are thick and/or have substantial padding underneath. Large bookcases can scatter sound waves helping to diminish standing waves if they are open but if they are enclosed they can often be considered to be the same as walls. Sound will bounce off the hard enclosures instead of being dispersed by the numerous books and objects held within. It is often best if you have a minimum of furniture surrounding the area where you place your speakers due to sound wave dispersion and absorption. Not all of us have the luxury of having a dedicated stereo room. It is also good if you can have a minimum of different sized furniture placed haphazardly around the room. This can create a sonic nightmare that is difficult to rectify without removing the offending furniture. Due to the aesthetic preferences of lovers, spouses and whatnot that isn't always practicle. Suffice it to say that large enclosed furniture can essentially change the dimensions of the room by becoming de-facto walls themselves. Speaker placement should be adjusted accordingly if they are in that side of the listening room. By large I mean any piece of furniture that is taller than the speaker height when they are in their final position and which takes a lot of lateral space. For example, I have two stacked bookcases which stand 5 feet high and are 8 feet wide. These can be considered to shorten the width of the room by 15 inches on that side since any waves won't be bouncing off the wall behind them but off the bookcases themselves. Ideally it would be nice to have nothing in your listening room except your equipment and a place to sit, but this is unrealistic for most of us.
8) I hope this guide has been of help to you. I would like to thank again TNTTNT, Cardas Inc. and Allen Perkins for their valuable information. I cannot include near-field speaker placement since I have never used it and know nothing about it's actual application.
If there is anything that can be done to make this guide better don't hesitate to let me know. I am always willing to learn anything new which helps make the music better for all of us and am willing to pass on any good information.
