Home Studio Acoustics: Speaker Placement

by Pablo Bellinghausen

Producing music of any kind relies on accurate monitoring, and professional studios spend a lot of money not only on the speakers, but in acoustically-treated, purpose-built rooms of just the right size and shape for optimal sound. In most project studios – even those with high-quality gear – one of the biggest challenges is setting up a space that will allow for the speakers to reproduce the sound as it is in the recording.

Mixing in a poorly set-up room with bad acoustics is like painting in a room lit by a dim, colour-tinted light bulb; you will have real trouble seeing what you are doing, you will struggle to discern details, and it will be extremely hard to differentiate colours; no matter how talented the painter, the final work will look strange and “off” in any other room.

Lotte-Both-LightsBad monitoring: like painting under poor lighting

Mixing in a well-designed, well-treated environment removes most of the guesswork from the process, making it more efficient, more pleasant, and less frustrating. Details are clear, instrument tonality can be trusted, and any problems become more obvious, and therefore easier to fix, ending in a far better result, which will translate into other playback systems. Unfortunately, most project studios in residential areas are in spare bedrooms, which are often small, have low ceilings, and have unhelpful proportions. Getting good results in that kind of space comes down to the following things, in no particular order:

• Speaker quality
• Room shape
• Speaker position in the room
• Acoustic treatment

All of these are critical and should not be neglected. Of course, speaker quality will depend on budget, and there is little one can do about the shape of a room, but assuming those are a given we can take a look at the other two. We will leave acoustic treatment for our next instalment and focus on speaker positioning this time around.
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The Reflection-Free Zone design

Although there are other designs out there which work better in large rooms, smaller professional control rooms nowadays will most often use what is called the ‘Reflection-Free Zone’ (RFZ) technique: RFZ-Control-Room-Large This design, in which the front walls are absorbent and angled a certain way, steers most “early reflections” away from the listening position and damps them as much as possible. Early reflections can enhance certain sounds at the recording stage, but in a monitoring environment they smear details, confuse the stereo image, and obscure the original sense of space in a recording, so getting rid of them is usually a priority. Early-Reflections On the other hand, the back wall is usually kitted with diffusers, which are reflective shapes mathematically designed to scatter the sound as much as possible.

UA Mercury DiffuserDiffusers like the Universal Acoustics Mercury scatter frequencies evenly in all directions

This configuration minimises early reflections, while at the same time leaving in some diffuse reverberation that adds liveliness to the sound in a way that doesn’t detract from the sound quality, yet eliminates the unnatural and oppressive sensation very dead-sounding rooms can give. To do this well is expensive, but knowing this technique will inform the positioning choices and the acoustic treatment that need to be applied in a control room, even on a budget.
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Speaker positioning in small rooms

In the real world, monitoring is an art of compromises, and monitoring accuracy is a goal that one can reach progressively with more and better treatment. However, an important first step is to choose the best speaker position. Here is what you need to take into account:
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Room symmetry and orientation

In many ways the most important thing when considering the placement of speakers is finding a symmetrical arrangement. This is because room reflections create wildly different frequency responses depending on the position, and if the left and right speakers don’t have the same reverberation pattern, they will sound completely different no matter what you do. It is like using one model of headphone for one ear and a completely different one for the other, even worse if anything!

The best orientation in most rectangular rooms is usually having the speakers on the narrower side, so that the reflections from the back wall (which will be loud and bright, since the speakers are basically pointing towards it) have to travel a longer distance, making them quieter and delaying them more. This is at the expense of louder side reflections, which will have to be dealt with through acoustic absorbers. However, if the only way to keep the speakers centered in the room is to use the longer side, then that’s a next-best scenario. In that case, the back wall will have to be deadened far more – we’ll go into more detail on acoustic treatment next time. Small square rooms are an acoustic nightmare, but they do allow a diagonal position which works acceptably well.Room-Orientation-Newest

Distance from the wall

In a small room, after having considered all the above details, the distance from the speakers to the back wall will most often be quite small, and some people can find that concerning; after all, the wall will indeed create cancellations and dips in the frequency response. However, the closer the speakers are to the back wall, the higher the frequency of the cancellations, and the easier it is to treat it with acoustic absorbers. Many manufacturers recommend placing the speakers as close to the wall as possible (whilst allowing a few centimetres for the bass port) and then adding strong acoustic treatment to dampen the back wall reflections.

Speaker-Distance

Genelec recommends the above for wall–speaker distance 

Due to phase reinforcement, close-to-wall placement progressively boosts bass frequencies, which is often not a bad thing with smaller speakers; however, if the boost is too strong (particularly with rear-ported models), most monitor speakers provide a bass EQ to straighten the frequency response, which works really well in most scenarios.
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Listening distance to the walls

It’s a good idea to avoid the middle of the room as a listening position, since is where the frequency response is the most uneven (you should also avoid the 1/4 and 1/6 ratios, for that matter). This is due to room resonances (called room modes, or standing waves), which cause not only huge bumps and dips in the frequency response of the listening position, but also causes sounds at those frequencies to “linger” for longer than the rest of the sounds, creating boomy bass, strange and indistinct midrange, and even certain notes to either “jump out” or almost disappear!

Standing-Waves

There are “room calculators” which involve quite a bit of maths in order to find the best listening position, but these only apply to a completely empty, untreated room in which all walls, ceiling and floor are made of the same material; as soon as one starts looking at real spaces, with different materials, equipment, shelves, and even beds, one ends up with completely different reflection patterns, which translate to different “best” positions. With the correct treatment, one should be able to overcome many of the major problems, but as a good starting point, it’s best to find a position that avoids the worst standing waves:

Best-Distance-from-Room

The Golden Ratio in Speaker Placement

There are many misconceptions about speaker placement, many in audiophile circles, and they stem from a misunderstanding of how sound waves behave in a small room. There is a school of thought that uses the golden ratio (1.618, which translates to percentages of 38% and 62%) on the speakers, in order to avoid standing waves.

The problem with this theory is not only that said ratio is very close to the 4th room node, but that the standing waves are a far bigger problem in the position of the listener than that of the speakers; the speaker’s sound will of course change depending on their position, but nothing special happens at that ratio; it’s the absolute distance from walls that makes a difference, no matter the ratio. Many of those calculators tend to put the listener uncomfortably close to the middle of the room, where the standing waves are strongest, and therefore into the worst-sounding place.

In most real-world home studios, the listening position will usually be a compromise, and following the above graph will let you avoid the main room modes, but it’s important to stress the fact that this is assuming bare walls and no acoustic treatment, so it is little more than a good starting point. Just remember, getting a bit closer to the speaker wall and further away from the centre of the room is usually better.
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Getting the angles right

The best angle for the speakers is 60 degrees, is so that the head and the speakers form an equilateral triangle. A wider angle will make you lose the ability to judge the correct level of instruments placed in the centre compared to those from the sides, making you bury the bass and vocals. Too narrow an angle, and you will lose the ability to pan instruments accurately.

The ideal distance from nearfield monitor speakers should be between 2 and 5 feet from your head (and using that same distance between the speakers to keep the correct angle), although in smaller rooms you wouldn’t want to get further than 4 feet. To a degree, the closer the speakers are, the drier (and therefore the more accurate) the sound will be, but any closer than 2 feet and the sound will not be represented properly, since nearfield speakers are designed to be heard at a certain distance. Speaker-Angle Some people prefer to angle the speakers slightly away from the head to aim somewhere slightly behind the head, to soften the tweeter’s top end a bit; this is mostly a matter of taste, although more than a few degrees will skew the frequency response of the speakers too much. Speakers are measured to have the desired frequency from the front, so that should ideally be the angle at which they should be listened.
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Stands or desk?

In a room without any furniture, the best sound comes from putting the speakers on professional stands, but who has ever seen a studio without a desk? The problem is that desks, mixing consoles and computer screens are large, reflective surfaces, and the sound will bounce on them and affect what you hear. Cheaper desks are also light and a bit wobbly; they will in that case resonate with speakers if they’re are placed on top of them, which will cause rattling and further sound degradation.

Monitor and DeskDesk reflections can be one of the biggest problems in a studio

To a large degree, the position of the speakers will depend on the size of the desk you already have, and the amount and size of the gear that needs to be on it; a desk large enough to support an 88-key controller keyboard will likely be too big to have speaker stands at either side, but for smaller project studios that work mostly “in the box”, it’s easy to get very small desks just for the computer and peripherals and keep the rest of the gear elsewhere in the room. If you are putting speakers on your desk however, foam isolators are a great idea, since they decouple the speakers and stop resonation. In most desks, the best position will be in front of the computer screen in order to avoid the reflections from it.

Recoil StabiliserThe Primacoustic Recoil Stabilizer can help decouple the speaker from the desk

How far from the ground the monitors will be is usually determined by the stands or the desk, although if at all possible it’s best to avoid them being in the middle of the room in terms of height (the above ratios work on vertical room modes as well). Speakers can also be slightly angled vertically as long as the sound is being directed the right way.

The optimal angle will depend on the design of the speaker, but it is good practice to keep the height of the ear between the tweeter and woofer height, whilst remaining slightly closer to the tweeter. This ensures that the phase relationship between the tweeter and the woofer doesn’t create cancellations around the crossover frequency. Vertical-Position

 

In our next instalment, we’ll see how to acoustically your home studio room to ensure the best sound from the position we’ve chosen. Until then, happy recording!