How to improve your living room acoustics
2/2/2024
Translation: Eva Francis
If you want your speakers to sound good, the room acoustics have to be right. However, bass frequencies aren’t easy to control. Read on to find out whether your room is worth optimising.
This happened some years ago, but I still remember it as if it was yesterday. I was standing in the showroom of Swiss loudspeaker manufacturer Piega in Horgen. We were listening to music from high-end speakers bigger than a heavyweight boxer. Thick cables led to tube amplifiers – every speaker had its own separate amplifier. The entire setup was worth a six-figure sum. The sound? Outstanding. «What’s the most important thing if you want great sound?» someone asked a Piega employee, who answered, «the room.»
Piega doesn’t produce room acoustics products. With this in mind, I’d have expected their staff to downplay the importance of the room and emphasise the importance of the speakers. However, that would have been pointless, as we tested the cheapest Piega speakers shortly after and they sounded excellent, too. How come? Well, the showroom was acoustically optimised.
How good speakers sound depends heavily on room acoustics. If you’re unhappy with the sound of your system and are considering upgrading, you might actually be unhappy with the sound of your room. If this is the case, there’s no point in spending money on better speakers. Instead, you should understand the acoustics in your living room.
Trapped sound
A portable Bluetooth speaker sounds different – mostly better – outdoors than indoors. How come? Well, in a room, the sound is reflected by the walls, ceiling and floor. This creates plenty of unwanted effects.
First of all, you don’t need the reverberation of a room because it’s already part of the recording when you play canned music. Additional reverberation of the room impairs the sound precision. In other words, you’ll be less able to hear where the individual instruments are located in the stereo image.
In the case of live music with acoustic instruments, the sound source has no reverberation. It’s only created in the room. But even in this case, not every reverberation is wanted. In concert halls, a lot of work is put into getting the resonance just right. One of many factors is the reverberation time. Ideally, it’s around two seconds for medium frequencies, and slightly less for operettas so voals sounds clearer. In the Berlin State Opera, the ceiling was raised by five metres to increase the reverberation time from 1.1 to 1.6 seconds. This took seven years of building work. On top of that, 26,000 individual parts made of phosphate ceramics were produced to improve acoustics.
Reducing reverberation
Reverberation is particularly noticeable in an empty room, for example when you snap your fingers. As soon as you fill the room with a sofa, carpet, bookshelf and other things, there’s a lot less reverberation. So how do you reduce reverberation in a room? Furnish it. Using carpets and other sound-absorbing elements is particularly recommended in modern buildings that often feature tiled floors and other hard surfaces.
However, this doesn’t reduce all reverberations equally, as high frequencies are absorbed much more than low frequencies. The thicker a sound-absorbing element is, the lower frequencies it can absorb. Carpets and curtains only absorb high frequencies. To tame bass frequencies, absorbers need to be at least twenty centimetres thick – like a thick cushion, for instance. In other words, a fluffy carpet won’t do the job for low frequencies.
In a room’s that’s only furnished with thin sound-absorbing elements, the sound may appear muffled.
Well then, why not compensate for that with the equaliser? After all, who doesn’t love a lot of bass!? That’s a bad idea. But why?
Room modes – the problem with bass frequencies
Correcting the treble with an equaliser may work to some degree, but correcting bass won’t. Bass tones reflecting off walls, ceilings and floors don’t just lead to more bass. Instead, the bass is distributed unevenly throughout the room. As a result, you hear certain frequencies too loudly, others too quietly. In addition, you hear the same frequency louder or quieter as you walk around the room. How come? The answer’s room modes.
Room modes occur when the length of a sound wave corresponds to the length of a room. The length of a sound wave depends on its frequency. The lower a sound, the longer the wave. Certain frequencies are exactly as long as the room; or exactly half or a third as long.
If one of these sound waves is reflected by the wall, it looks exactly the same or mirrored on the way back as it did on the way there. As a result, the amplitude deflections are always in the same place in the room and the wave stands still instead of travelling like a regular sound wave. Of course, the «standing wave» isn’t actually stationary, but its shape always looks the same in the room when it’s travelling.
And you can hear that. These amplitude deflections add up – or they cancel each other out if they’re inverse. As a result, the sound wave is very loud in certain places and barely audible in others.
Source: wikimedia.org/Jkrieger
It gets really bad when a standing wave develops its pressure maximum exactly at the reflecting wall. If this happens, it’s thrown back with maximum force. At the opposite wall, the wave is at its maximum again and reflects strongly again. As a result, these frequencies diminish much more slowly than others.
This problem doesn’t only occur between the front and back walls of the room, but with the side walls, ceiling and floor, too. Bass frequencies spread out spherically in all directions. Therefore, the typical cuboid shape of an ordinary room isn’t suitable for good acoustics. Rooms with sloping ceilings and irregular floor plans are better, but they’re also less predictable.
The ratio of length, width and height of a room also plays a role. Several room modes overlap in a room with a square floor plan. This reinforces the impression of irregular bass distribution. Rooms that are exactly twice as long as they’re wide are also unsuitable. Rooms with an irregular aspect ratio, on the other hand, don’t have fewer modes, but they’re distributed more harmoniously.
Detecting room modes
Before you can take corrective measures, you need to identify the room modes in your room.
The problematic frequencies can be calculated by dividing the speed of sound (344 m/s) by twice the length of the room. In a four-metre-long room, that’s 43 Hz. Multiples of this, i.e. 86, 129 and 172 Hz, are also problematic.
The same applies to the room modes of the side walls and those between the ceiling and floor. In addition, there are room modes that go around the corner and have less of an effect.
Fortunately, you don’t have to calculate all this yourself. Enter the length, width and height of your room and the online tool amroc does the maths for you. The tool shows you the frequencies as well as a 3D view of where the room modes are.
Source: David Lee
Keep in mind these calculations may differ from reality, as the room furniture – a large mirror cabinet, for instance – also absorbs or reflects sound. I can’t use the tool to calculate my living room, as it has a complicated floor plan with 120-degree angles, and one of the walls is broken up by a wide entrance.
In this case, nothing beats listening tests. Connect a sound generator with a freely selectable frequency to your sound system. I use the free app Sonic on iOS, but any app will do.
The calculations of the online tool serve as a guide as to where you need to listen with which frequencies. Since I can’t use the tool for my room, I need to invest more time in experimenting. But I know, for example, that my room has a problem at 97 Hz. If I sit directly in front of the speakers, I can hardly hear this frequency. If I sit at the wall or window, however, it blows me away.
Source: David Lee
The bass is usually loudest at the walls, especially in the corners of the room where two room modes overlap.
What to do against room modes – avoid or absorb them
You can’t change the geometry of a room or the frequencies of a song. So what can you do about room modes?
You can’t get rid of them entirely – and you don’t need to. Even a fully optimised music studio has room modes. However, they’re mitigated by using thick absorbers. And in a studio, a listening position with no room modes is chosen.
Reducing room modes is more difficult in a living room than in a studio. For one, you can’t sit anywhere in the room to listen to music. In my home, for example, there’s only one place for the sofa and only one for the speakers – and they’re not ideal for each other.
Source: David Lee
In other words, I can’t listen to good quality music on the sofa without making the living room look unappealing and impractical. The solution is to place an easily movable armchair straight in front of the speakers.
What about absorbers? An absorber is most effective in the corner of a room. On top of this, it needs to be thick and reach up to the ceiling. In theory, you could buy a foam rubber mattress at a DIY store, roll it up and place it in the corner of your room. But who wants to live in a home with foam mattresses in the corners? After all, you’ll need more than one of them. Of course, you could buy bass traps that are designed for that exact purpose. They look nicer, but they’re expensive and quite large, too.
The Hofa Basstrap V2, for instance, currently costs 185 francs or 199 euros at Thomann. You’ll need at least two of them per corner of the room. Four or six would be even better for the very low frequencies.
Source: hofa-akustik.de
A top tip that doesn’t cost a thing? Don’t place the speakers directly against the wall, but move them away at least 20 centimetres. This reduces bass reflections by taking away some of the energy of the low sound waves before they reach the wall.
The same applies to the subwoofer. Don’t place it directly against the wall and never put it in the corner. Right in the middle between two walls isn’t great either. In a 5.1 system, placing it in the middle between the centre speaker and the left or right front speaker is usually recommended.
Make sure the distance from the wall isn’t exactly a third of the distance between the speaker and the listening position or the frequency will be cancelled out by the rear wall reflection. If a frequency is cancelled out, it’s almost inaudible. It’s a similar phenomenon to room modes, but with only one wall.
Because of this frequency cancellation, manufacturer QSC, for example, recommends placing the subwoofer close to the wall after all. This ensures that the problematic frequency is above the frequency range of the subwoofer. In my opinion, however, it’s better to solve the problem by adjusting your listening distance, if possible. In any case, it’s worth experimenting with the position of the subwoofer. Place it on a mobile base until you’ve found the sweet spot.
Not every room can be optimised
If you’ve read this far, you’ll know there are limits to room optimisation – especially if a living room is already furnished. If this is the case, there are too many things to look out for. The sofa needs to be in a nice place, you can’t put anything in front of the window, the cables shouldn’t be visible, the sockets need to be in the right place and so on. Changing things around might improve acoustics, but would destroy the comfort of your living room.
I know there’s no good solution for my current living room. And that’s a helpful insight, too, as I’m not tempted to spend thousands of francs or euros on speakers only to be disappointed by the result.
Does it mean I can’t enjoy great acoustics? Not at all.
Safe option: headphones
I like using headphones. Not only when I’m out and about, but also at home. One of the reasons why I like headphones is because they solve all my room acoustics problems. If I ever do invest a lot of money in audio equipment, I’ll probably get new headphones rather than speakers.
If you like this idea, you need to know that music from headphones doesn’t sound the same as music from speakers. With speakers, each ear hears roughly the same amount of both channels, at least in the optimum listening position. But there’s a slight time lag. With headphones, however, both channels reach the ear at the same time. However, left and right are largely separated – a bit less with open-back headphones than with closed-back headphones, though.
Some headphone amplifiers have a crossfeed function to simulate the acoustics of stereo speakers. This function artificially creates overlapping channels and time lags. I tried it with the headphone amplifier ADI-2 DAC from RME Audio, but the effect didn’t knock my socks off. It didn’t sound like listening to music playing from speakers. Having said that, I almost always like the headphone sound without crossfeed function, so that doesn’t bother me.
Unsafe option: short listening distance
I’m the proud owner of a cheap Bluetooth speaker, the JBL Flip Essential. The other day, I was listening to music in bed with the speaker placed right on top of my chest, almost at my neck. To my surprise, it sounded really good.
That made me think of trying out table speakers. At a listening distance of about 60 centimetres, room acoustics should only play a minor role, right? Well, at least that’s my hope, as my table isn’t placed well acoustically.
If this simple trick eliminated any room acoustics problems, these very strange-looking neckband speakers would suddenly make sense.
Conclusion: know what you’re getting yourself into
Room acoustics isn’t a simple matter. On the one hand, it’s important to know about it. After all, if you’re unhappy with the sound in your living room, there’s no point in buying better speakers without examining the acoustics.
On the other hand, not every living room can be optimised with reasonable effort and a satisfactory result. Room geometry, the arrangement of windows and furniture and other factors determine some of the acoustic properties. Effective bass absorbers are thick and not pretty.
So your first step has to be finding out whether it’s worth optimising your room at all. If it’s not, think about alternatives. These range from high-quality headphones or a separate music room to finding a new home.
And even if you decide to try room optimisation, know it’s a never-ending story. The choice and positioning of absorbers alone is a science in itself. Audio forums are full of people who can’t stop optimising – and often make the situation worse. In any case, keep the 80-20 rule in mind or you’ll end up with a new, unwanted hobby.
The simplest and most effective way to improve acoustics is by experimenting with the position of the speakers and the listening position. Identify the room modes and you’re halfway there.
Header image: Flickr/Jan Hammershaug
David Lee
Senior Editor
David.Lee@digitecgalaxus.chMy interest in IT and writing landed me in tech journalism early on (2000). I want to know how we can use technology without being used. Outside of the office, I’m a keen musician who makes up for lacking talent with excessive enthusiasm.
