Monitors and Studio Acoustics
If you want to make the best-sounding tracks, a good monitoring environment is crucial. Huw Price recommends a holistic approach to monitor selection and room treatment.
We’ve run features on monitors, monitor setup and acoustic treatment before, but they’re so closely related that they really shouldn’t be treated as separate subjects. As usual, a balanced approach is needed to get the best results and value for money – and you need to think holistically.
If your room doesn’t have any form of acoustic treatment, you really should address this issue before spending anything on monitor upgrades. Otherwise, a pair of expensive monitors that are louder and have a wider frequency response might end up sounding worse than the cheap ones they replaced! Splashing out on ever-more expensive speakers in an attempt to solve your monitoring problems without addressing room acoustics is just throwing good money after bad. A moderate amount of acoustic treatment can dramatically improve the results you can achieve, even with modest monitor speakers, and treating your room can often be far more cost-effective than upgrading your monitor speakers.
Typical acoustic issues always include some combination of the following: comb filtering, standing waves, boomy bass and flutter echoes. Each of these is discussed in a separate boxout (see ‘Typical acoustic issues’, p26) so without further ado, let’s dive straight into the three main acoustic treatment methods.
Absorption
You can use equalisation controls on active monitors or a multi-band graphic equaliser on passive monitors to fine-tune minor frequency problems, but only after you have made some attempt to address acoustic issues. You can’t use EQ to cure flutter echoes, comb filtering or standing waves.
Acoustic foam has an open surface that allows soundwaves to enter and is full of air bubbles. When soundwaves enter the foam, friction occurs between the fibres, dissipating sound by converting it into heat. Fibreglass absorption products work the same. These products are cost-effective and give quick results. Check out Ghost Acoustics, Auralex, Primacoustic, Studiospares, Universal Acoustics and Real Traps for individual products and pre-assembled kits.
Bass traps
Although foam absorbers can be used to control bass, they have to be very deep to be effective at the lowest frequencies, and this is often impractical in small rooms. Many of the foam products are designed to fit into corners, where bass frequencies typically build up, which is an effective use of otherwise dead space.
Helmholz Resonators are among the best bass traps. They can be tuned to absorb the specific frequency that is causing problems in a room or they can be modified to widen their effective frequency range. Real Traps makes some well-regarded bass traps and MSR Acoustics has sophisticated spring traps that target the 30–100Hz range.
Diffusion
Unfortunately, overly absorbent rooms with little or no reflected sound are lifeless and unmusical listening environments that bear little relation to the real world. Monitoring systems will also have to be driven much harder to fill dead rooms with sound, so more amplifier power is required, which invariably involves more heat, distortion and listener fatigue.
It’s for this reason that most studio designers consider some degree of reverberation in control rooms preferable – but how can you have reflective surfaces without standing waves and flutter echoes too? The solution is to use diffusers.
Diffusers scatter soundwaves around a room in all directions, regardless of frequency. This differs from absorption and trapping because it is the only method that doesn’t involve the transformation of energy. Diffusion panels are particularly effective in home studio environments where small room sizes restrict the amount of space available for traps and absorption panels. According to acoustician Anthony Grimani of acoustic treatment product manufacturer MSR Acoustics, diffusers also improve the efficiency of absorbers, so you will need fewer absorption panels and less wall space will be used up. Diffusers will reduce standing waves and flutter echoes and there are various products on the market. Primacoustic produces the Razorblade and the Polyfuser, which is a combination diffuser and low-frequency bass trap that can effectively absorb low frequencies down to 45Hz. RPG sells a highly specialised MDF diffuser called the Diffractal and RPG’s Abffusor also performs absorption and diffusion duties. Auralex also produces a large range of diffusers, so it’s fair to say there are plenty of options out there.
Monitor setup
Once you’ve made some attempt to address the acoustic issues of your workroom, it’s worth learning some ground rules about how monitors should be set up in a studio environment. In a conventional stereo monitoring situation, both speakers must be positioned at the same height and the tweeters should be the same height as your ears when you are in your usual working position.
This explains why, in many pro studios, you will see monitors placed on their sides, usually on a shelf that’s integral to the mixing desk. Since the shelf is a fixed height, placing the speakers sideways is often the only way to align the tweeters with your ears. However, most speakers are designed to work upright and they generally sound better that way because there’s less interference from soundwaves reflecting off the surface of the mixing desk.
These days, few project studios will have mixing desks with meter bridges, so it’s worth considering how to arrange your monitors. You should always avoid putting speakers directly on resonant surfaces like shelves, desks or hollow boxes, because these will affect the sound of a speaker. An otherwise tight and well-controlled bass response can in such a situation quickly become boomy and flabby.
Hi-fi enthusiasts have been into speaker stands for years and they often pay more for their stands than for the speakers themselves. Fortunately, cheaper and more practical speaker stands are available for studio owners. Studiospares’ own brand stand (£16.80) is sturdily made with a weighty triangular base, a height-adjustable shaft and detachable carpet spikes. You can also get shorter speaker stands such as the K&M 26790 for shelf and desktop use.
Speaker isolation
Isolating the speaker from any resonant surface can further tighten up bass response and there are two principal methods of doing this. Firstly, you can reduce vibration transfer by minimising the area of physical contact between the speaker cabinet and the surface it’s resting on. Speaker spikes are ideal, especially on the bottom of speaker stands where there’s carpet involved. Unfortunately, spikes have a tendency to scratch wood or wood-effect surfaces, such as those you’ll see on many studio floors, so ceramic cone isolators are a preferable option in such a setting.
The second isolation method involves placing layers of acoustic foam between the cabinet and the mounting surface. Acoustic foam doesn’t transmit vibration, so this helps to provide some isolation. Auralex offers some very cost-effective solutions. More sophisticated products augment the foam with added mass from heavy metal plates and dense rubber and the Silentpeaks SPK Isolator and Primacoustic RX9 are among the best products of this type.
Positioning your monitors
Just about every high-quality speaker will supposedly have a flat frequency response right across its frequency range. However, the way a speaker performs in free space in an anechoic chamber and the way it sounds in the real world are inevitably different.
If you put a speaker up against a wall, the bass end will rise dramatically. This effect will be even more pronounced if you put speakers in corners. Sometimes active speakers are equipped with equalisation switches that can compensate if space restrictions force you to compromise your speaker placement, but as a rule you should keep them away from corners and walls. This is something that you’ll need to bear in mind when you’re considering your studio layout.
On the toe
Your working position should be exactly in the centre of the speakers and you will need to listen carefully to determine the correct amount of toe-in. If you don’t get this bit right, any panning decisions you make when you’re mixing will be sheer guesswork because your speakers won’t be imaging properly.
If you listen carefully to a well-mixed track, the lead vocal should sit squarely in the centre of the mix. The same goes for kick and snare drums. If any of these elements sound spread out or vague, turn each speaker towards the centre by a couple of centimetres until the audio image becomes solid and clearly located in the centre of the mix. Continue making small adjustments until you achieve solid centre images with the widest possible stereo image.
The amount of toe-in will vary depending on your listening distance and the distance between the speakers themselves. Also, some people prefer centre images to appear in front of their heads while others prefer them to appear between their ears, as if listening on headphones. You’ll soon discover what works best for you. If every element in the mix seems to bunch up in the centre and the stereo image seems too narrow, it means the speakers are too close together and/or there’s too much toe-in.
Choosing monitors
We’ve established that it’s important to know how to position and align speakers if you want to make meaningful evaluations, so let’s examine the various types of cabinet and drive units that are available. Active monitors have individual amplifiers built-in to the speaker cabinet to power the drivers. As well as making it easier for designers to control low-frequency damping and distortion, active designs eliminate the need for speaker cables and can save space. The crossover can operate at line level using smaller, less expensive components, and since each driver has its own amplifier, matching drive units with similar sensitivity becomes less crucial. Manufacturers can also install corrective equalisation controls to help the user overcome some issues in the acoustic environment. Some even come with measurement microphones and calibration software – see the frequency and phase alignment box.
Passive monitors require external power amps plus speaker cable to connect everything together. Throughout the 80s and 90s, most sound engineers relied on medium-size hi-fi speakers and many still prefer them. Lots of hi-fi speakers are easily good enough to use for critical listening and they’re more representative of the type of speakers that punters will be using when they’re listening to your mixes. So the argument is that if you can get a great result on your hi-fi-style speakers, your mixes stand a better chance of translating well to other domestic sound systems. The downside is that quality hi-fi speakers are often more expensive than active monitors these days and they’re rarely designed for prolonged high-volume use. Also, they’re usually engineered to make all music sound ‘nice’, so they’re more about entertainment than honesty. Buyer beware…
Evaluating speakers
Assessing unfamiliar monitoring systems with familiar material is always advisable. Most pro engineers carry around a selection of CDs that can help them understand how the speakers and room are behaving acoustically. A sparse track that has a very deep (preferably electronic) bass line with few overtones will tell you a lot about the bottom end. Don’t just listen for the amount of bass – you need to be able to distinguish the individual notes. Over some speakers the lowest notes degenerate into a messy boom – these are the speakers to avoid.
A properly mastered CD can also help you to assess the high-frequency balance and the amount of colouration in the midrange. If you are working in various studios or you are trying out monitors in shops with a view to buying, make yourself a compilation CD with mixes that you trust and take it around with you. Pretty soon you’ll be assessing speakers confidently and quickly. However, you can’t rely on CD listening tests alone. There are plenty of speakers that are fabulous to listen to but hard work when it comes to achieving a balanced mix. What’s more, the speakers might perform very differently in your studio from in the shop, so always take up any offer of a trial period. Obviously, this caveat becomes all the more important the more money you’re spending!
If you can’t bring the monitors home, take a laptop to the shop with a simple pre-recorded backing track and try balancing up a few mixes on various speakers. Keep things quick and simple by using the stereo outs from your computer or soundcard. Record each mix as an internal bounce and label them with the name of the monitors they were mixed on. At home you can compile a CD with all the mixes and play them on as many systems as possible. You’re checking how well they translate – the winner will be the mix that sounds the best on the widest variety of monitoring systems. The speakers that eventually win out might not be the ones you liked best in the shop – and once you get them home, remember also that even the finest speakers require a learning period whereby you can get used to their foibles, subtleties and peculiarities.
Making choices
We’d love to be able to say that spending ‘X’ amount of money will solve all your problems, but monitoring always involves compromises. Obviously everyone will have budget constraints, but as an overarching rule, when you’re putting a studio together – or updating/upgrading an existing one – at least some of the money should go towards acoustic treatment and proper speaker stands or isolation mounts. Then you’ll need to account for the size of your room and the type of speakers that will realistically fit in there.
Also carefully consider the type of music you’re interested in. If you’re primarily recording and producing classical music, for example, then ultra-low bass performance won’t be your main concern. However, if you’re into electronic music, dance or reggae, the bottom end will be crucial and you’ll need bigger cabinets or a separate subwoofer. Above all, our biggest piece of advice would be one that applies to all forms of technology, all the time: whenever possible, try before you buy… We’ve run features on monitors, monitor setup and acoustic treatment before, but they’re so closely related that they really shouldn’t be treated as separate subjects. As usual, a balanced approach is needed to get the best results and value for money – and you need to think holistically.
SEE ALSO
Choosing & Using Monitors (Feature)
Monitor Design (10MM)
This feature first appeared in Music Tech Magazine issue 90
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