Special Treatment

Have you ever recorded and mixed a project in your studio only to find that what sounded great in your control room sounds completely different on other
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Have you ever recorded and mixed a project in your studio only to find that what sounded great in your control room sounds completely different on other systems in other places? This common scenario is the bane of personal-studio operators, and is often due to working in a room that has received no (or improper) acoustical treatment. Obtaining quality audio has as much to do with acoustics as it does with purchasing the right gear.

The trouble is that, as most personal-studio owners will attest, acoustical design and treatment can cost just as much, if not more, than good equipment. What's more, many personal studios are located in spaces that are less than ideal, such as old garages, converted bedrooms, basements, living rooms, dining rooms, and commercial offices. These rooms present personal-studio operators with a number of challenges that aren't an issue at multiroom commercial facilities, which typically have many more resources, both financially and in terms of space.

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FIG. 1: This graphic shows how sound reacts when it hits a wall made of sheetrock. Most is reflected back, but enough gets through to cause potential problems with neighbors and others on the outside. (Special thanks to Auralex Acoustics, Inc.)

Maximizing your studio's acoustics is not an insurmountable task and can be accomplished without breaking the bank. As with most endeavors, the trick is to do your homework, devise a realistic plan, and make the right decisions along the way.

Assessing Your Space

Unless you are in a remote location where there are no neighbors nearby, you must account for how the sound behaves within your studio (or within a particular room in your studio), and how much of it is escaping beyond the studio walls (see Fig. 1).

Russ Berger, president of the Russ Berger Design Group, an acoustical and audiovisual consulting firm based in Addison, Texas, explains that acoustical consultants analyze a number of different issues when making an initial assessment. “Sometimes there are problems in multiple areas: you may have poor energy in the room, and for some reason the low-frequency energy does not sound right.” In some cases, things sound entirely different when panned from left to right. “Perhaps we can fix that second problem,” he explains, “but we may have to knock out a wall and build it back differently.”

The problem might be as basic as silencing a noisy air-conditioning unit.

“Sound isolation is one of the first areas that might be addressed for acoustical performance,” says Richard Schrag, principal at Russ Berger Design Group. Noise and vibration control is an important aspect. “This generally has to do with the noise that comes into the room from air-conditioning systems, HVAC [heating , ventilation, and air conditioning] systems, or in building vibrations that would be induced into that room structure,” says Schrag. “The key is getting the room quiet so that you can capture a clean signal within the recording studio or, in the case of a monitoring environment, to be able to clearly hear what you have in terms of your program signal versus what you have in your room.”

Don't, however, confuse sound isolation with the acoustic treatments used within a room. “There are those who think that the materials that are placed on the walls or the ceiling to absorb the sound within the room will help to reduce the noise that leaks out to other spaces,” points out Schrag. “Those are separate issues, and what you do to control the sound from getting out or getting in does not help what is going on inside the room and vice versa.”

What methods are used to achieve sound isolation? “Stopping the sound with mass would be number one,” says Bob Hodas, engineer, acoustic expert, and consultant. Mass is particularly effective for stopping low frequencies. “Lead-impregnated vinyl, cement walls, sand-filled cement block, or a combination with air spaces in between, are all effective but expensive,” Hodas explains. He offers this suggestion for those on a relatively tight budget: “The most basic and cheapest method is a couple of layers of sheetrock that are applied with the seams offset so that you don't have any possible air leakage. Stagger the seams.”

Another relatively inexpensive approach is to cover any windows with a layer of thick Plexiglas. “That's a cheap method that buys you another layer,” says Hodas. “Windows are notoriously bad in inexpensive houses. So you could still get light, but have an extra airspace, with an extra windowpane for isolation. If you can't afford to buy triple-layer windows, go to the plastic store and buy some Plexiglas.”

The ideal approach is to “float the room.” Hodas explains: “The walls would be hung on resilient channel [a metal framing for hanging sheetrock in a way that adds to sound isolation] so that the inner structure would be completely isolated from the outer structure.” Unfortunately, this method is more likely to be practical and economically feasible in commercial or high-end project studios, rather than in typical personal setups.

Diffuse and Absorb

Once you've isolated your space as much as possible, the next step is to treat the inside acoustics. “Within the room, you need to have a monitoring environment or a recording environment where the room acoustics support that activity,” says Berger. For monitoring purposes, achieving clean imaging is the goal; for tracking, studio operators want a room that simply sounds good.”

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FIG. 2: This photo, from Studio Jory in Fairfax, California, shows a recording room with dual-purpose panels (from StudioPanel), hung from hooks. One side is a diffuser and the other an absorber, allowing for custom tailoring of the room acoustics for specific projects.

But what happens if your tracking room is the same space in which you monitor? There are answers, as long as you're willing to compromise a bit. “If you are recording yourself in there, you are on headphones anyway,” says Berger. But if other musicians are being recorded, a little bit of trial and error is required to achieve good sound. “If you have a drum kit sitting six feet away from you, obviously you can't turn your monitors on; you must monitor on headphones. But headphones do not behave the same way as monitor speakers.” The secret lies in clever microphone placement, and plenty of time for playback and adjustments.

Anthony Grimani, president of Performance Media Industries (www.pmiltd.com), an acoustical and audio-visual consulting company based in Fairfax, California, suggests that studio operators equip dual-purpose spaces with adjustable acoustics. “What you can do in a project studio,” he explains, “is to set up an acoustic-treatment scheme that you can move around. Instead of screwing and gluing treatment panels to the wall, you can have things that clip on to the wall that you can take off,” (see Fig. 2).

Those working in multipurpose spaces must accept that compromises need to be made. “It makes it even more challenging when you are trying to do both things out of the same room,” Berger says. “You must know what it is that you are trying to accomplish. What are you willing to live with? Every project is a compromise. There are always constraints — either with your building, your budget, the schedule, or your expectations.”

Acoustics First

Before going further, it's important to define the basic types of acoustic treatment. As its name implies, absorption utilizes absorptive materials to deaden or control specific frequency ranges. Diffusion takes a specific reflection and breaks it up in time or frequency. The sound waves are dispersed, and reflect off the diffuser at different angles. The net result is to alter the character of the original reflections by breaking them up into smaller, diffused sound-energy fields. That can make the room sound larger and give the sound a smoother, less fatiguing character. (Note: not all diffusers are the same. Some are broadband and some are narrowband.)

Although the term bass management is often used in reference to surround-sound systems, in the acoustical-treatment world, it refers to the extremely important task of controlling the bass frequencies. That is primarily achieved with bass traps, which are absorbers for specific low-frequency ranges.

Finally, room optimization refers to finding the optimal speaker/listener placement, and, if you're able to construct your space, the best dimensions for a given purpose.

Factoring It In

When designing a space for recording and monitoring, acousticians take several factors into account: the volume of the room, its shape, angles, and the finishes that are on the walls, ceiling, and doors. Acousticians try to ameliorate any problems with solid acoustic design.

A misconception is that you can compensate for bad acoustics with gear alone. “People think that they are going to be able to overcome acoustics with equipment, and you just can't,” says Berger. “By the time you get a foot or two away from the monitor, all of a sudden the room has a larger impact on what you are hearing than the speakers do because you are listening to the reverberant energy and decay.” To avoid problems, Berger advises studio owners to invest in acoustics first before making large equipment purchases. “That will probably save you the greatest amount of money in the long run,” he says.

It should be noted that equalization is an important aspect of tuning a room, but it must be done in conjunction with acoustical treatment to be effective.

As a general rule, square rooms tend to cause more acoustical problems such as standing wave resonances, which can cause peaks and dips in the frequency response and long bass-decay times. Rooms that have dimensions that are multiples of each other — for example, 8 × 16 feet — can also be problematic. Rectangular and irregularly shaped rooms are generally better.

Location Is Key

When treating a room's acoustics, figuring out the right acoustical materials to purchase is only half the battle: once you have them, you must determine where to put them.

“Dealing with acoustical problems has as much to do with where you put the materials as how much you use or what the materials are made of,” Schrag explains. “Do-it-yourselfers can sometimes get into trouble — they might have the proper materials, but they are putting them in places where they are not going to be effective.”

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Fig. 3: Sit at the monitor position and have someone move a mirror along the wall. Where you first see the face of the monitor is the first-reflection point. Repeat for other side, the back wall, and even the ceiling, if possible. (Special thanks to MSR, Inc.)

In general, the most important place to put acoustical treatments is at the first-reflection point (also known as first-order reflection), which is the point on the walls and the ceiling that directly reflects your monitors' sound back to your ears. Hodas describes the first-order reflections as “a reflection that's short enough that your brain can't separate it out from the direct sound of the speaker. Let's say a reflection that arrives no more than 18 to 20 ms after the direct sound. For frequencies above 400 Hz, it's like billiards — it's simple geometry.”

Grimani and Hodas recommend the same procedure for figuring out the first-reflection point. Sit in the mix position, and have somebody walk back and forth along the walls on your left and right while holding a large mirror flat against the wall. The points on each wall at which you see the speaker face in the mirror are the first-reflection points (see Fig. 3).

There isn't universal agreement as to what is the best way to treat a first-reflection point. “You're going to find some people who think you should diffuse first-order reflections,” says Hodas, “and then there are others who think you should absorb first-order reflections. That's just the way it is. People have different philosophical approaches. I like to absorb the front reflections and diffuse the rear reflections.”

“You want to make sure something's there, either an absorber or a diffuser,” says Grimani. “And you want to put the same thing on the back wall because the reflection off the back wall can be just as strong as the the one coming from the side wall. So you want to make sure there's something on the back wall. That's the wall that's behind the listener, not behind the speaker.” You can do the mirror trick to locate reflection points on the back wall and even the ceiling.

Taking Control

While most audio professionals recommend enlisting the services of a qualified acoustical consultant, reality dictates that that isn't financially feasible for many personal-studio owners. A less expensive solution is to use one of the increasing number of acoustical kits that are available on the market.

The Maryland-based acoustical-treatment manufacturer RPG Diffusor Systems, Inc., offers modular packages that start the customer off with a base configuration, allowing for expansion as budget allows. The company also sells software packages, such as Room Sizer and Room Optimizer (see Fig. 4) that enable studio operators to model their spaces before purchasing treatments.

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Fig. 4: RPG Diffusor's Room Optimizer software (Win) can calculate the optimal listener and speaker placement based on your room dimensions, speaker type, and other variables.

Developed by Performance Media Industries and distributed through Media Specialty Resources (MSR), Inc., StudioPanel is a kit system that was specifically designed with personal and project studios in mind. Customers enter their room information into a form on the MSR Web site to determine which configuration best suits their needs. A number of accessories are optional, including acoustical measuring devices and an audio CD featuring test tones.

At Indianapolis-based Auralex Acoustics, Inc., acoustical-treatment systems are designed to provide quality while remaining affordable. Through a form in its catalog, the company offers free room analysis: customers submit information such as budgetary constraints, measurements, layout, and the make and models of their loudspeaker systems (if available). Once the information is submitted, an Auralex acoustician will suggest a suitable product or kit.

Setting Your Budget

There are many opinions regarding how much money should be invested into properly treating a space. Schrag suggests that the dollar amount that is spent on acoustics and interior design should be equivalent to what is spent on the actual recording equipment.

Jeffrey S. Madison, director of the pro audio division of RPG Diffusor Systems, advises studio operators to apply “the weakest link” concept: “If you are saving money in one area — for example, in preamps or acoustics — to buy nicer microphones or monitors, you should reevaluate your budget and try to strengthen the chain at all the links,” he notes. “Otherwise, the system is compromised by that one link that got left behind.” A stronger overall chain will produce better results.

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Fig. 5: Best results are usually achieved with a mixture of treatments. This graphic shows a room with absorbers, diffusers, and bass traps. (Special thanks to MSR, Inc.)

Jeff Szymanski, chief acoustical engineer at Auralex, pegs the average investment at around $1,000. “Some people can get away with — or settle for — around $400 or $500 worth of treatment, and it's not perfect, but the room is much more usable,” he explains. “Then there are people on the other end of the scale that might be spending $1,500 to $2,000 to get a more complete package.”

At the same time, there is no hard-and-fast rule on how much acoustical treatments should cost. “People can spend $8,000 on their gear and still need $2,000 worth of treatment; other people can spend $50,000 on their gearand need only $1,000 worth of treatment,” Szymanski points out. “There are so many variables: the shape of the rooms, the surfaces, the speakers you are working with, your budget, and the placement of everything in the space.”

In many instances, the best solution combines bass traps, absorption, and diffusion in a coordinated acoustical strategy (see Fig. 5).

Low-Budget Solutions

Bearing in mind that every space and circumstance is different, several of the experts were asked to generalize what they would prioritize if the budget for acoustic treatment was limited to about $500.

“If you have only that much money to spend, you want to treat the first-order reflections, and you want to make sure that your speakers and your listening position are in the optimized position,” says Hodas. Proper positioning, he says, “can eliminate at least half the problems that everybody has. That's something that you could pay a professional to consult with you about. An acoustics professional could get you that information without breaking your budget. Hodas says that you can also use a program such as RPG's Room Optimizer to try to determine optimal speaker/listener positioning.

Grimani gives the following advice. “If you have limited funds, then it's really important to treat the room with either absorption or diffusion. You also want to get rid of slap echoes [sound reflecting back and forth between parallel walls]. You have to figure out what things are affecting the sound the most. First reflections are one, strong slap echoes are another. And the third thing is bass resonance, which is when you get this really loud, whompy bass. If you're mixing for what sounds right in your room, you might end up making it bass shy because you have a strong peak in the bass. What do you deal with first? That's kind of difficult. I think it all depends on what's the worst problem. If you need to get a good bass trap, you're pretty much going to spend your $500 right there.”

Szymanski concurs on treating the low frequencies first, especially if customers have structured their budgets to allow them to phase in acoustical treatments as finances allow. “Treating the low frequencies is probably the biggest challenge in any room, so where we tend to start people off, if they have [only] a few hundred dollars to spend, is with the low frequencies,” he says.

No-Budget Solutions

But what if you don't have extra money to spend on acoustic treatment? It then becomes necessary to rely on the materials you already have on hand, although improvements will be minimal compared to what you could get from dedicated acoustic treatments. Furniture; old, folded-up packing blankets; and careful placement of well-stocked bookshelves have all served those who needed to improve the acoustical behavior of their recording spaces for next to no money.

“A bookcase with books at all different depths placed behind you, or at the first reflection point off the left wall or the right, could be a diffuser,” says Grimani. “Not a great one, but better than the flat surface of the wall.”

Depending on what they're made of, drapes can be used as improvised absorbers. “Sometimes they don't absorb at all, so you have to be careful,” warns Grimani. According to Hodas, natural fabrics are superior. “The best materials to use are heavy wools or velvetlike theatrical curtains.” He warns that you don't want to use drapes with plastic backing or extremely tight weaves.

In some cases, it's advisable to weigh the cost savings involved in treating your space on your own versus the time it might save to hire a professional acoustician. “Very often, what you are trading off is the efficiency by which you can get the work done within the space — especially if you are talking about having the control room and the recording environment in the same space,” notes Schrag. “It requires a lot more back-and-forth, trial and error, and experimentation to achieve the end results that you are looking for.”

A Complete System

Berger emphasizes that acoustics should be regarded as a system like any other in the professional audio field. “[Studio operators] need to think about it as a system of materials and techniques, so that they can create an environment that works.”

One of the best ways to do that, according to Szymanski, is to treat everything as evenly as possible. “Don't over-absorb the highs or lows or anything in between — just get even, broad-based control,” he advises. “You want to make the sound even across the board so that what you are hearing from the speakers is what is coming from the speakers, and the room is not adding anything to that.” Unless, of course, you want your recordings to feature a bit of the room's ambience.

Ultimately, dealing with acoustics is something that personal and project studios cannot avoid — or solve by integrating different audio equipment into their setups. “One of the biggest mistakes I see people making is that they just ignore acoustics completely,” Szymanski observes. “They are constantly upgrading their gear and trying out new electronic solutions to something that is not an electronic problem.”

Carolyn Heinze (carolyn@carolynheinze.com) works from her office in Vancouver, British Columbia, Canada.

STUDIO ACOUSTICS DOS AND DON'TS

  • Don't confuse sound isolation (keeping out external sounds and keeping internal sounds from escaping) with acoustic treatment. They're separate issues that must be addressed as such.
  • Do find and treat the first-reflection points. Controlling first-order reflections is key to a better sounding room.
  • Do treat the low-frequency energy in your studio. Controlling bass is key to a room that will yield accurate mixes.
  • Don't devote your entire studio budget to gear. Save a sizeable portion for acoustical treatment.
  • Do find the optimal speaker and listener positions. You have several options, depending on budget: consult an acoustical expert, take advantage of the companies offering free room analysis, or consider a software solution such as RPG's Room Optimizer.
  • Don't expect guerilla treatments to be as effective as dedicated acoustical treatments. That said, items such as a full bookcase (diffuser) and drapes (absorber), when properly placed, can have some effect.

RECOMMENDED READING

Building a Recording Studio, by Jeff Cooper (Synergy Group, 1984)

Master Handbook of Acoustics, by F. Alton Everest (McGraw-Hill/TAB Electronics, 2000)

Project Studios: A More Professional Approach, by Philip Newell (Focal Press, 1999)

Sound Studio Construction on a Budget, by F. Alton Everest (McGraw-Hill/TAB Electronics, 1996)

MANUFACTURER AND CONSULTANT CONTACTS

Auralex Acoustics, Inc.
www.auralex.com
www.acoustics101.com

Bob Hodas-Acoustic Analysis
www.bobhodas.com

Media Specialty Resources (MSR), Inc.
www.msr-inc.com

Performance Media Industries
www.pmiltd.com

RPG Diffusor Systems, Inc.
www.rpginc/proaudio

Listen at: www.rpginc.com/listen/index.htm

Russ Berger Design Group
www.rbdg.com