Shootout at EQ Corral

Armchair theories abound. Fact-based (partially) notions on how a studio should be treated to create the most accurate sonic response are legion. But you know, it’s one thing when you’re talking about a ground-up build-out of a space purposely designed or remodeled as a recording studio or control room, where you have
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Armchair theories abound. Fact-based (partially) notions on how a studio should be treated to create the most accurate sonic response are legion. But you know, it’s one thing when you’re talking about a ground-up build-out of a space purposely designed or remodeled as a recording studio or control room, where you have free rein to make changes to the structure of the room — and a budget for getting things done. It’s another thing entirely when you’re in the situation most project studios face: converting an existing room in a home into a serviceable — nay, great-sounding — studio, without spending a bank-load of bank.

With that in mind, we presented the following real-world challenge to four companies that specialize in acoustic treatment solutions — Auralex, MSR (StudioPanel), RealTraps, and Primacoustic — and to two studio designers — Russ Berger of Russ Berger Design Group, and John Storyk of Walters-Storyk Design Group. Each provided an acoustic treatment design for the room, along with an explanation of what went into their plan.

THE ROOM

Our Case Room: a spare bedroom located in a walkout basement, beneath a two-story house. There’s a major constraint to the treatment of the room, one most project studio owners face: We need to be able to return the room to a bedroom with minimal effort should the house ever be sold. Because of this, any acoustic treatment will need to be incorporated into the existing room. We can’t move walls or perform major construction/modifications. We can add built-ins and/or shelves, and hang treatments on walls and from the ceiling.

The room has smooth finished plaster walls and ceiling. It has a concrete floor originally covered with an example of the most gawdawful green carpet ever foisted on the 20th-century public. The carpet has been (thankfully) removed, revealing the bare cement floor beneath. The floor will be finished with either paint or concrete stain, then covered with an 8'x11' rug with a separate rubber carpet pad. There is an 11.5" deep soffit that runs around two sides of the ceiling, reducing the ceiling height in those areas from 99" to 87.5". One wall of the room has a 4" offset. We want to be able to take advantage of not being in a cave — the natural light and green backyard view from the windows are important to the “feel” of the room. Soundproofing the studio with regard to the outside world and the rest of the house isn’t an issue. All we’re concerned with is optimizing the sound within the room itself.

The studio will be used for composition and as a control room when editing, mixing, and mastering. The room will be used for some tracking of solo vocalists and instruments, acoustic guitar, hand percussion, and so on, but most actual miking/tracking will take place in another part of the basement, with this room serving as the control room. The studio will be used primarily for stereo monitoring, but will be used for some surround (5.1) production and monitoring.

Note that we asked the designers to focus on the acoustic treatments necessary for the room. When you’re planning your own studio, make budget allowances for HVAC, AC power and grounding, cable management, furniture, and other issues.

REALTRAPS

According to Ethan Winer, a primary feature of the RealTraps acoustic treatment solutions is minimal damage to the room from installation — the treatments can even be mounted to stands; whether those from RealTraps or basic microphone stands.

Ethan oriented the mix position so that it faces the room’s blank wall, and recommends placing the five monitors on stands to minimize reflections off desk/console surfaces. He suggests finding the ideal frequency-response placement for the speakers using ETF or similar analyzer software. When tracking in the back of the room, he recommends rolling the carpet away from that area for best results.

According the Winer, “It’s always best to have the loudspeakers fire the long way down the room because that puts you farther from the wall behind you where the low-frequency peaks and nulls are most severe. I defined the listening position at 38 percent of the way back in the room when measured from the front wall. This distance gives the best compromise of modal peaks and nulls, to get the response as flat as possible independent of bass trapping. The listening position is shown centered left to right, but in practice you’ll want to sit a few inches to either side — let’s say four to six inches off center. This gets your ears out of the width mode’s worst null, yet is not so far off-center it affects stereo imaging.

“The two biggest problems in all small rooms are the severely skewed low-frequency response and narrow-band modal ringing. Both of these are best solved by broadband absorption that’s effective to as low a frequency as possible. Then — unless the room has many bare reflecting surfaces — only the first-reflection points on the side walls and ceiling remain to be treated.

“For bass trapping I specified a mix of MondoTraps ($299.99 each) and MiniTraps ($199.99 each). MondoTraps are used in the four wall-wall corners, and MiniTraps go in the wall-ceiling corners. I specified MiniTraps there because they’re lighter and smaller than MondoTaps, and thus are easier to install, yet they still provide substantial absorption to as low as 40Hz. Since the left rear corner has a closet door, that MondoTrap will go on a RealTraps Stand ($79.99). I also added two HF MiniTraps ($199.99 each) on the rear wall to absorb those reflections because the wall is less than 10 feet behind the listening position. With such a short distance, without absorption those reflections would arrive less than 20 milliseconds from the original source and adversely affect imaging.

“For first-reflection control I used six MicroTraps ($139.99 each), with two on each side wall and two more overhead. If the room were used only for stereo you could get by with half as many MicroTraps. But with the addition of surround speakers there are more reflection points that must be treated. I specified MicroTraps for first reflections rather than HF MiniTraps because MicroTraps are smaller and lighter, yet they’re still plenty effective down to the lower midrange. First reflections are mainly a mid/high frequency issue, so MicroTraps are perfectly adequate and they cost a little less. Another pair of MicroTraps is then used over the tracking area to avoid floor-to-ceiling flutter echoes and ringing.”

PRIMACOUSTIC

The Primacoustic design kept the comfort of those working in the room as Priority One, while also keeping things cost-effective. According to Peter Janis, “Although we’ll control the major acoustical concerns, we won’t try to turn a simple rectangular room into a multi-million dollar studio. What we’ll do is create a space that’s reasonably neutral and will enable the end product to be played back with good results in a variety of rooms or spaces.

“All rooms suffer from the same problems. These include front-to-back and side-to-side flutter echo, strong primary reflections from adjacent walls and the ceiling, and of course excessive bass with resonant frequencies (standing waves) in the 77, 90, and 137Hz regions (based on the room dimensions).

“To treat these problems, we’ve opted for a London 15 Studio Kit ($850 list). This includes a Europa 83 flutter wall, two Orientique washboards, four Australis bass traps, and a Scandia scatter block. The London 15’s components combine to achieve the ‘live-end, dead-end’ (LEDE) concept. For this room, the kit has been supplemented with two additional Australis bass traps ($200 list) for a total of $1,050.

“To control front-to-back flutter echo and standing waves, the Europa 83 (‘1’ in the diagram) is placed on the front wall above the work surface. This 36"x 96" wall combines a deep anechoic wedge design along with solid blocks to allow the user to create a unique and distinctive look. The Europa also reduces rear reflections from the monitors. Powerful side reflections and wash are controlled with Orientique washboards (3). These 36"x36" panels help eliminate side-to-side standing waves. To control bass, six Australis bass traps (2) are employed. These are stacked to enhance performance and placed in the three available corners. Although the deep 12" corner-trap ‘solid block’ design provides excellent bass absorption, high frequencies are also absorbed. The ceiling above the control work surface is treated with a Cloud-9 ceiling kit. This completes the dead end treatment and results in a wider sweet spot and dramatically increased imaging.

“For the live end of the room, the London 15 kit employs scatter blocks called Scandia (4). These are placed on the back wall to reduce front-to-back scatter echo and work with the Europa to reduce standing waves and room resonance. This ‘soft diffusion’ provides an affordable alternative to diffusers by allowing some of the energy to reverberate back into the listening area while suppressing the rest.

“We’ve added items to the room that are helpful for acoustics and required as comforts. A couch will help absorb bass in the room while also eliminating flutter echo from the bottom part of the rear wall. A bookshelf below the window will provide diffusion and storage space.

“The soffits that run across the ceiling at the back and side have been left untreated; they’ll act as natural diffusers. If the room is too live, treating their front edge would be an easy add-on.

“In order to make installation and dismantling easier, we suggest backing kits. Glue the acoustic panels to the corrugated plastic panels, then mount to the walls or ceiling using finishing nails or tacks. This makes taking down the foam easy and doesn’t leave you with a drywall repair mess! The cost for three backing panel kits is $100.”

AURALEX

Jeff Szymanski of Auralex designed an acoustic treatment plan that manages the average reverb time in the untreated room. Szymanski says, “While reverb time isn’t the best acoustical guideline for small rooms, it was deemed to be useful for this room in the absence of strong reflection problems from any specific surfaces. The measured average reverb time in the room was about 0.45 seconds. This is roughly double what you’d typically want in a studio control room environment. However, since the room is to be used for recording as well as mixing, we have suggested roughly 22% coverage with TruTrap Genesis materials. This type of treatment will control the main problems in the room well without killing everything. The average reverb time should be reduced to roughly 0.35 seconds.

“At 50-60Hz and above, the treatments outlined in the design should control the low-frequency problems quite well. ‘Off-the-shelf’ treatments won’t sufficiently address the mode problems below 40-50Hz. For serious problems in this range (most notably build-ups in the 41-49Hz range), consider some larger custom traps (Auralex can help you design them), or you can try tweaking the response with some of the new room correction packages that are becoming available. The former is a better approach, but the latter could prove to be less cumbersome and less labor intensive (very low-frequency traps are challenging to build and take up a lot of space).

Referencing the numbered callouts in the diagram:

1. Two TruTraps mounted over the corners, centered at or slightly above ear level. Purpose: control low-frequency build-ups and cancellations in the room that originate in vertical corners.

2. One TruTrap mounted to the left wall, two mounted to the front wall, centered at or slightly above ear level. Purpose: minimize wall reflections and low-frequency anomalies.

3. Three TruTraps mounted to the back wall with two Q’Fusors mounted to the face of each TruPanel, centered at or slightly above ear level. Purpose: minimize low-frequency anomalies and diffuse high frequencies for a “live end” result. If surround mixing will predominant, the Q’Fusors are optional.

4. Three TruTraps mounted to the ceiling above the main mixing area. Purpose: minimize low-frequency cancellations/build-ups and high-frequency reflections. Two Q-Fusors can be mounted to each TruPanel if desired.

5. One TruTrap mounted to the right wall. The panel is turned 90 degrees and centered at ear level to control wall reflections.

6. Two Q’Fusors mounted to the door, centered at or slightly above ear level. Purpose: control reflections from door.

7. Heavy (min. 40oz./yard) curtains over the windows. The “fold” should be at least 4" deep.

8. The closet should be filled with insulation, clothes, or other porous material. Purpose: additional low- and high-frequency control. Experiment with the bi-fold doors closed and slightly open to determine best results.

The four TruTrap Genesis Systems required for this room have a total retail price of $1,316 ($329 each).

MSR StudioPanel

Control of reverb time across the frequency spectrum was the goal of the StudioPanel design. Evan Rieley of MSR Inc., manufacturers of the StudioPanel acoustic treatment kits, says, “Acoustic treatments were specified to reduce reflection decay time to averages suitable for a studio. All reflection energy should decay by 60dB within roughly 0.26 seconds for this volume of room (1,460 cubic feet). Decay time should be smooth across all frequencies; the devices in the StudioPanel kit cover the full frequency range to achieve this result.

“It’s important not to over-absorb sound in the studio. StudioPanel Diffusers break up reflections and scatter the sound energy; this maintains ‘liveness’ and improves the surround field.

“The first reflections from speakers (‘1’ in the diagram) to listener position should be attenuated by 15dB or more or they will negatively affect frequency response and imaging. This can be achieved using either absorption or diffusion.

“The listener position shouldn’t be located in places of standing wave dips or peaks. A simple method for finding the ideal position is to multiply the length of the room by 0.55 and place the listener there.

“Four subwoofers (2) correctly positioned in a room can cancel standing wave errors producing very smooth bass response. (See AES paper #5602 by Todd Welti for more info.) The four subs play the same signal and are in-phase. The signal is still considered 5.1; the levels of the four subs are adjusted to play at reference loudness.

“Absorber panels (3), which provide absorption down to 250Hz, are placed around the room to break up reflections. We also included absorber panels in the closet to absorb noise produced by the computer, hard drives, and outboard gear fans. The Absorbers are alternated with Diffusors (4) on the studio walls for even dispersion down to 500Hz.

“Bass resonances from standing waves are reduced by Bazorbers (5), which provide Helmholtz and tympanic absorption from 100–300Hz, and SpringTraps (6), which provide resonant bass trapping from 30–100Hz. These will reduce the ‘boom’ of the room creating an accurate place to hear bass in your mixes.

“Two CloudPanels (7), mounted to the ceiling above the mix position, break up floor-to-ceiling reflections, with absorption down to 250 Hz.

“We recommend covering the front window and rear closet doors with fairly heavy velour drape material (8), 32oz./yard, 62" wide by 80" tall. This will control reflections while maintaining the ability to use the window and doors. Draw the drapes for critical listening. The side window should be covered with 3/4” plywood before covering with acoustic treatments.

“The StudioPanel kit will also improve the quality of sound recorded in the studio. By controlling the decay time, smoothing the bass response, treating specular reflections and flutter echoes, and maintaining some diffuse ambience in the space, tracks will have improved sound and less ‘room signature.’”

The Walters-Storyk Design Group went for an overall room design. John Storyk says, “There are a number points to consider for a design solution, starting with the user’s orientation in the room. Most people will want to face the large window. More often than not, this is the best location for a large piece of glass with a great view. (We assume a view!) Although I don’t like entering in the rear of a room, I feel facing the large window is the way to go. Once this has been decided, we need to look at the workflow/furniture.

“We’ve assumed a typical workstation — a ‘U’-shaped workflow environment. We also assume nearfield monitoring. Whether there’s a small console, a control surface, or combination of those options isn’t critical in creating the acoustic environment.

“Acoustically, low frequencies are the most difficult issue to deal with in small rooms. No matter how mid- and high-frequency reflections are dealt with, low frequency is an issue all to itself and strictly a function of three considerations: listening position, speaker position, and room ratios.

“We use software programs to determine the critical modal anomalies for the room. In this example, the room ratios aren’t perfect, and they can’t be changed. We’ll add prefabricated low-frequency absorbers to the front corners, as well as above a suspended ceiling cloud. There are a few companies currently manufacturing these units (RPG, VPR, Pawel Absorbers from Switzerland, etc.). Another option is to fabricate custom low-frequency membrane absorbers (a bit tricky and more costly).

“Generally mid-/high-frequency analysis isn’t that difficult. Ray tracing or reflection control analysis generates clear suggestions for the positioning of treatments. For this room, some side wall treatments augmented by broadband diffusion in the rear will do the trick. The rear room diffusion will spread out the ‘sweet spot’ a bit for the listener and improve stereo focusing. The ceiling cloud will handle mid- and high-frequency control for the vertical dimension.

“Here’s how we implement the basic concepts architecturally: The rear wall diffusors could be simply set on floor — kind of like monolithic blocks. These will also help to define the stereo listening environment and create two small alcoves, which could be used as ‘semi-iso’ areas for recording.

“The ceiling cloud can be constructed as a wood or metal frame covered with fabric and filled with mid-density insulation or acoustic foam. The cloud would be suspended and might also be multi-purposed to accommodate task lighting (small recessed spots or track). Above the cloud would be the remaining low-frequency absorbers.

Put the speakers on stands — definitely not on the console bridge. Console or work desk reflections are a common problem in small rooms and we do not want them! ‰

“The more I think about the rug, the less I’m sure we need it. This depends a little bit on the extent of the ceiling cloud. The final decision would depend on personal taste. Some users are more comfortable working on carpet. Others don’t like rolling chairs, etc., on a rug.

“Finally, get a great chair — this is going to be your home for lots of hours!”

The Russ Berger Design Group prioritized their design on several levels. Richard Schrag, a principal of the RBDG, elaborates: “The monitoring environment should be set up with the operator facing the blank wall — that is, with the door on the operator’s left.

“As is, the room volume and ratios are far from ideal. Since we aren’t allowed to consider options that might make the volume greater, the best we can do is adjust the room dimensions to optimize the modal response. The biggest problem with the existing room ratios is a fairly wide hole around 160Hz. The front side walls could be splayed to alter the width in this portion of the room.

“Locate the mix position around 6'-6" off the front wall, centered in the room. Speakers should be kept at least 2' off the front wall, and around 3' from the side walls. This puts the monitors pretty close to the mix position, but avoids some nasty problems that would crop up if they were closer to the boundaries.

“Put absorption (4–6" thick, medium-density glass- or organic-fiber core) in the front corners of the room, about 3' out from the corner in each direction, full height. This not only prevents corner reflections back into the mix position, it also helps control mid-bass resonances in the room. Avoid specular reflections and scattering from the surfaces forward of the mix position.

“Suspend an absorptive ceiling “cloud” (2" thick, medium-density glass- or organic-fiber core over 2–4" air space) above the front 2/3 of the room to help control reflections from the hard surface overhead.

“On the remainder of the front wall, and on the side walls back to the door and window, put absorption at 2" to 3" thick from just below seated head height (approximately 3’ above the floor) to just above standing head height (around 7'). This will control reflections from the near surfaces back into the mix position.

“Cover the rear wall with a combination of mid-band diffusion in the center (using either manufactured treatments or bookshelves) and absorption with a deep air cavity (around 12" thick) toward the corners. The bad news is that this treatment should cover the small window. The good news is that the rear wall treatment can be used to visually eliminate the 4" offset in the rear wall.

“Make a removable, hinged, or sliding panel to cover approximately half of the large window for sessions when accurate monitoring is particularly critical. Otherwise, there will be a direct reflection from the left monitor directly back to the mix position.

“Use the closet to house the noisier equipment (CPUs, hard drives, power supplies, power amplifiers), and make it a bass trap. Replace the doors with wooden frames having 2" low-density absorption over pegboard, then line the interior of the closet with 4" absorption. This will reduce the equipment noise in the room, and at the same time terminate one of the room diagonals with absorption that’s effective below 200Hz.

“Suspend a combination of absorption and diffusion above the remaining 1/3 of the ceiling. This will help make the rear portion of the room more uniform when the room is used for recording.

“Since the operator will end up between the door and the window, cover the door with high-frequency diffusion to eliminate flutter echo.

“So far, we haven’t talked at all about the budget for these treatments or what they look like. If appearance isn’t that critical, reasonable acoustical performance could be obtained by mixing and matching off-the-shelf products. On the other end of the spectrum, a completely custom approach to the room’s aesthetic could incorporate specifically tuned acoustical treatments into a well-balanced finished appearance, tailored to your own tastes.”

THE WRAP

One room, six different designs. Of interest are the many differences — and similarities — between them. Which will work best? The answer depends on the final budget and other factors, not least of which is personal taste. We’ll show you how we ended up treating the room, as well as an “after” frequency response analysis in an upcoming issue.

So what are you waiting for? Improving the acoustics in your studio is the fastest way to improve your recordings and mixes. The better your studio sounds, the better your mixes will translate to other rooms and systems.

Most (if not all) of the principles used by the designers for their plans here can be applied to improving the acoustics in any studio or recording space. With just a small monetary investment, and slightly bigger labor investment, you can have a great space for creating music. Get busy!