Intelligent Studio Monitors

Jun 1, 2008 12:00 PM, By Michael Cooper

SELF-ALIGNING SYSTEMS PROMISE THE WORLD WILL BE FLAT

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JBL LSR4328P

JBL LSR4328P

Every listening space — whether a state-of-the-art control room or a simple basement/bedroom studio setup — has a problem: the laws of physics. As soon as you enclose a space with walls, a ceiling and a floor, the monitoring system's frequency response goes out the window.

There's no avoiding this hazard completely (although capable studio design and construction can minimize the damage to the point where it becomes fairly negligible). The presence of parallel room boundaries, such as facing walls or opposing floor and ceiling, causes the build-up and nulling of SPLs at certain frequencies within a room. These peaks and dips, called “room modes,” dramatically skew the frequency response at some places in the room while having little effect at others.

Speaker-boundary effects — caused by the acoustic coupling of speakers to nearby walls, tabletops, shelves or other surfaces — also wreak havoc by arbitrarily boosting bass frequencies. And sound emanating from monitors invariably gets diffracted when it hits the edges of nearby gear and furniture, resulting in comb filtering. What's worse, these aberrations in frequency response are different for every room and monitor setup, precluding any one-size-fits-all solution.

Splayed walls, vaulted ceilings and various acoustic products (bass traps, diffusers and polycylindrical absorbers) can greatly mitigate many of these problems, but not everybody can afford them. There's also a limit to what acoustic materials can fix. Truth be told, most of us work in rooms that aren't flat. Adding to these problems are manufacturing tolerances. Those little plus and minus signs in the frequency response spec show you that due to minute variances in materials and construction techniques, each monitor will have a slightly different inherent frequency response than the others.

Many studio owners use software and outboard EQs to help flatten their monitoring system's frequency response. Analysis software such as Metric Halo SpectraFoo or EAW's Smaart can be used to identify the worst room modes (those with the deepest peaks or troughs in response) and speaker-boundary effects for your particular setup. Parametric EQs — placed in the monitoring path — can then be used to boost or cut at frequencies affected by the room modes to bring the response closer to flat. (For reasons too complicated to detail here, only room modes below roughly 200 Hz need to, or should be, treated.) Shelving filters can also be used to roll off any unwanted bass boost caused by speaker-boundary effects.

Recently, a number of monitor manufacturers have bundled analysis software with the onboard digital signal processing in their monitors to accomplish what outboard EQ and third-party software do — and, in some cases, do them much better. Such bundled software essentially measures deviations from linear response for your system — monitors and room — followed by corrective equalization to help flatten the overall response.

To keep the process as simple as possible, some systems automate the routine. The user typically sets up a microphone in the control room, and after a few button-presses/mouse-clicks, the software takes over, automatically handling the rest. There's no need for you to set up test gear, analyze data and make manual adjustments to EQs; the monitors are intelligent enough to align themselves.

This article examines the current crop of active, self-aligning studio monitors. All the models detailed here operate with included or optional analysis software, along with proprietary automated digital processing. To keep the article focused on the cutting edge, monitors without automatic alignment are not included. Those that simply offer the same switched equalization presets for all production units or don't use proprietary analysis software are not covered, although the attached “Honorable Mentions” sidebar on page 44 offers a brief discussion of such.

GREAT EXPECTATIONS

Before we dive into the details, we should mention what you can expect from an intelligent monitoring system. Some intelligent systems choose to treat only peaks and not dips in response. In such cases, the argument is that boosting frequencies where room modes cause notches at the reference position is ineffective and will eat up precious system headroom. I believe you can treat notches with EQ boost and get excellent results — if you know what you're doing. However, most self-aligning systems are designed so that even a novice can achieve great results, a reasonable approach that can provide a significant improvement in system response.

The number and type of filters (e.g., parametric or shelving) included in an intelligent system partly determine how powerful and effective it will be. The quality of the filters plays an enormous role, too; a noisy filter that causes phase shifting does more damage than good. But don't overlook traditional considerations such as driver size and power specs when shopping. Even the most powerful DSP can't make a tiny speaker produce enough bass to drive the neighbors nuts. Check out the chart below for these and other important buying considerations.

It's also important to realize that room modes behave differently at various positions in your room. A room mode that causes a huge dip in response at the mix position may have little or no effect a couple feet away and cause the opposite effect — a huge peak — where your clients are sitting. Therefore, any corrective EQ determined from test measurements taken at your listening position will only fix the frequency response at that location.

Here's where networked systems really shine: letting the user control all connected monitors from one position — optimally, the listening position. Networked systems typically allow users to store/recall different EQ setups tweaked for various listening positions throughout the room. By toggling through these presets, the producer and clients can, in turn, hear a spectral balance that's approximately the same as that which the mix engineer hears.

Additionally, networked systems often let the user balance one monitor's level with respect to another's, without moving from the sweet spot. The network may also permit tweaking an included subwoofer's phase to achieve optimal bass response with satellite monitors. Rather than making an adjustment at the subwoofer, it makes sense to do this under network control from your listening position, where you'll be making decisions about your mixes' bass perspective.

Attentive readers will notice I haven't talked about equalization fixes for comb filtering. This is because EQ can't correct this. Acoustic diffusers are usually used to mitigate comb filtering, but ergonomics at the mix position severely limits their application for combating near-field diffractive effects. Simply put, you can't move your mixer's faders if there are diffusers on top of them! That said, Equator Audio Research has devised a time-based solution for comb filtering.






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