Nov 1, 1994 6:52 PM, By Bob Hodas

ON CLOSE-FIELD MONITORING SYSTEMS

As an independent recording engineer, I have been using near-field monitors for the past 14 years. The decision to purchase my own near-fields was made in 1980 after a disastrous recording project in Japan. Studio selection was handled by the record company, and everything was set in stone when I walked off the plane. Three separate facilities were used for tracking, overdubs and mixing. All three sounded completely different because they had different monitors and acoustic designers. I brought along a tape I was familiar with and tried to get a reference in each room. Well, this turned out to be quite difficult, especially in the mix room.

All the staff engineers were quite proud of the their rooms, and I was uncomfortable suggesting that there were acoustical problems. One studio’s staff was absolutely beaming because they had not paid a design fee, even though this was obviously a room done by a well-known designer. They had taken the design drawn up for their European parent company and used it for their own room. The only problem was that the Japanese room was much smaller and they had simply shrunk the design dimensions using a ratio (not to mention that they installed different monitors). I didn’t have the heart to tell them that it doesn’t work that way. The coup de grace was at the mastering studio, whose dimensions were a perfect cube. Standing waves were a nightmare.

Upon my return, I purchased a set of speakers that was to become my reference standard no matter where I went. At this point, I would like to give credit where credit is due for those of you that don’t know your audio Hall of Fame history. Ed Long’s Calibration Systems in Oakland, Calif., holds the trademark for the term "near-field monitor," as well as other industry-sweeping innovations such as Time Align. Out of respect for Long, engineers should know that today, the term “near-field” has become synonymous with close-field monitor systems just like Kleenex is synonymous with tissue paper.

Near-fields eventually became a standard in the industry, as staff engineers positions vanished and the independents roamed. Engineers found themselves fooled by in-house monitor systems that were inaccurate or not properly maintained. I must admit that having a standard helped me to make better records, but I still found that my speakers could sound different in a variety of studios. This history led me into the field of room measurement, as I had a desire to quantify exactly what I was hearing, all in the quest of making a better record.

I firmly believe in large room/transducer interface designs. Large soffitt-mounted monitors can sound fantastic and at the same time be more fun to work on than small speakers. If properly designed, they may also be more accurate than untuned console-top speakers. I have several room-voiding clients who are very fastidious and proud of their monitoring environments. They keep their rooms regularly voiced, and they recone woofers and replace diaphragms on a regular schedule.

There seems to be a pervasive belief that if you use a console-top speaker, you will not be affected by the control room acoustics and will get a more accurate frequency response. This line of thinking also has led many people to believe that home studios can get away without acoustical planning or treatment because the speakers are in your face. In a word, wrong. Close-field monitors can be accurate only if care is taken in the placement of the speakers and room issues are not ignored.

MEASUREMENT METHODOLOGY
The Meyer SIM System II, which I used for these tests, allows the gathering of large amounts of information in real time, which aids in diagnosing problems quickly. In one screen, a room response (pre- and post-EQ) is displayed, along with the EQ curve applied to the room and an analysis of the system coherence. Other screens display room and phase response in real time. Room reflections may be identified, and time alignment of components is clearly displayed. The system gathers information at 1/24-octave resolution (245 frequencies, 8 Hz to 22 kHz), which provides the ability to look deep into a room. Test signals include impulses, tones, noise—even music may be used.

There are other parameters in addition to frequency response and phase. One such parameter is coherence, a 245-point signal-to-noise ratio (on a per-frequency basis) of the system under analysis. It compares the test signal source to the signal received at the microphone. This can show direct vs. reflected sound, as well as distortion in the system. The Delay Finder displays an impulse response that shows time alignment and room reflections.

Near-fields will not always display the exact same problems as the soffitted speakers. Position in the room can make a big difference. I have solved certain problems by moving speakers a mere six inches. The important point is that the room acoustics do not affect the near-fields, and you cannot expect to avoid a room problem just by putting a speaker up close to your face.

These low-end anomalies are usually related to the dimensions of the room, but sometimes, they can be diaphragmatic, as well. One example of a diaphragmatic problem is a non-reinforced wall that vibrates at a specific frequency and cancels that frequency out of the room. What are the solutions to these problems? There are two ways to go about it. I often recommend contacting an acoustician once the problem has been identified. You need an expert to give you cost-effective solutions. Solutions may include such things as bass traps, resonators, diffusors or even moving walls. Some dimensional problems and placement loading problems may also be cost-effectively solved using a minimum-phase parametric equalizer. You need a minimum-phase EQ because the room problems described here are minimum-phase phenomena and must be corrected as such. These solutions are also not necessarily mutually exclusive. The combination of acoustic solutions combined with judicious use of a high-quality, minimum-phase EQ can produce stellar results.

Commercial studios often address their low-end problems with acoustics and EQ. Many still have some problems, but the majority of significant problems I have seen have been in project studios. Because project studios are often in homes, they share certain dimensional restrictions, such as an 8-foot ceiling height. Many small rooms suffer from an abundance of 150 to 300 Hz. The main signature that seems to proliferate in the project studio is modes that make the low end look like the Alps.

What about adding home stereo subwoofers to near-fields with the expectation that all low-end problems will be solved? I have seen several subwoofers where the crossover point does not meet the manufacturer’s specification. This can cause some significant problems.

Pardon my soapbox, but don’t think you can open a mastering room just because you can buy cheap digital mastering programs—especially if you don’t pay attention to room response! There is a lot to be said for relying on an expert’s ears and abilities in a room where many records have been mastered.

Care and attention need to be taken when setting up any listening environment, whether it is an existing professional control room or a new project studio. I hope the information above will dispel some myths and help you to make better records.