Recording - January 2013 - 43

intended for bookshelf-sized home stereo systems. Within a few years, however, use by engineers such as Bob Clearmountain propelled the simple speaker to become one of the most popular monitors of all time. Why did the NS-10M become king of the nearfields? Use by famous mixers helped create the mythology that if a mix sounded good on NS-10Ms, it would sound good anywhere. Is there truth to this notion? It depends on whom you talk to; many love the little white-coned loudspeakers, but just as many hate them. True, NS-10Ms are far from the most pleasing speaker out there. Lacking bass, and harsh in the midrange, they would not be your first choice for daily listening. Thus the sound quality of NS10Ms becomes a double-edged sword. On one hand, mixing on them can be difficult and not necessarily pleasurable. On the other hand, the effort required to make a song sound good on NS-10Ms seems to pay off in wellbalanced mixes that translate effectively to other systems. Hyperbole aside, a few technical features make the NS-10M a worthy studio monitor. The harsh midrange, centered in the crossover zone between the woofer and tweeter, falls right in the range of our ear’s greatest sensitivity. This forces an engineer to labor towards clean and smooth mids, which in turn helps mixes created on NS-10Ms sound better on harsh loudspeakers in the real world. Another technical advantage of the NS10M is its lack of porting. To understand this though, I must first explain some speaker design basics. Sealed or Ported? The NS-10M speaker cabinet is completely sealed. Known as infinite baffle, sealed loudspeaker designs have significant shortcomings. One disadvantage is that infinite baffle boxes are inefficient with amplifier power. Since energy can only radiate from the front of the speaker, fifty percent of the sound generated is lost. This waste occurs because drivers fire both forwards and backwards. The forward sound radiates into the listening space but the rear energy gets stuck in the sealed enclosure. Furthermore, when the woofer moves backwards, air within the box compresses. This creates a sort of “spring” that fights against the driver’s movement, requiring extra amp power to compensate. A couple of solutions exist to address the inefficiencies of sealed cabinets. One technique is to remove the back of the enclosure completely. This method increases overall loudness but has a serious drawback. Rear energy, opposite in polarity to that produced at the front of the speaker, exits the rear of the cabinet, diffracts (bends) around the sides, and partially cancels the frontfiring sound. This phase cancellation is problematic in low frequencies only, and thus open-back cabinets are only popular in guitar amp designs where low-bass energy is unnecessary. In contrast, you’ll never see an open-back bass amp. The next solution to the woes of infinite baffle enclosures is porting. Ported cabinets, also known as vented, or bass reflex, have one or more holes somewhere in the enclosure to let the driver’s rear energy escape. The ports, whose dimensions and location are precisely calculated, are tuned so that sound existing through them is delayed by specific travel time. This “tuning” ensures that energy escaping the hole is exactly one cycle (360˚) out of phase at a defined bass frequency. Sound from the port thus sums with the forward-firing energy and bass reinforcement occurs. Without porting, bass from a sealed infinite baffle box rolls off gently. With porting, low frequency response is extended, and bass is bigger and lower.

There Is No Such Thing As A Free Punch Bass reflex enclosures have long been popular for all types of loudspeakers, and studio monitors are no exception. Why then are NS-10Ms not ported? How then did a monitor with limited bass response get so popular? The answers to these questions are, like everything else involving phase, complex. Bass reflex enclosures, although offering extended bass, have a dark little secret. As mentioned, ports reinforce low frequencies by delaying the exit of rear energy until it is one cycle late. While this enables bigger bass through phase summation, it also means that some of the sound produced by the speaker is late in time. A sometimes-audible side effect of this is that some low frequencies linger for a short duration after a sound has stopped. The resultant ringing can affect the tightness of kick drums and other low-frequency transients. With bass smeared over time, the lowest frequencies can be less punchy and articulate. Also, a port’s bass boost is narrow-band only. This means that energy slightly higher than the resonant frequency suffers from phase cancellation and thus higher frequency response is somewhat uneven. More importantly, energy below the resonant frequency sees dramatic cancellation and response rolls off dramatically. While ported boxes allow extended low frequencies, they do not produce the lowest lows at all.

Rob Chiarelli (finalmix.com) has both soffited monitors and Yamaha NS-10M speakers in his mix room.
Getting back to NS-10Ms, the fact that they are sealed means that energy below 100 Hz gradually diminishes in amplitude. This makes the speakers bass-light, and while this may be a negative, the tradeoff is a lack of time smearing and a smooth frequency response curve. These attributes mean that NS-10Ms are not exaggerated and do a good job of representing a mix in a neutral manner. This inevitably contributed to the reputation that mixes made on NS-10Ms translate effectively to other systems. Conversely, these traits mean that a pair of NS-10Ms should be used alongside a bigger and bassier mains system. With the bass-light nature of NS-10Ms in mind, I want to conclude with one of the few truths in studio monitoring. As awesome as your monitors may be, you definitely need more than one pair. No one set of monitors represents every listening scenario. This is why pro studios offer mains, minis, and nearfields. Also, you’ll want to add to your arsenal a well-known pair of headphones, some cheesy earbuds, an ’80s boom box, and a trusted car stereo. These resources together will give you a fighting chance of making a mix that translates anywhere. Need to know what the track sounds like in a dance club? Check the mix on the mains. Wondering if the mix bumps on the subway? Use the earbuds. Curious if you can hear the vocal on grandma’s TV? Grab the minis. Yes, ultimately most of your mix time will probably be spent on nearfields, but variety is essential. Eric Ferguson (ferguson@recordingmag.com) spent a dozen years as a freelance audio engineer in Los Angeles, and is now on the faculty of the New England School of Communications (NESCOM) in Bangor, ME.
RECORDING January 2013

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Recording - January 2013

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