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Earthworks Sigma 6.2
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Object lesson #19: Great sounding speakers aren’t accurate monitors, but here’s why we need both.

Issue #7
December 22, 2003

A few columns back, I did a hands-on review of the Earthworks QTC30 omnidirectional microphones and I raved about them. When evaluating a set of exceptional mics — or any other audio for that matter — you want to hear the final recordings played back through several sets of monitors to really see how the product performs on various systems. One of the monitors I used were Earthworks’ own Sigma 6.2s, but I’ll get back to this in a minute.
Oddly enough, the first time I was exposed to the concept of how much a particular set of monitors, coupled with room acoustics, could color a sound was when Electronic Musician did a review of my original sample library for the Akai S1000. The reviewer, Geary Yelton, admitted to me that he wasn’t particularly impressed when he first auditioned the sounds at a friend’s studio, but when he brought them back into his own home studio, he was blown away. Not surprisingly, he had exactly the same monitors in his studio as I had in mine: Tannoy PBM8s. End result? My sounds earned the tag “the best samples money can buy.”

Why the big difference?

Well, you can start with all the variables involved with being in an environment you’re unfamiliar with. Most small home and project studios are set up in an extra bedroom, a garage or maybe a basement. Very few are capable of delivering audio without major frequency anomalies (thin bass, boomy midrange and so forth). Thankfully, our ears will actually adapt to the sonics in a poor room, so most of us are usually able to create good mixes once we understand the shortcomings of our particular setups.
In true pro studios, huge amounts of money are spent not just on gear, but also creating a workspace that is not going to degrade the audio signal: Big bucks go into designing these environments, and all the top installations are tuned using RTA (Real Time Analysis) to make certain recording engineers are going to hear the audio and not the room.
Back when I first started recording in my own home studio with the classic TEAC 3340, there was no such thing as the Internet, and no trade magazines like EQ, Mix or EM. So very few of us understood that the acoustics in our listening environments played a big part in sound quality. Today, there are companies like Auralex that specialize in creating products that do nothing more than help correct all the myriad problems that plague a typical home studio or home theater setup.

Okay, so we have learned that our listening environment can have a significant effect on our audio. To lessen the influence of the room, we want to use nearfield monitors when mixing. Some nearfields are best used just a few feet away from the listening position, while others may produce exceptional results when used anywhere from two to maybe six feet away. Normally, in my own studio, I monitor very close to the speakers— maybe a bit over two feet. After unpacking the hefty Earthworks Sigma 6.2s, I checked the documentation, which suggests that these monitors are best used at distances of three feet out to a maximum of nine feet.

Deep, heavy and radical

Since the Sigmas measure almost twice as deep as my Tannoys, I moved everything around so that I sat about four feet from the monitors, which were set about a foot away from the back wall and at least four feet from the adjoining walls. Naturally, the first thing that struck me about these speakers was their weight (at 32 pounds, they’re more than twice as heavy as my Tannoys) and their radical design, which was really no surprise, as Earthworks products almost never go with traditional designs unless there’s a darn good reason. Check out the photos and you’ll see what I mean, but the unusual design is also quite handsome, at least in my opinion.

The tweeter is actually mounted onto a front plate or flange, rather than within the enclosure. From the photo you’ll see that the cabinet features a triple-stepped front baffle, with the bottom section housing the woofer, which is tilted upwards at a slight angle. Above that and recessed by about an inch is the plate-mounted tweeter. Finally, a wide rectangular port reflex loads the woofer (and also provides an excellent handle when lifting the hefty Sigma 6.2s). Incidentally, both drivers are built by Vifa, a company based out of Denmark with a reputation for exceptional quality. The unusual design helps deliver on the promise of time accurate soundfield reproduction.

High frequencies are fast!

It’s a well known fact that high frequencies move faster than low frequencies, so arranging the woofer, tweeter and bass reflex port in this specific manner helps time align all the elements to eliminate the “smearing” that plagues many typical speaker designs. By tilting the woofer upwards, its upper midrange arrives at our ears at the same time as the tweeter’s high frequencies, which is part of the reason that the Sigma 6.2 system is so remarkably accurate. Every cabinet edge on the monitor has a 1-inch radius to minimize diffractive effects.

The tweeter is driven by a 1-inch voice coil, and a phase plug, located in the center of the tweeter, reduces the crossover of acoustic energy from one side to the other. The tweeter is also slightly inset in its beveled surround, forming a very shallow horn. Looking at a pair of Sigma 6.2s, you’d see that each woofer and tweeter is mounted slightly off-center. Sigma 6.2s are sold as closely matched pairs, so that one unit’s drivers are offset slightly to the left of center and the other unit offset slightly to the right. Earthworks specifies no correct “left” and “right” speaker assignments, so we’re left to our own devices here. Personally, I could not hear any difference after swapping out the left and right speakers.

But enough about the design, you want to know how they sound. Well, right from the start of this column, you probably noticed that I am talking about two distinct features: Great sound and superb accuracy. Most of today’s best-selling home theater speakers are designed to sound great, with a frequency curve that is quite often far from flat. I personally have a set of Infinity towers in my home theater, and while the average person who gets my DTS-encoded “Lord of the Rings” DVD demo are floored by the sound (which is augmented by a room-shaking subwoofer), it’s a system that’s not particularly accurate. The same could be said about most any of today’s typical cineplex theaters unless they are THX compliant (and very few are).

Conversely, the Earthworks Sigma 6.2 system is built to deliver the most accurate sound possible. So when you hear a great recording, you are in essence hearing the performance, not the speaker. The best way to put it is that the very best audio components do not color the sound in any way. This is true of the Earthworks microphones, as well as their preamps and now, the Sigma 6.2 monitors. Much of today’s music — with its radical EQ and hyper-processing — is engineered to be anything but accurate. The musicians who are creating that music are probably not going to be interested in a set of Sigma 6.2s, but anyone recording music that features real acoustic instruments and vocals will immediately be knocked out by their sound, which is amazingly detailed.

Side-to-side separation AND front to back imaging

In my previous column on the Earthworks QTC30 microphones, I mentioned several sessions I had done at Florida State University, recording a Dvorak string quartet, as well as a viola recital (with piano accompaniment) and several three-piece ensembles. Listening to these recordings on the Sigma 6.2 system is truly the closest you’ll ever come to hearing the sound of the actual performances. The string quartet (one of my longtime favorites) is particularly sweet, and the viola pieces, in particular Grainger’s “Carol” which begins with a wonderful melody on the lowest two strings, are astonishing in their realism. Naturally, when I am auditioning any monitors, there are many favorite recordings that I immediately turn to, like almost anything by Pat Metheny, Bonnie Raitt’s “Luck of the Draw” and The Chieftains’ monumental “The Wide World Over” (I dare you to listen to their collaboration with Joni Mitchell on “The Magdalene Laundries” or with Van Morrison on "Shenandoah" without getting chills). The Jerry Goldsmith soundtrack to “First Knight” with its huge orchestral palette that includes bells and glockenspiel is a great test of any speaker system, as is Howard Shore’s “Fellowship of the Rings” soundtrack recording which closes with Enya’s haunting “May It Be.”

All of these came across with startling clarity on the Sigma 6.2s, which reveal the softer “inner voicings” of the material that are often lost on a lesser system. In particular vocals have a stunning realism I have never experienced to this degree. I also have several high resolution 24-bit recordings, including Eric Clapton’s “Reptile” as well as his collaboration with B.B. King on “Riding with the King.” Honestly, you really must have monitors of this quality to truly appreciate the difference between 16-bit and 24-bit source material. Aside from their accuracy and detailed reproduction, I was also surprised by their depth and the spaciousness of the stereo field, which means that even two channel recordings maintain some feeling of the recording environment (i.e. a concert hall on classical recordings or orchestral soundtracks). Most mid- to high-end monitors have good side-to-side separation, but lack front-to-back imaging. The Sigma 6.2 system actually delivers both.

Okay, if there’s anything a person might possibly quibble about, it’s the Sigmas’ lack of really low bass. That observation might be made because many of today’s speaker systems have a slight bump in the low end, particularly in to 60-100Hz range which make them appear to have more bass response, but the Sigmas are only down 2dB at 40Hz! The low E on a bass guitar is 42Hz, so that’s still comfortably in their range, and you can clearly hear a low E on recordings that go that low. Using a test CD, a 42Hz sine wave is quite audible, but you have to remember that our ears are more sensitive to the higher frequencies, so that might make it seem that there is less bass. I personally like just a bit more of a solid thump in the lows, so I have a small subwoofer in my studio I can switch in. But that’s simply a matter of taste. When mixing a critical recording, I'd never consider using the sub.
Earthworks also gives the Sigma 6.2’s sensitivity as 87dB (one watt@one meter), but I heard no difference in perceivable volume when switching between my 90dB Tannoys using a Yamaha 120-watt per channel amp. All of which means these babies can play loud enough with even modest amplifiers to damage our ears.

To cut to the chase, I’ll go on record as saying the Earthworks Sigma 6.2 monitors are the best, most accurate speakers I have ever used. That’s not to say you can’t get a great sounding speaker for less money, and in fact, there are several powered systems that carry lower list prices than the Sigma’s $3333 MSRP. It’s all in the way you prioritize your audio. To me, it doesn’t make sense to use an expensive set of mics and a premium preamp or console and then skimp on your monitors. If you’re looking for a system that delivers the ultimate in superbly detailed, highly accurate audio you seriously need to check out these monitors!

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