Earthworks Sigma 6.2 Time-Coherent Passive Studio Monitor
By Mitch Gallagher (mgallagher@musicplayer.com)

Over the past few months I've been in the enviable position of evaluating and reviewing a number of new studio monitor designs. And each of those speakers has had its strengths and limitations; it's been very interesting to compare mixes and recordings on them. Through it all, I've been anxious to get my hands on the Earthworks Sigma 6.2 speakers; I'd heard them at the fall AES show in New York, and had been quite impressed with them. I finally had my chance; here's what I found.

OVERVIEW

These are big, heavy speakers - especially for a 6.5-inch woofer design. Fortunately, the large rectangular port at the top of the cabinet makes a convenient carrying handle. The cabinets are made of one-inch MDF, and are resonance-free - you can rap on the heavily damped cabinet with your knuckles, and all you'll be rewarded with is a tight tap; no ringing. The manufacturer specs the cabinet resonant frequency at 40hz.

The cabinets have a sort of 'tiered" shape, with the woofer mounted on a slightly angled baffle. The tweeter rides in a sliding plate on the level above this, and the aforementioned port tops the cabinet at the third level. Earthworks says that this cabinet design is critical for achieving time-coherent audio from the two drivers and the port. On the downside, both cabinets had some minor wood-working and finish flaws, perhaps understandable in handmade speakers, but nonetheless troubling given the price of these monitors. (Earthworks assures me that they have corrected these problems for future production runs.)

But there's more to the design than just time-coherency. Both driver are offset from center to minimize boundary effect in any direction, and the cabinet is optimized to throw the sound only in the forward direction.

The speakers are shipped as a hand-matched pair, with the two woofers and the two tweeters in the pair matched and with each crossover custom-tuned to its corresponding driver.

The rear of the cabinets feature very cool gold-plated WBT-brand binding posts, which are covered with clear plastic casings, as well as gold-plated Speakon connectors. The binding posts have big holes for accepting large-guage speaker wire.

Earthworks says that the Sigmas were designed to present an easy-to-drive uniform load. I tested them with a 9505 amplifier provided by Hafler, and found the system to sound unstrained even at loud volumes.

THE SOUND

In my room, I ended up placing the Sigma 6.2's a bit further away than my regular monitors - 4-6 feet rather than 3-4 feet seemed to work better for low-end response and for imaging.

If I had to characterize the "sound" of the Sigma's, I'd say that they have some things in common with the Genelec family of speakers - but this is a very broad and, in some way, a completely inaccurate characterization. Some things sounded almost the same when played on the Sigma's and my Genelec 1030a's. For example, Marc Cohn's "Healing Hands" reveals a very similar tonality. But other reference tracks sounded very different; it was hard to pin down exactly what the differences were and what was causing them in the source material.

One thing jumped out immediately; These speakers offer outstanding imaging. Since the tweeters are offset from center, I tried them with the tweeters both in and out. Both sounded fine, but I preferred the tweeters on the outside for the slightly wider stereo field this produced. Because imaging is so wide and stable, it's easy to hear things panned in the middle such as lead vocals, kick, and bass. It was likewise a simple matter to pinpoint the location of tracks that weren't panned hard left or right.

The low end these cabinets put out is simply stunning - I was surprised at how much, how solid, and how deep the bass was coming from the 6.5-inch monitors.

The Sigma's aren't my favorite monitors for heavy rock; the music doesn't seem to "gel" as well as I'd like. It's hard to get it to sound like a cohesive hole. The revealing mids and highs also make the Sigma's somewhat harsh sounding with this type of music.

By contrast, these monitors love well recorded acoustic music. Cuts from Douglas, Barenberg, and Meyer's Skip, hop, and Wobble sounded outstanding on these speakers, with smooth, extended clarity, and excellent tight low-end on Meyer's upright bass. They sounded extremely"real" on this CD - like you were in the room with the instruments.

For classical recordings, the Sigma's are gorgeous. Not just in the sense of being stunning to listen to, but also because they're so detailed and real sounding.

During a vocal tracking session, I found the Sigma 6.2's to be nicely dynamic; and I easily heard ( and was therefore able to avoid) the negative audible effects of applying compression and limiting. I could also clearly hear the effects of subtly moving microphones around on sources, helping to avoid having to EQ tracks later when I mixed.

When used for mixing, the Sigma's extended top and bottom end ensure that you hear exactly what's going on in the extremes of the frequency spectrum, while the balanced neutral tone allows you to apply EQ and dynamics (where necessary) with complete confidence.

Earthworks has done an amazing job with the Sigma 6.2 monitors. The best compliment I can pay them is that, with well-recorded tracks and a good mix, the speakers seem to disappear; you just hear the music.

Special thanks to Hafler for the generous loan of the excellent TransNova 9505 amplifier used in this review.