Emerald Physics • CS2P Loudspeakers

by Guy Lemcoe | December 6, 2014


The CS in the model designation of this unconventional loudspeaker stands for Clayton Shaw, the designer of the original CS2 speaker introduced in 2007. In 2009, Walter Liederman purchased Emerald Physics from Shaw, and two and a half years later design and engineering responsibilities were given to Mark Shifter who, in addition to public-relations and export-sales duties, serves as lead design engineer. Working closely with Daniel Mullins in Canada on the in-house design of crossovers and drivers has resulted in major contributions to the brand's success in the market. Emerald Physics speakers are sold direct with a choice of two purchase options: with and without a home trial.

The new CS2P (the P stands for passive), unlike the original CS2, is designed as an upgradable speaker, so you can start with a single stereo amp and use the CS2Ps as conventional speakers utilizing the provided external passive crossovers. Later, you can add the new DSP2.4 digital processor/crossover ($850) to improve bass performance and tonal balance. Finally, you can disconnect the outboard passive crossovers altogether and add a second amp to take the final step toward optimal sound via active biamplification. This last configuration created a mystery that was finally solved after much head scratching and system dressing.

The CS2P is an open-baffle, three-driver, 2.5-way design with dual pulp-fiber cone 15" woofers and a 1" proprietary compression driver mounted on a 12"-diameter waveguide. The nominal impedance of the system is 4 ohms and it boasts 93dB sensitivity. Biamping increases sensitivity to 97dB. The published frequency response is 40Hz-20kHz +/-3dB. Using the optional DSP2.4 digital processor/crossover extends the bass response to 24Hz. The lower woofer rolls off at 200Hz, the upper one, being a woofer/midrange, crosses over to the tweeter at 1000Hz. Being dipolar below 1000Hz creates little or no lateral speaker output, effectively eliminating first reflections off side walls. Above 1000Hz, the speaker behaves as a direct-radiating monopole.

According to Emerald Physics, the following four design principles needed to be addressed for this open baffle speaker to be a success. First, in order to minimize room interactions and the resulting sonic signature, the company developed what they call BDC (Broadband Directivity Control) -- a method to control a loudspeaker's dispersion pattern and reduce or eliminate early reflections. Emerald Physics contends the speaker/room interaction has been one of the major problems in home audio systems. Eliminate this source of coloration and you get better sound. Their solution was to create a speaker with a controlled dispersion pattern and a more consistent pattern across the frequency spectrum. Put simply, with the CS2P, you listen mostly in the speaker’s direct field, thereby eliminating a large percentage of the room's sound. It’s like moving yourself significantly closer to conventional speakers and listening in the near field. This is said to lead to more accurate stereo reproduction and venue ambience.

Second, Emerald Physics has eliminated the "box" of most conventional speaker designs. The drivers are mounted directly onto a rigid 3 3/4"-thick baffle with no surrounding cabinetry. Thus, the baskets, magnets and wiring of the individual drivers are there for all to see -- a challenge to the wife-acceptance factor. In addition to saving the customer the expense of a large, heavily braced enclosure, this design is said to preserve the pitch and harmonic beauty of instruments, ensure flat bass response and eliminate impedance swings.

Third, a step toward the elimination of dynamic compression is achieved through the use of very efficient professional speaker components. With an efficiency of 93dB (97dB biamped), the CS2P reaches exceptional levels of dynamics and power handling. Such efficiency also enables the speakers to be used with low-power or inexpensive amps and still sound good.

Finally, due to the high efficiency and easy load presented to the amplifier, the CS2P is amp friendly and can reach very successful performance levels without the necessity of tubes further up the chain and exotic cables.

Even without a cabinet, the CS2Ps are heavy, weighing 85 pounds each. They stand 50 1/2" high, 22" wide and 16" deep (at the base). The woofer is manufactured in the US and the tweeter overseas, but both are easily available if replacement is necessary. They are firmly attached to the frame of the specially manufactured MDF baffle, locally sourced in Colorado where the speakers are assembled. The frame is rigid and solid. The review speakers had the optional automotive tri-coat black finish ($1200 extra), and they looked great. Protruding from the rear of the frame are the backs of the drivers. There is nothing esoteric or precious about these speakers. They are built solidly and without pretense. The crossovers, contained in nicely finished black metal boxes, fit neatly on the base of the speakers. I put them on back issues of Stereophile to provide some damping and protect the surfaces of the bases. Removing the jumpers enables biamping. I initially chose to run the speakers with one stereo amp, so I left the jumpers in place.

The CS2Ps were delivered in three boxes: one each for the speakers and one for the bases. Each speaker was sturdily packed in its box and the bases were likewise packed with care. Unpacking the speakers is a two-man operation -- these speakers are large, somewhat ungainly and heavy! The bases are attached to the bottom with six Allen-head screws. Determining that laying the speakers face down on a sofa with the base on the armrest would facilitate assembly, I recruited a friend to help wrestle the speakers into place.

Once the bases were attached and the speakers were upright, I waltzed them into position in the music room where my Acoustats once stood. My music room is on the small side, measuring 12’ 8"L x 12’ 4"W with an 8’ ceiling. The floor is carpeted and the room is well damped -- both side walls being lined with books, records and CDs. Fine adjustments in speaker placement were a cinch, because the speakers, being free of spikes, are user friendly and slid easily on the carpet. On bare floors, put a towel under the base and slide away. As time went on, I experimented with placement and found the initial location best. Measured from the center of the tweeter, the speakers stood four feet from the front wall, three feet from the side walls, eight feet apart and eight feet from my nose, toed in so I was looking directly into the center of the compression tweeters. Finally, to grille or not to grille? Not an issue, because the speakers are designed to be used without pesky driver covers.

After determining the best spot for the speakers, I sat on the sofa and just stared at them, mesmerized by their appearance. Conjuring up past hi-fi stereotypes, I thought to myself, These are what loudspeakers are supposed to look like. . . huge, stacked drivers staring back at you just itching for a signal. Being black and roughly pear-shaped, the CS2Ps reminded me of something I might observe through the fog skulking around Stonehenge late on a moonlit night.

My system has on occasion been referred to as "long in the tooth." Dated it may be, but I have always been entranced with the sound and have resisted making any changes. It has provided me a clear window on the performance replete with all the detail, image specificity and soundstaging I could hope for. I have resisted the perilous obsession with the upgrade path for a variety of reasons, foremost of which are: (1) I probably couldn’t afford it, and (2) I have not been overwhelmed by current high-end offerings. Sure, there is some great-sounding and fine-looking gear out there, but at what price? When cables have become akin to high-priced components and turntables, speakers and electronics cost three times what I paid for my car, I have just stood back, watching the prices spiral upward to absurd levels. How things have changed since I last wrote about high-end gear!

That said, my system consists of a Pro-Ject RPM 6.1 turntable with a Dynavector DV-20X cartridge firmly attached to the 'arm’s business end. CD/SACD playback is provided by a Sony DVP-NC685V. An Adcom GFT-555 tuner serves up FM broadcasts. Preamplification is via an Adcom GFP-555, and amplification is from an Adcom GFA-535 II. Loudspeakers are late-'80s Acoustat Spectra 22 full-range electrostatics. Their transparency, sense of scale and presence remain relatively unmatched in my experience. Interconnects, with the exception of phono, are entirely Better Cables Silver Serpent. The phono interconnect is a MAC Ultra Silver+ Sound Pipes (now Rite Audio Cable). Speaker cables are Synergistic Research Alpha.

During the course of this review I swapped out the Adcom amplifier for Emerald Physics’ EP100.2SE ($2200) and EP60.2 ($1000) for biamping. Additionally, I am indebted to David Salz and Will Horne at Wireworld who unhesitatingly supplied me with a set of Eclipse 7 interconnects and Mini Eclipse 7 speaker cables so I would be able to finish this review. The speaker cables in particular are unique in my experience in that you can change the jewel-like termination from spades to bananas or vice versa by just unscrewing the replaceable tip. Real or imagined, the Wireworld cables allowed the system to sing.

I have learned that most speakers require a break-in period, and the Emerald Physics CS2P is no exception. Mark Shifter recommended at least 150 hours before they would sound their best. I agree, because out of the box they sounded flat, uninvolving, with no sparkle in the highs and a noticeable lack of dynamics. Of course they sounded flat and unexciting! The tweeters were not connected! The crossovers had not been sent with the speakers. In my haste to begin listening, I had connected the amp leads to the lower sets of terminals, so I was only listening to the woofers and woofer/midrange drivers. Duh!

When the crossovers arrived a few days later, it was just a short time until I had everything wired up properly. The crossovers are hand built and internally wired point to point. They are housed in neat metal enclosures with clearly marked directions as to where the wires are to be connected. There are four terminals on the back of the box and four on the front. The front terminals for the amp leads were bridged for use with a single stereo amp. The rear terminals are connected via short strips of wire to the respective terminals on the back of the speaker. If using the speakers as a single-amped pair, make sure the red wires (tweeter) are connected to the upper binding posts on the speaker. The white wires (woofer) go to the lower speaker terminals.

My one concern regarding all of this was the lack of an owner's manual. I wished an illustrated manual was included with the review speakers, discussing in detail the design, assembly, placement and connection options. Fortunately for future owners, Emerald Physics now includes this documentation. Finally, because there are so many dust-gathering surfaces on the CS2Ps, if I owned them I’d make "socks" out of soft, dust-resistant fabric to cover them when not in use.

My first impression after connecting the Emerald Physics speakers to my Adcom amp was that I was listening to my Acoustats suddenly blessed with increased dynamics, as if my speakers had suddenly grown a pair of cojones. Compared to the relatively inefficient Acoustats, the 93dB-efficient CS2Ps necessitated a downward turn of the volume control to keep the music at a comfortable listening level. To overcome this difference, I inserted a pair of Harrison Laboratories 12dB/octave attenuators and plugged the leads into those. Problem solved with no adverse effect that I could detect.

Along with an increase in the dynamic "jump factor," the sound of the two speakers was strikingly similar. Like the Acoustats, the CS2Ps gave a crystal-clear view of the musical performance set on an impressive soundstage. Refreshingly absent, however, was the feeling I have had with my Acoustats that I was listening to a pair of giant headphones, my head in a vise between the speakers. Instead, with the CS2Ps, I was treated to a sense of space seemingly unhindered by the physical presence of the speakers. Indeed, the CS2Ps simply faded into the background. I could get up and move around without losing the soundstage's perspective. This new sense of freedom was welcomed.

I look forward to Saturday mornings when I listen to one of my favorite radio programs, Hearts of Space, on the main system. In syndication since 1983, Hearts originates from San Rafael, California, featuring music of a reflective nature from the ambient, new age, Celtic, world and electronic genres where, in the course of an hour, you can hear music as dissimilar as Native American flute, Charles Ives and Tangerine Dream. I enjoy sitting and listening to the wide variety of music Stephen Hill plays, especially after I installed the Emerald Physics CS2Ps in the system. Their ability to throw a wide, deep soundstage with pinpoint imaging allowed me to lean back and drift off into the music’s varied soundscapes. Also, I was treated to some of the most detailed, balanced, full-range sound I have heard in my listening room to date. If the Emerald Physics speakers sounded this good without any signal processing, I wondered what they would sound like with the DSP2.4 connected.

Thus stoked, it didn’t take long for me to connect the DSP2.4 configured for single-amp performance. It contains a 24-bit/48kHz ADC, a 24-bit/48kHz DAC and a programmable processing chip. The DSP2.4 is designed to be inserted between the preamp and amp, where it digitizes the analog signals and ostensibly flattens out the frequency response of the loudspeakers and extends bass response to 24Hz. In addition, image focus is claimed to be improved due to elimination of front- and side-wall reflections. My ears told me Emerald Physics was successful on all counts. After installing the DSP2.4 and either the 100Wpc or 60Wpc amp provided by Emerald Physics, the first thing I noticed was a noticeable decrease in volume on all inputs with the volume control on my preamp set to its normal 9:00 position. Turning the volume to 12:00 brought the desired loudness. After several hours of listening, the speakers, which had been relatively unobtrusive but noticeable before the DSP2.4, completely disappeared after the installation. All aspects of the sound improved, with an increase in bass being most noticeable. Not only was it extended, it was tight as a drumhead with fine pitch definition. The two amps sounded identical, except for more oomph from the more powerful amp. For example, I listened to the Audio Fidelity LP of Vangelis’s music for Blade Runner [Audio Fidelity AFZLP 154] and heard for the first time the subterranean bass (24Hz or thereabouts) mastering engineer Kevin Gray determined was present using his spectrum analyzer.

The CD soundtrack to Dances With Wolves [Epic ZK 46982] presents the music on a huge soundstage with enormous depth. The room-massaging bass drum and distant trumpet in "The Main Title -- Looks Like A Suicide" suggested great things to come. And they did come! From the mournfully hollow, lilting timbre of Djivan Gasparyan’s duduk on the I Will Not Be Sad In This World LP [Opal 1-25885] to the precise, percussive sound of Glenn Gould‘s favorite Steinway (known as CD 174) on the Goldberg Variations (LP [Columbia ML 5060]), the music sounded right to these ears. As my listening continued, I began to realize the synergy created between the speakers, amps and cables, nothing artificial added to the music in any way.

The music had such presence and dynamics I felt I was in the recording studio with Sarah Vaughn and the all-star band accompanying her on the SACD of her self-titled Mercury recording [Verve B0001127-06 IN02]. I had no idea this monaural set from 1954 could sound so good! The quirky, timbre-rich Canadian group the Henrys ([Puerto Angel CD [Bar None Records AHAON-079-2]) was heard to great effect on the CS2Ps. The Dobro, acoustic and lap steel guitars, acoustic bass and percussion on "Coyote Basin" sounded perfect on a recording that's as natural as could be. I have never felt as close to Dylan’s music on the SACD of his 1974 masterpiece Blood on the Tracks [Columbia CH 90323] as I did through the CS2Ps. Not only could I understand every word of the lyrics for the first time, but I sensed the urgency and pace of the performance.

No doubt the Emerald Physics amplifiers -- stereo class-D digital units with custom analog power supplies designed by contract engineer John Levreault -- contributed to the fine sound I was hearing. They are stable to 3 ohms and bridgeable, increasing the wattage from 100Wpc to 275Wpc for the EP100.2SE and from 60Wpc to 150Wpc for the EP60.2. The "SE" designation refers to units with upgraded caps, resistors and inductors, as well as a larger power supply that helps the amp deliver 20% greater current. Available in nicely milled aluminum cases in silver or black finish, they have a relatively small footprint about 10" square and standing 3.5" (EP100.2SE) or 2.5" high (EP60.2) on spiked feet. Each has RCA and XLR inputs and solid gold-plated copper three-way binding posts. On the back are two pushbuttons: one for bridged operation and the other for lifting the ground. The only adornments on the front are an on/off rocker switch and small green power LED. As to their sound, I couldn’t find anything to criticize and did not feel deprived of any musical information. They seemed well matched to the Emerald Physics speakers.

After many weeks of enjoyable listening at a sonic level rarely achieved in my room, I was confident I had a handle on the sound of the CS2Ps and, being content with the performance of the single-amped CS2Ps, felt this review was a wrap. I had forgotten an important point, however. Mark Shifter had insisted that I give a listen to the speakers in a biamp configuration, promising I would be amazed at the sound. I was somewhat skeptical, but since I had agreed to this additional system configuration at the outset, I was finally ready to reconfigure the system for biamping using the specially programmed DSP2.4 and additional cabling.

The first step in this process was to disconnect the external crossovers entirely from the backs of the speakers. Then, the single–amp configuration was replaced with the biamp, and the additional cables were brought out of their boxes. Both the EP100.2SE and EP60.2 were placed into service for this task. I figured I’d use the 100Wpc amp for the bass drivers and the 60Wpc amp for the midrange and treble, so I planted my butt on the floor and proceeded to make the connections.

After spending the greater part of an hour and with the selector switch on the preamp set to FM, I hit the power switches in anticipation of great sound. It was not to be! Instead of music coming from the speakers my ears were assaulted with howls of electronic feedback and screeches of tweeter-destroying noise. What the. . . ? It turned out the problem was with high EMI emissions, to which class-D amplifiers are prone, coming from one of the amps and interfering with my FM tuner. Turning off the tuner solved the problem. Later, I determined the problem was with the EP60.2. When I replaced it with my trusty Adcom, the issue went away.

"More meat on the bones" was my first reaction to the biamped system. Wow, these speakers project. On certain recordings it sounded like I was in the room with the speakers when, in fact, I was in another. Across-the-board improvements in dynamics and soundstaging did not begin to tell the whole story. What was only suggested in single-amp mode was brought forth in three-dimensional splendor with a "reach out and touch you" quality with the biamp setup. Ambient cues were brought into clearer focus than ever. Sunset Sound’s studio was especially illuminated on Jackson Browne’s The Pretender CD [Asylum 6E 107-2]. So was Columbia’s 30th Street Studio on Miles Davis’s Someday My Prince Will Come LP [Columbia/Music On Vinyl MOVLP 494]. The leader’s closely miked Harmon-muted trumpet pierced the air in the room with perfect "bite." In fact, this album sounded so good now, I’m tempted to amend my original review of the sound of this record by adding another full star.

As expected, bass extension was noticeably improved, with tautness and impact that enabled the bass-drum whacks in track 1 of Dances With Wolves CD to roll across the carpet. The "What the hell kind of drum is that?" on track 5 of the same CD had a tonality and resonance totally different from that on the opening track and startled me with its power. One minute into track 8, John Barry must have found an even bigger bass drum than the one on track 1. It was deeper and rounder -- and also the first time I heard it from my system. Similarly, the truly subterranean bass in the opening "Main Titles" of the soundtrack to Blade Runner pressurized my room. The ominous opening to the Black Hawk Down soundtrack [Decca 4400170122], featuring a wide variety of electronic, acoustic stringed and percussive instruments, filled the room with palpable sound. I was hearing more low-frequency content on every recording I played.

This was revelatory. Listening to music without hearing the full spectrum of sound from low to high is like sipping a margarita without adding tequila anejo. Playing back with peak SPLs of 87-90dB, the effect was not only exciting but downright intimidating. These speakers like to be played loud, yet I never felt the speakers were on the verge of collapse. They just kept on making music, with no hint of distortion, overload, loss of texture or delicacy, as the volume knob was turned clockwise. They sounded fine at lower volume levels too. Denez Prigent’s plaintive and Lisa Gerrard’s angelic voice on the Breton song of longing and despair, "Gortoz A Ran -- J’Attends," from Blackhawk Down nailed me to my chair. The sensation of actually being in a cave on the opening cut of Andreas Vollenweider’s Caverna Magica LP [CBS FM 37827] was quite convincing. I had selected this recording for the first few seconds of that track, but I ended up playing the entire album, so captivating were the music and sound.

To sum up, I found there was nothing not to like about these speakers, no matter how they were used, although they certainly make put their best sonic foot forward with the DSP2.4 and a pair of amps. They fulfilled my wishes for reproduced sound (extension at the frequency extremes, lustrous midrange, tactile soundstaging, speed, solidity, and dynamic prowess) and for speakers in general (easy driveability, affordability and maneuverability). I found the speakers to be quite neutral and revealing of the program material; they will not make a silk purse out of a sow’s ear, and if a recording was on the soft or hard side, the sound reflected that fact. If a recording was compressed, it sounded so. When fed the right signal, the speakers created excitement by offering a dynamic, transparent, full-range re-creation of the musical event, however large or small.

Unlike some speakers that seem best suited for certain types of music, the Emerald Physics CS2Ps were comfortable with everything I threw at them. From acoustic to electronic, symphonic to jazz, the CS2Ps simply reproduced the music without editorializing. So revealing are these speakers that they would make excellent tools for equipment and music reviewers. No doubt they would really sparkle in a larger room, but I could not fault them in my smallish one. So enthralled was I with the sound of these speakers that I didn’t want to shut the system down. It seemed that every record or CD I played revealed new information in a new way.

As fine as the Emerald Physics CS2Ps sounded, however, whether single- or biamped, I did not feel compelled to retire my Acoustats. Like a well-worn pair of favorite shoes, they seemed like an old friend: comfortable, true-fitting and right. But if I ever needed to replace my speakers, I would be quite satisfied with the Emerald Physics CS2Ps, knowing I would not be giving up anything in terms musicality and emotional involvement and gaining a few important things in the process.

Prices: CS2P, $2490 per pair or $2990 with 30-day trial; DSP2.4, $850 or $490 when purchased with speakers.
Warranty: Five years parts and labor.

Emerald Physics
2150 West 6th Ave., Unit I
Broomfield, CO 80020
(720) 726-4548

Associated Equipment

Analog: Pro-Ject RPM 6.1 turntable, Dynavector DV-20X cartridge, MAC Ultra Silver+ Sound Pipes phono cable.

Digital: Sony DVP-NC685V CD/SACD player.

Tuner: Adcom GFT-555.

Preamplifier: Adcom GFP-555.

Digital Signal Processor: Emerald Physics DSP2.4.

Power amplifiers: Adcom GFA-535 II, Emerald Physics EP100.2SE and EP60.2.

Loudspeakers: Acoustat Spectra 22.

Interconnects: Better Cables Silver Serpent, Wireworld Eclipse 7.

Speaker cables: Synergistic Research Alpha, Wireworld Mini Eclipse 7.