June 2005

The Nearfield
Tale Of Two Monitors
Article By Steven Stone

  This month we'll look at two different but equally impressive speaker systems from well-known and respected manufacturers. Each espouses a different approach to solving the same sonic problem — how to create a loudspeaker with a small footprint that can deliver nearly full-range musical content. Which is "better" depends on your own musical and sonic preferences. Both can deliver music in a nearfield environment with a level of veracity that can rock your world.

Aerial Acoustics Model 5B
Since his first design, the model 10T, Michael Kelly has been known for his conservative, but beautifully engineered designs. Instead of featuring radical technology or unusual components Kelly concentrates on refining the aspects of a speaker's design that he feels contributes most to his goal of creating a neutral and revealing loudspeaker.

The Model 5B epitomizes the Aerial Acoustics design philosophy of building a product that serves the music as perfectly as possible. It resembles not so much a high fidelity component as a finely made piece of furniture. My review sample was done in Aerial's Rosewood veneer finish. You had to look closely at the edges of the rounded corners to see the cabinet's seams. Great attention was paid not only to book-matching the front panels, but also to the top and sides of the cabinets. Compared to the Reference 3A Dulcet I reviewed last month the Aerial displays an extra level of finishing finesse.

Technically the 5B eschews flash for solid design. Its small 13" x 7.9" x 10.3" (HxWxD) sealed enclosure houses two drivers, a 1" Titanium dome tweeter with a vented pole, and a 7.1" long stroke Bilaminate cone midrange/woofer with a 1.5" coil. The dome tweeter sits behind a honeycombed metal shield to protect it from finger pokes and kitty cat claws. The 5B comes with removable speaker grills, but once you've seen the speakers sans grills, I seriously doubt you will reattach them. Two pair of large five-way binding posts on the back of the speaker permit either regular or bi-wire connections. The back of the speaker also sports a built-in connector for attaching the speaker to a proprietary heavy-duty wall hanger. At 22 lbs, this speaker feels as substantial as it looks. 

The 5B's 85dB efficiency and nominal 4 ohms (3 ohms minimum) impedance could be a problem for some low-power tube amplifiers. Single-ended aficionados may find their favorite amplifier not quite up to the task. But judging by the power level meters on my Accuphase P-300, any tube amplifier capable of putting out at least 40 watts, or any 100 watt solid-state amp should have no trouble driving the 5Bs to satisfying volume levels.

The 5B comes in three different finish versions. In smooth black the 5B lists for $2000 a pair, in natural cherry, rosewood, or bird's eye maple it costs $2200, and in gloss black, gloss silver, or two-tone gloss black and silver it will set you back $2400. For desktop use I'd recommend the basic black or one of the wood finishes. Gloss black or silver strikes me as slightly over-the-top. It could get tedious constantly removing smudged fingerprints and fondle-marks.

Hardcore CRT monitor users may be distressed to find the 5B is not magnetically shielded. On my desktop I discovered that if I placed a 5B closer than 6 inches to the sides of my 19" monitor it could introduce color deformations. Sometimes even passing a speaker too near the monitor during set-up would impose some color shifts that required demagnetization. However, once set up at a prudent distance from my CRT I experienced no further color monitor problems.

I tried a number of different placements before I finalized their location on my desktop. Unlike the Reference 3A Dulcet, which ended up firing straight ahead, parallel with the front of my desk, I ended up toeing in the 5Bs at an angle so that from my main listening position I couldn't see either sides of the speaker cabinet. I also put an extra inch of rise on the front of the cabinets so the speakers pointed slightly upwards. This created the widest soundstage coupled with the most precise imaging. The only negative resulting from this set-up was a somewhat smaller listening window than if they were set up parallel with the front of the desktop.

The Sound Of An Aerial
Although they weren't designed as desktop speakers (the lack of magnetic shielding gives this away), the 5B's are nearly perfect for such an application. Their sealed box design delivers a gentle bass roll-off that can easily be blended into a subwoofer. You could use them sans subwoofer if you don't mind losing a bottom octave. I found the 5B's could put substantial bass levels down to 50Hz, at which point they rolled off gracefully. Their long-throw midrange woofers could also handle substantial amounts of low frequency power. Even when subjected to 15Hz test tones the drivers didn't move in an unhealthy manner. Compared to the Reference 3A Dulcets the Aerial Acoustics 5B's bass response displayed superior definition and inner detail. Danny Thompson's acoustic bass on Darrell Scott Live in NC had much better dynamic acuity and weight through the 5B's.

Upper frequency response ranks as one of the 5B's strong suits. The Titanium done tweeter combines refreshingly smooth response with exemplary extension. Compared to the Reference 3A Dulcet I noticed more air on flutes and violins. Unlike some speakers that deliver more treble information, the 5Bs retain a very musical personality even on less than stellar recordings.

As you might expect from small two-way speakers, the 5B's image beautifully. On my own live concert recordings the soundstage displayed impressive and realistic depth, width, and three-dimensionality. On well-recorded commercial recordings such as Old School Freight Train's Run (Acoustic Disc ACD-61) the 5B's articulated the finer details of each instrument's physical placement with grace. The 5B's also demonstrate excellent low-level definition and retention of inner details. You can hear deep into a mix even at moderate levels with little need to turn the volume above a comfortable setting.

With both of my reference amplifiers, the Bel Canto EVO-2 and Accuphase P-300, the 5B speakers evinced a seductive level of musicality coupled with remarkable harmonic neutrality. Regardless of the source, the results were always listenable. Even after long-term listening sessions with less than perfect sources at boisterous volume levels, I never suffered from bouts of listening fatigue.

The Aerial 5B's handled dynamic contrasts quite well for a small two-way speaker. While not quite as impressive in this regard as the three-way Thiel PCS speakers, I never got any sense of dynamic compression during low-volume passages. Only when playing loudly did I notice a bit dynamic restriction limiting the dynamic contrast between forte and triple forte passages.

If you devote long periods of time to critically listening at your desktop the Aerial 5B may be ideal. It combines superb definition with musicality and neutral harmonic balance. Even after extended listening sessions you will find the Aerials as refreshing and involving during the last half hour as they were during the first ten minutes. In short, the Aerial 5B easily rates the approbation as a superb desktop monitor.

Thiel PCS Speaker
Jim Thiel has a well-earned reputation for making highly detailed and dynamically accurate loudspeakers. His smallest offering, the PCS, was first introduced in 2000. If you long for a desktop monitor that can maintain its sonic integrity even while delivering rock and roll recording at studio playback levels, the PCS may well be your perfect desktop loudspeaker.

PCS stands for personal coherent source. Like most Thiel speakers the design goal for the PCS was to create a speaker with tonal, spatial, transient, and dynamic fidelity. To accomplish these goals in a small footprint enclosure, Thiel developed a special coaxial midrange tweeter. This driver incorporates a 4" anodized aluminum midrange diaphragm with a 1" anodized aluminum dome tweeter. This compound driver uses a mechanical crossover that couples the two speaker diaphragms at lower frequencies so the cones move in unison, but at higher frequencies the suspension decouples the mass of the midrange driver from the tweeter. This physical crossover combines the power handling capabilities of two separate drivers with the phase coherence of a single unit. Optimizing the compliance and damping of the compound driver makes it possible to achieve uniform frequency response from 100Hz up to 20kHz.

Ever since the beginning Thiel's crossovers have employed 1st order crossover systems to minimize phase distortion. With only 6dB of roll-off per octave this kind of crossover demands drivers with a wide bandwidth and smooth natural roll-off characteristics. Since Thiel builds his own proprietary drivers they can optimize performance characteristics to insure optimum response with this kind of crossover.

The PCS 6.5" woofer has an aluminum diaphragm that combines rigidity with ultra-light weight. Its lowest internal resonance occurs at 4.5kHz, over 2.5 octaves above the crossover frequency. Like all Thiel woofers this driver has an underhung (short coil/long gap) motor system that allows linear travel up to 3/16 of an inch. This design insures that the voice coil is always within the magnetic gap, which prevents the magnetic strength on the coil from varying even during maximum excursions. Thiel uses a copper pole sleeve to reduce the speaker coil's inductance and stabilize its magnetic field. With a 2.5 lb. magnet, 6 lb. total magnet structure, plus a 1.2 lb. shielding magnet, the PCS woofer displays a level of technological finesse not found in many small speakers.

The PCS cabinet incorporates all the physical refinements of Thiel's larger speakers, including a low-diffraction curved front baffle, two inch thick front baffle, 1 inch thick cabinet walls, extensive internal bracing, and a sloped front that correctly time-aligns the coaxial driver with the woofer. Thiel offers a mind-boggling range of cabinet finishes including walnut, white oak, birds-eye maple, natural cherry, back ash, teak, amberwood, striped mahogany, dark cherry, morado, or silver. Grille fabric colors include white, cream, beige, brown, grey and the ubiquitous black. The grill attaches via five small magnets rather than with metal clips or pressure-fit plastic. My review sample sported the conservative but elegant combination of dark cherry veneer with a black grill.

A single pair of five-way binding posts on the back of the speaker and countersunk screw posts for attaching spikes on the bottom of the speaker completes the PCS's topology. As you might expect from a $3000 a pair speakers, the PCS's fit and finish looks perfect, even to a critical eye used to examining $150,000 mandolins.

Thiel PCS On A Desktop
Combining a three-way design with a ported cabinet results in a small footprint speaker that can combine well above average bass extension with exemplary dynamic capabilities. But to delver optimum performance you must pay careful attention to the PCS's set-up. Because of its above average bass extension and low frequency energy you can have too much of a good thing if you aren't careful. I found that raising the speakers up on a combination of ceramic cones and absorptive pads, toeing them in so I couldn't see either side wall, and lastly, placing a small foam plug in the port, gave me the most even bass response on my desktop.

According to Jim Thiel, "The PCS was balanced for stand placement. When placed on a desk the difference in bass balance isn't too much if the listener is in the far field. But if you are sitting nearfield with the speakers on a desk there will definitely be a boost to the lower frequencies that is not accurate. Some people like it, but if you don't, then blocking the port will improve the level of the bass on average. It's not a perfect solution — the upper bass/ lower mid might still be somewhat strong, and the lowest bass provided will be a little weak — but on average an improvement."

I found the size and density of the foam plug made a noticeable difference in the amount of bass attenuation. For my set-up a 2.5" by 1" piece of open cell foam in the port delivered the best overall frequency response. Sometimes, depending on the source material, I removed the plug. It worked as sort of a physical bass contour control.

Thiel PCS Performance
Listening to the Thiel PCS speakers reminds me of my first experience with a high-performance automobile. Back in 1981, a friend of mine purchased a Ferrari California that he let me drive it on a highway leading out of Boston. At first I was not impressed. The car seemed stiff and not terribly responsive, but as the speedometer edged above 90 MPH something magical happened. Its truck-like handling changed as it hunkered down, and transformed into the most suave ride I'd ever experienced. At 120 MPH the Ferrari became even more sure-footed, like it was on rails. Wow, what a party!

The Thiel PCS speakers, like that Ferrari, need to be pushed if you really want to see what they can do. At moderate volume levels they sound very good, but at higher levels they deliver a level of dynamic agility that eludes all but a few great speakers. The last time I heard a pair of studio monitors that could handle high volume levels with such equanimity was at a recording session with the String Cheese Incident. Producer Malcolm Burns was using a pair of Meyer UPA-1P active monitor speakers. These transducers were originally made for on-stage use and their primary virtue is that they can play exceedingly loud without distress. With the right amplifier the Thiel PCS can easily match the Meyer UPA-1P's high-level performance.

Even though the Thiel PCS speakers are rated at 87dB/W/m efficiency at one watt, if you want to make them shine you'll need an amplifier with some backbone. The Accuphase P-300 and Bel Canto EVO-2 amplifiers both mated with the PCS speakers quite well while the Sound SE 100 single-ended triode amplifier did not.

What else can Thiel PCS speakers do besides play loudly? A better question might be what can't they do. In every performance parameter that matters the Thiels deliver impeccable sonics. They image precisely, have superb low-level detail, and remarkably neutral harmonic balance through their lower midrange. Compared to the Aerial Acoustics 5Bs the Thiel PCS speakers have a slightly more forward soundstage and a whisper more upper frequency extension. The PCS speakers also deliver more lower midrange and upper bass energy, which depending on your tastes, may or may not be to your liking. In terms of overall harmonic balance the Aerials seem a trifle more relaxed and musical, while the PCS have a matter-of-fact presentation through their midrange coupled with more robust lower frequencies. Both speakers deliver equal levels of three-dimensionality and lateral focus, but the Aerial 5B's have a slightly smaller listening window.

When you consider the Aerial 5B's are only 2/3^rds the price of the Thiel PCS speakers they appear to be a better value. But if you regularly exceed 92dB listening levels the Thiels quickly become the lead horse in this race. Think BMW M5 compared to a nice BMW 321.

The only downside of the PCS speakers, besides their possibly overabundant bass, stems from their virtue of being able to play loudly with so little apparent strain. Most likely you will play music louder because you can, and since the PCS speakers do this so effortlessly you may discover that you are listening to music too loudly for too long. At best you may induce some listening fatigue, at worst tinnitus. Just like with any high performance device, you must be careful not to get too carried away. But if you operate them in a sane adult manner the Thiel PCS speakers will reward you with an exciting ride. Vroom, Vroom.