Feb 1, 1998 6:05 PM, By Don Gehman

DUAL-CONCENTRIC POWERED STUDIO MONITORS

Tannoy has been manufacturing loudspeakers since the late 1920s and has found great success with its trademark dual-concentric driver designs in the studio marketplace worldwide. The term dual concentric is defined by Tannoy as a coincident point source speaker, in which the woofer cone acts as a seamless direct extension of the high-frequency horn, yielding a constant directivity pattern with linear amplitude and phase response in both horizontal and vertical axes.

Priced at $3,995 pair, the AMS 8A is the latest product offering from Tannoy and part of the family known as AMS (Active Monitor Series comprising the 10A, 12A and 210A active sub in addition to the 8A being reviewed). The cornerstone of this AMS 8A is an 8-inch dual-concentric low-frequency driver concentrically mounted to a 1-inch HF compression driver with a damped tulip-shaped waveguide. The drive unit is housed in a charcoal-black, slat-side inlay, inert DMT (Differential Material Technology),front-ported cabinet. The twin laminated, space-frame design of the cabinet is heavily braced and decoupled to prevent signal coloration. All contoured cabinet edges feature isolation pads for added durability. The quoted frequency response is 38 to 25k Hz, ±2.5 dB.

The bi-amped MOSFET power modules deliver 140 watts continuous to each of the HF and LF sections. The amp’s construction techniques and components are reminiscent of high-end audiophile amps I have worked with. Heat is dissipated via the massive double-anodized, aluminum-finned back plate. A blue LED on each cabinet’s front panel indicates power on.

The layout on the back of the amplifier plate is well marked and easily followed, and the switches allow for easy adjustment access. Beneath the fuse holder is a subassembly that conveniently holds spare fuses. Operating voltage is switchable between 100 and120V and 200 to 240V.

The active circuitry in the crossovers utilizes high-grade, 1% precision-matched components yielding tolerances within 0.25 dB throughout each passband. The sophisticated active crossover shaping and design (a Tannoy secret) produces not only a tight amplitude response, but also linear phase response. Tannoy is confident in its accomplishments: The literature bluntly states that the AMS Series monitors are the most phase-coherent, dynamic reference monitors in the world—period. Each AMS System is then tested, graphed and must acoustically fall within a 0.25dB window before being given the okay for shipping.

The AMS range of studio monitors do not use compression or limiting circuitry. Asked about this, a Tannoy representative simply stated that music by its very essence is dynamic, and squashing dynamics to protect a system may allow the system to play louder, but it’s not musical. The only form of protection is noted as a Poly Temperature Coefficient (PTC) device that prevents what Tannoy defines as catastrophic bass driver failure: shutting down the LF only when the system is being driven to a point where physical failure of the drive unit is imminent.

There are two filter controls: LF alignment allows a quick change-over between fourth- and sixth-order filters. The fourth-order is the natural -24dB-per-octave slope of the low frequency in a vented enclosure. The sixth-order tuning allows for gentle LF equalization to extend the -3dB downpoint to just above the system’s vent resonance, where it actively rolls the bass out with a steep 36dB-per-octave slope. Tannoy suggests fourth-order for critical monitoring and the more aggressive sixth-order filters for playback.

The second filter set is HF boost (air), which raises the level of HF energy above 17 kHz to increase the openness of certain material. This feature is described as an effect filter and should be employed based on the user’s subjective criteria. A Neutrik Combo connector accepts XLR or 1/4-inch TRS inputs, with gain trim to match -10dBm or +4dBm levels.

In Session
As a producer, the studio monitors that I use are synonymous with a painter’s blank canvas or a sculptor’s hammer and chisel. They are tools for creativity and, as with any tool, they take a little getting used to.

When I unpacked the AMS 8As, it took me a fair bit of time to position them properly. Subtle changes in positioning were quite apparent, due to the time alignment being superior to anything I had used previously. The blue LEDs are brightest when you’re looking into the sweet spot of the monitors, which was helpful as a guide, but not always absolute in different room environments. Once positioned properly, the AMS 8As exhibit astonishing clarity and detail not only on-axis but off-axis. This characteristic allowed me to move around my console and outboard gear without experiencing dramatic changes in frequency response.

For me, mixing has always been a battle of making a mix sound good on five different studio monitors. If it sounds good on five monitors, the mix will sound good on all speakers. But with further evaluation of that thought process, none of them would really be right, and all of them would have extensive coloration that I might have overcompensated for. You always walk out of a mix feeling like you missed.

Using the Tannoys to play back mixes I’d previously done, my immediate reaction was that some aspects could have been improved, such as tonal balance, imaging or things as subtle as choosing a different compressor or effect for certain passages. This results from the fact that the Tannoys do not exhibit the level of group delay or phase distortion found in traditional two-way designs. The monitors’ lack of coloration allowed my ears to immediately know what was going on where and from which aspect of the mix.

The AMS 8As can be really discouraging to listen to because they are so brutally honest. When I played back my work on Tracy Chapman’s New Beginning, I immediately noted the bass was a little tubbier than I would have liked and the top wasn’t quite as silky as I would have hoped for. And Hootie’s Fairweather Johnson was a little bright in the top end, but the bottom was really clear and the midrange was right on. Comparing these results to what I heard on many other systems so many times, I knew the AMS 8As were providing the truth.

My mixing style suits the sixth-order LF alignment over the fourth-order tuning. This is contrary to Tannoy factory recommendations, but having the choice allows me to use what works best for my particular style. I prefer the added extension provided by the sixth-order setting to the more gradual roll-off of the fourth-order setting. Mixing on the AMS 8A, I realized that if I could get the mix sounding great on these monitors, the mix would translate to any speaker a consumer could have and still sound great. This results in saving time, effort and—the bottom line—money.

Another advantage of active powered systems is consistency: The monitor, the amps and crossovers are constant, no matter where you use them. The more facilities I used the AMS 8As in, the more I learned about the acoustical deficiencies in the various rooms, allowing a firm reference point for accurate set up and consistent results.

The End Result
When my work went to mastering from AMS 8A mixes, there was virtually nothing to adjust. Consequently, when they come back from mastering, I’m able to hear what should have or should not have been done and send it back so they get it right. The end result is better-sounding product for the artists and their fans.

The Tannoy AMS 8As are truly superior monitors. As I mentioned earlier, these are tools. As a mixing tool, they are difficult to get accustomed to, because your preconceived ideas about monitoring are being challenged by a solution that is truly “tool”-oriented. They require discipline, perseverance and a belief that they really are the truth.

For the serious working engineer/producer, truthful reproduction is a good thing as it demands that you improve your technique and become a better engineer. Frankly, I’m not interested in “warm and fuzzy.” I’m interested in improving as a professional. Studio monitors are a lot like human beings: You must live and work alongside them for some time before you can draw a fair portrait of their qualities and imperfections. These monitors will not be returning to the factory.

Tannoy, www.tannoy.com.

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Lab Analysis: Tannoy AMS 8A
by Mike Klasco

Physical Characteristics
The wood-stock (MDF) cabinet construction is unusually hefty, with a 11/8-inch thick (!) front baffle with two flared “anti-chuffing” bass reflex ports; the other enclosure sides are 5/8-inch MDF, with a brace behind the driver. The large (3/4-inch) radius edges use L-channel wood strips with rubber antiskid inserts. One-inch-thick open cell foam lines the enclosure.

The woofer’s curvilinear polypropylene cone and rubber surround materials are more stable (less sensitive to humidity) and higher-performance materials than a paper cone/foam surround. The cast frame—thin (but strong), providing fewer acoustical reflections—is less resonant than a stamped steel frame and does not drain flux from the magnet structure. Its flat spider tends to be more linear than cupped spiders. The chamber behind the spider and magnetic structure is well vented to lower air modulation noise and reduce power compression (voice-coil heating) effects.

Coaxially mounted behind the woofer, the aluminum-dome HF compression driver uses the woofer cone as the horn, a technique pioneered by Tannoy decades ago. The phase plug is a unique low-distortion/low-compression ratio design. Clay material on the back plate damps driver motion against the enclosure brace; the speaker is not magnetically shielded.

The amplifier/active crossover in this bi-amped system has no sub-enclosure, so components are exposed inside the cabinet. The heat sink fins resonate audibly when the enclosure is thumped; this might be audible in a quiet auditioning room under some listening conditions. The Class-A/B amps have an op amp front end and MOSFET outputs. Power supply is analog with a torroidal (low hum field) transformer.

Acoustical Characteristics
The sound coverage pattern is tight and should have few reflections off nearby surfaces (such as the console), resulting in a more consistent sound from one monitoring environment to the next. The system’s impulse response was excellent, with a coherent pulse characteristic and fast settling time. (This is what coaxial speakers are supposed to be about.) Response extends past 15 kHz with a notch in the response (which appears only on-axis) centered around 18 kHz. Distortion, measured at 90 dB (@ 1 meter) and from 100 Hz upward, was well below 1%, and significantly lower over most of the compression driver’s operating range. Spectral contamination (clarity) was very good, with speaker self-noise about -50 dB down from the input signal.