MOORE'S LAW

Ribbon Loudspeakers by Newform Research.

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What does ADA mean for High Fidelity audio?

Some audio hobbyists will argue that ADA robs them of the chance to mix and match their favorite speakers and amplifiers. Also, some will undoubtedly prefer to use tube electronics. Perhaps the industry can accommodate these segments while still bringing the unprecedented benefits of ADA to High Fidelity's mainstream. The benefits of ADA in high fidelity include cheaper front-end electronics, higher fidelity input to speakers, and much more speaker design flexibility.

1. A penny saved....

No more sinking money into huge transformers, massive heat sinks, expensive crossover components, multiple chassis & power supplies, or exotic cables. In many high-end loudspeakers the inductors in the bass crossover alone can cost more than the digital audio chips we're talking about here.

ADA will replace many components of a traditional audio system and allow systems designers to shift budget to speaker drivers. Most designers will agree that using high quality drivers is money well spent. While ADA will be priced like any commodity computer chipset, good speaker drivers will remain high price items. Advanced magnetics, high precision mechanical assembly, limited markets, and hand fabrication will conspire to keep quality driver prices relatively dear.

Even if ADA only equaled the quality of our current rat's nest of preamps, amps, DAC's, cables, and crossovers, the increased expenditure on drivers alone would improve fidelity at any given system price point. This is only the tip of the iceberg.

2. Garbage In, Garbage Out

There's a school of thought that says that a speaker can only sound as good as the electronics feeding it. Replacing the speaker correction DSP, DAC, preamp, amplifer(s), and analog crossovers with a tightly integrated digital solution will provide higher signal fidelity at lower cost. With ADA there is no preamp, no analog parts variance errors, no analog parts drift, no compression in analog crossovers, less loop area for RFI problems, etc. Digital amplifiers are receiving good reviews, and they will only get better as the market focuses its resources.

Some high enders are so concerned with signal fidelity that they use outboard power supplies like the $1000 PS Audio Power Plant 300. These devices resynthesize an AC waveform from household AC to get a more constant and noise free voltage for sensitive electronics. Some digital amplifiers, like Cirrus's, monitor power supply voltage and take it into account when calculating the output. Yet another $1000 to be spent elsewhere in an ADA system since a $15 chipset will remove the need for the component.

3. Synergy is the speaker designer's friend.

Digital audio pioneer Meridian has been producing highly acclaimed active loudspeakers for years. Meridian's designs exploit the advantages of integrating DSP, DAC's, and (analog) power amps into the speakers. There are no exotic drivers or revolutionary amplifiers and yet their systems are some of the highest rated in the industry.

By performing all signal processing in the digital domain and designing each stage to work in tandem with the next, Meridian is able to extract a high level of performance from the components used. The same chips, amplifiers, and drivers used in more traditional stand-alone equipment would result in a system of lower performance at a higher cost.

ADA will allow companies without digital hardware expertise to perform similar feats but with digital amplification and at lower costs. Sony experimented with digital input audiophile speaker systems back in 1998, as did Dunlavy Audio at the 2000 Consumer Electronics Show. Dunlavy showed a modified version of their SC-IVa with S/PDIF digital inputs, digital crossovers, and a Spectron 600 Watt PWM amplifier for every driver.

There are many advantages in designing a multi-amplified system with active crossovers, some of which are listed here. There are extra perks to be gained from implementing some or all of an active system in the digital domain.

Digital amps are smaller, provide more power, produce less heat, and at a lower cost than their analog cousins. There's an inefficient driver you really like the sound of? Go ahead and use it. Want to biamplify or triamplify? Do it for the cost of a single analog amp.

Broader transducer choices for designers. DSPs can provide transparent EQ and crossover flexibility. Know of a driver with great time domain performance, but it's not completely flat? Flatten its frequency response with the DSP. Doing the same complicated EQ in the analog domain can be tricky.

expensive, and degrade sound quality. If ADA becomes pervasive, we may even see new drivers that tradeoff frequency response flatness for low non-linear distortion.

Crossovers impossible for analog designs are possible with digital crossovers. You need 4th order crossover slopes, but like the linear phase properties of 1st order designs? With digital FIR filters you can have both.

More decor friendly packaging could boost sales. ADA solutions could be designed with less boxes and cabling since there are fewer components. Speaker enclosures can be made more acceptable to consumers. Dedicated high power amplifiers can reduce bass cabinet size, and DSP delayed signals can align drivers' output without unusual baffle designs. Wireless networking such as IEEE-1394 could even remove the need for cables from the audio system to speakers with integral amplifiers.

With crossovers determined by coefficients in the DSP code, designers can test many more crossover shapes much faster than before. It's quicker to change coefficients than solder up a new board. Designers could A/B test crossover curves at the press of a button.

See Meridian's site for additional ideas on digital integration.

4. Upgradeable & Customizable speakers.

This could actually create a new trend in the industry. Currently designers spend (we hope) a lot of time measuring and listening to the crossovers before going into production. How many times have we seen a manufacturer release a Mk II, or a factory upgrade to change crossovers in production systems?

With DSP based crossovers, if a revision is warranted it could be published online and downloaded instantly at no cost to consumer or manufacturer. Perpetual Technologies has already started down this path with downloadable codes for their P-1A speaker correction DSP box. A company could treat the initial release of their speakers as a "beta" release. Hundreds of listeners in the field could then provide their input for the next crossover release.

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AUDIO ECONOMICS 101
THE CHANGING FACE OF HIFI HOME THEATER
DIGITAL WAVE
MOORE'S LAW
ACOUSTICAL BENEFITS OF FRONT PROJECTORS

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