Harmony, Chords and Colour

With pricing ranging from $3,500 to $15,000 for components like its 2-channel power amplifiers, and complete home audio and home theater systems costing well into six figures, dedication to top quality in every detail of its products is key at McIntosh. This includes the units’ appearance. On a power amplifier so painstakingly built for quality and durability that its entire front panel is covered by 1/2"-thick glass, it’s important that the meters, text and logo graphics displayed behind the glass are readable, attractive, and just the right color.
McIntosh has devoted the same attention to detail to the displays on its faceplates, as it does to its renowned audio engineering. In 1960, the company went so far as to commission researchers at the University of Michigan to find out what color of light is most visible to middle-aged males, McIntosh’s core demographic. The answer was blue, so the company began putting blue-tinted faceplates on the large power output meters on its range of power amplifiers. This color became so closely associated with the company’s equipment that it came to be known as ‘McIntosh blue’ and started the trend of consumers associating blue light with high-end gear.

Getting Colour Illumination Right
In addition to providing a high degree of light output, it’s important that the backlighting illuminating McIntosh large meters be perfectly uniform and consistent. "Models are designed to be mixed and matched as the customer desires and uniformity between models is critical," says Jim Krmenec, mechanical engineer at McIntosh. "That is why the front panel 3-dimensional look between models is so similar. And when a mix of different models is stacked, it is necessary that there is an evenness of lighting as well as in appearance."

McIntosh used incandescent lamps to backlight its meters for several years, but was never satisfied with the uniformity or consistency of the blue color. Meter color would vary from model to model, and even from unit to unit within the same model series. Also, the meters would have a blue tint around edges that would become progressively more washed out toward the center. (See Figure 1.)

Also, incandescent lamps require a regulated AC power supply so the lamps don’t dim or flicker during peak power requirement by the amplifiers. "Adding AC regulators increases cost and circuit design complexity," says Krmenec. "And integrating the incandescent lamps into the meters and text on the front panels can be? very labor-intensive."

Figure 2: Lumitex? fibre optic panels provide high-brightness and uniform backlighting.

Resolving the Backlighting Issues
To bring the look of the displays up to its stringent quality standards, McIntosh evaluated several alternative backlighting technologies for use in its meters as well as its front panel logo graphics and assorted informational text.

Electroluminescent (EL) backlighting was quickly dismissed due to the electrical noise it produces. When you crank up a McIntosh power amp, it has to be quiet, with no audible hum or electrical interference. Plus, EL has an inherent degradation in brightness over time, and poses a safety issue due to high voltage on the back side of the front panel.

"We did explore the use of molded light pipes and edge-lit plexiglass products using surface mount or directive LEDs," notes Krmenec. "However, there are high startup and high tooling costs here, and more importantly, there is a high minimum order requirement. At McIntosh, we produce limited quantities of each model yearly, which precludes us from purchasing in high volume quantities."

This led McIntosh to look at fibre optic backlighting, a woven, layered panel technology utilizing an LED light source that offered high brightness, long life, low temperature operation, low power consumption, custom color capability and perfect uniformity of luminance and color across the entire surface of the panel. (See Figure 2.)

The Solution
In August, 2001 McIntosh began working with Lumitex Inc. of Strongsville, OH to develop a fibre-optic panel that would provide the proper color mix and intensity for meter backlighting.

McIntosh and Lumitex worked closely together for nearly a year to develop a fibre optic panel that was just right for McIntosh’s requirements. Lumitex was able to provide the custom color mixing McIntosh needed, blending blues and greens together to get just the right color for McIntosh blue.

The solution was a fibre optic panel with two woven layers, with one blue/green layer coming from the left side of the panel and the other coming from the right, with a Mylar reflector in back. (No diffuser was necessary, since the McIntosh meters have built-in diffusing properties.)

Figure 3: The fibre optic panels can be cut to length and die cut for clearance holes, for backlighting the green logo and text on components, such as the new MX135 A/V control center.

There are two LED light sources on each side of the panel – one blue, one green. The woven technology used to produce the panels allows the fibres to be interwoven and optimized for even color mix from the two different-colored LED light sources. The cross-woven strands of fibre go back and forth across the width of the panel. Half of the cross-woven strands on each of the two panel layers are pulled up, and the other half pulled down, to alternately feed to the blue LED light sources (even strands) and the green LED light sources (odd strands).

"Half of the strands on each layer go to the blue LED light source, the other half to the green," explains Krmenec. "It’s a simple and effective solution that, after three years in use, still makes sense and still works really well. We use a Sencore light meter with a computer-based data reference to ensure perfect color matching, and with the fibre optic backlight that Lumitex developed for us, we can electronically tweak the colors just the way we want them.

"In addition to providing the backlighting technology that was most feasible for us," says Krmenec, "Lumitex offered complete customization capability and a phenomenal 4-6 week turnaround cycle for prototypes to help us get where we wanted to be as quickly as possible."

McIntosh has also adapted Lumitex fibre optic backlighting to illuminate the green logo graphic and assorted text on the front panels of its newer models of power amplifiers and audio/visual control centers. "The versatility of the Lumitex panels for text backlighting allows us to cut them to length and to match the application," explains Krmenec. "They can also be die cut for clearance holes." (See figure 3).

Another advantage of the fibre-optic backlighting panels is they significantly reduce the amount of labor required for front panel assembly of McIntosh’s units. The front panel of a recently released new model can be assembled in half the time of the model it has replaced.

McIntosh is using fibre optic backlighting for the front panels in all of its new models, and plans to implement it in all future product upgrades until it will be employed over its entire product line, with Lumitex as its sole source, the company says.?

"We’ve found fibre optic technology to be the backlighting solution we were looking for," says? Krm
enec.

Walter Schulz? is an applications engineer at Lumitex Inc.