What It Does

At LDI2005, the judges awarded Strand Lighting the Lighting/Entertainment Product of the Year for its C21 Dimmer Rack. The system allows users to freely mix dimmers of any type — both sine wave and conventional — within a single rack. (A new quad SCR module allows SCR-only systems to achieve a density of 192 dimmers in a single rack.)

“Sine wave dimming is both old and new,” says Peter Rogers, vice president of marketing for Strand. “The original resistance autotransformer dimmers were all sine wave devices because the output was an amplitude-modulated sine wave. What we have done is taken that idea and applied modern technology to create a high-density dimmer rack that allows people to have up to 96 sine wave dimmers in a rack and all of the benefits.”

Rogers explains the benefits of sine wave dimming. “The first benefit is silent lamps. The second benefit is low harmonic content on your mains, which means you don't need to have oversized neutrals or K-rated transformers, both of which add significant costs to an installation. These benefits can be pretty significant, because — particularly in older cities — the ability to get power systems into a theatre that can deal with the high harmonic content is very difficult.”

Another benefit and difference over SCR dimmers is the fact that sine wave dimmers are not load-sensitive. A regular SCR dimmer requires a minimum load to operate. That ranges from 40W to 60W, so that they will dim properly. Below that level, you will get flickering and potential problems. “A sine wave dimmer doesn't really care what load is connected to it,” says Rogers. “It could be a 1mW LED; it could be a low-voltage track light; it could be neon or cold cathode. Basically, you can hang anything off this thing that you can hang off an old-style autotransformer. So you can dim a motor with it, or you can control a fan onstage — just a whole host of things.”

The single biggest demand for these products has come actually from acousticians that are designing concert halls. “The noise floor of a concert hall — as they are designing them — has been falling over the years. It used to be NC20 [Noise Criteria]. Now, they are down around NC15,” says Rogers.

There is still a price premium for sine wave dimmers in comparison to a standard module. “It is coming down, but its probably still 50% versus a high rise-time dimmer,” says Rogers.

How It Came To Be

A truly quiet dimmer has been a goal for many dimmer engineers over the years. Acousticians have been demanding quieter and quieter dimmers for years, and high rise-time dimmers of 800 microseconds were not enough to satisfy their acoustical goals. “It really came to be because people were asking for quiet loads in a wide range of applications, from people doing digital audio recording on a movie soundstage to people designing concert halls,” says Rogers. “In Europe, regulations — particularly over harmonic content — were driving more and more systems, especially the largest ones to go all sine wave — so, regulation in Europe and artistic demands here.” Strand starting designing the sine wave product in 2000.

So why has sine wave dimming taken so long to come along? Like many technologies that the entertainment technology industry now enjoys, the costs were too high. “The IGBT [Insulated Gate Bipolar Transistor] devices weren't available. Until recently, they were so expensive that they weren't viable,” Rogers explains. “You need so many high-power capacity IGBTs in a sine wave dimmer — you use four for each dimmer — that it was just too expensive. The costs have come down; the ability to control them is better; and they are much more resistant to cold-filament shock. We spent a lot of time designing them to be resistant to cold filament shock because that's what blows up IGBTs — to be able to use a bump button to have the lights flash up. In early versions, these power devices would just destroy themselves. There would be a little puff of smoke out of the rack and the lamp would literally not even get to full. Now you can do rock ‘n’ roll.”

One of the key features of the TrueSine dimmer products is the fact that they can be interchanged with regular dimmers. This is huge. “One of the things that really drives customers is the ability to mix and match — that you can unplug a sine wave dimmer and plug in a standard or vice versa. You don't need anything special in the dimmer rack. Television people will say, ‘that scoop is making a whole bunch of noise.’ To be able to put a sine wave in to make it quiet is a huge deal for them. The customers on a budget really like the interchangeability,” Rogers notes. “We see quite a mix of installations. I'd say about half are like the Toronto Opera or Nashville Symphony where the whole hall is quiet, and they want all sine wave dimming. The other applications that we see are mixed systems where things like house lights are sine wave, but they did not want to spend the money on sine wave dimming on stage.”

The first sine wave product that Strand developed was the SLD series with 48 sine wave dimmers in a rack. “That was a good first answer,” says Rogers. “Then, all of the consultants came to us and said, ‘Great, now do it with 96.’ We took the SLD circuit design, repackaged it, and put into the C21 product, and now we have 96 dimmers in the rack.”

What's Next

According to Rogers, Strand will be putting the TrueSine into rolling racks. “The first racks will ship in time for the summer movie production season. Later this year, you will see product in different packaging from us. I think that the next big hit is going to be in the small architectural wall racks, where you currently can't get a sine wave dimmer. There are lots of uses for them. It will not be a plug-in rack,” he says. These racks will have bolted-in modules, similar to the Strand Environ product. Rogers continues, “We are looking to build racks that will be all sine wave or mix-and-match regular and sine wave dimmers in those cabinets as well.”

“The SLD sine wave dimmers have been installed in a number of applications, and the newer C21 versions just starting the installation process. We will obviously service and support the SLD product, but the demand for the C21 has pretty much surpassed the SLD demand. We are just finishing off SLD installations because of the construction cycle.”

When asked if he thinks the regulations in America will push for sine wave dimming, following Europe's lead, Rogers replies, “Ultimately yes. Yes, we will.”

What End-Users Have To Say

Richard Hoyes, an associate with Fisher Dachs Associates, has specified a number of projects with Strand sine wave dimming. Currently, he has three completed projects with the dimmers for house lights that include Fairfield Community Arts Center, Fairfield, OH, with 18 dimmers; Georgetown University with 20 dimmers; and Ellie Caulkins Opera House in Denver with 74 dimmers. Later this year, Hoyes has two projects with the C21 sine wave product scheduled to open, including the Four Season Centre for Performing Arts in Toronto with 1,000 stage and house lighting dimmers; and Schermerhorn Symphony Center, Nashville, TN, with 350 stage and house lighting dimmers.

“We have four facilities up and running. They are working great,” says Hoyes. “We had acousticians involved in two of the projects, and they have nothing but good things to say about the noise level.” On the Fairfield project, sine wave dimmers solved a large problem. “During value engineering, they decided to use a cheaper houselight fixture; they used a PAR56 unit that makes a notoriously loud noise. With the SLD system, we could go in and easily integrate 18 sine wave houselight dimmers in the same rack with the other dimmers. This was a change at the last minute. After switching to the sine wave dimmers, the lamps were dead quiet.”

Many of Hoyes specifications are for mixed sine wave and SCR dimming systems. Hoyes comments, “The ability to combine different types of dimmers into single rack is great.” He does have a full sine wave system about to open in Toronto this year. "The Four Season Centre will be our first project that will be all sine wave. This is primarily an opera house, so silence was the key.”

For additional information, visit www.strandlight.com.