A constant companion

100v line audio, otherwise known as constant voltage system, has been a main stay of commercial installed sound systems for a very long time. InAVate takes a look at current developments and the future of the technology as digital solutions loom large.

The origins of constant voltage systems are somewhat shrouded in mystery. This venerable technology has been with us since the beginning of the 20th century as an alternative to low-impedance systems for carrying audio. In the US this constant voltage has been 70V whilst much of the rest of the world now uses 100V.

One version of events is that in the 1940s a TOA engineer by the name of Kiyoshi Morimoto conducted an extensive study of the all the various constant voltage options used and concluded that 100v was the most suited. A strong reason for this was that apart from anything else, it’s much simpler to do calculations around a base of 100, than any other number. Morimoto campaigned for 100v to become the Japanese industrial standard, and Europe then followed suit when TOA opened up for business there.

Whatever the case, the technology has been with us for the better part of 70 years. And, even with the threat of fully digital, IP-based solutions looming on the horizon, there’s no reason to believe that this most faithful of servants to the audio contracting industry doesn’t have at least another decade in it.

One reason for its continued success is that it’s simply very good at what it does – delivering audio signals over long cable runs with reasonable efficiency and low rack space. Another reason is that whilst 100v line audio may be a mature technology it certainly isn’t a stagnant one. With nigh on every commercial speaker and amplifier manufacturer offering products in the 100v field, competition for business from distributors and contractors is high, and competition breeds innovation.

In an effort to stand out from the crowd, manufacturers of commodity products such as ceiling speakers have to develop new strategies. One area of competition is customisation, as Sasha Riedling, marketing manager of IC Audio explained:

“Requests for special products account for perhaps 20-30% of our total output. These usually come from our distributors who say ‘here’s a project we could get involved in but we need xyz features from the product.’ The customisation can range from a very simple thing such as a different coloured finish, to saltwater proof speakers for ships, to non-standard power tappings. It’s an important service we offer to our customers. Everyone has standard ceiling speakers. So normally it’s just a matter of price and how fast you can push your product into the market. But aside from that we don’t have many competitors who can offer the same levels of customisation.”

All of the manufacturers will offer some level of colour customisation, it’s been an important market for some time as architects and interior designers create themed environments to a particular colour scheme. According to Bill Web, technical director of Martin Audio, there’s even a market for “nicotine stained yellow” for public houses. However, this particular niche market is likely to be on the down turn given the trend in Europe for banning smoking in public spaces.

Tannoy, RCF, Community – they’re all at it. Lead times on specials largely depend on quantity, and the level of customisation. A simple RAL colour run of 300 speakers from IC Audio might take five days. 2,000 speakers in an unusual colour and different mounting fittings might take three months.

However sometimes it’s not just a matter of a new coat of paint. Penton have been involved in some more radical specials in the past year. The company’s Peter Aubrey-Wright said: “One thing that has been popular of late appears to be mounting loudspeakers in chill beams (a new cooling solution) in open plan office environments. We’ve done a few jobs recently where we’ve constructed cabinets that will bolt onto these beam sections so that we can then mount our speaker in them later on. Alternatively the whole thing can be pre-assembled and installed in one hit. Lighting and speaker cables are now being run through them as well. It provides a very elegant architectural solution to centralise services.”

At the very top end of the “specials” tree are completely custom products. Sometimes there just isn’t a speaker that will do the job, or there used to be and there isn’t any more – a case that Aubrey-Wright has experienced. “We have been asked to produce a similar product to one that had been discontinued by another manufacturer. We were given an idea of the electro-acoustic performance required and then we made samples followed by a limited run of the product. These kinds of products generally don’t make it into the standard portfolio unless there’s a huge demand. Normally we hold onto the designs for a rainy day when someone asks for something similar.
“I think our ability to produce specials is an important service. Directly they don’t make us a great deal of money but if a consultant or client knows we can, then they are more likely to come to us with other work.”

Customisation can set companies apart, but the ultimate decider will always be the product itself. Manufacturers of both loudspeakers and amplifiers continue to improve the quality of design and components in their products whilst competing on price.

RCF’s Technical Manager, Antonio Ferrari gave an example: “We are always looking to improve even the humble ceiling speaker. For example in our monitor Q series we aimed to produce a speaker with good aesthetics, good design and that was easy to install. A ceiling monitor is normally 4-5kg in weight and therefore requires extra safety cables to hold them up and so forth. However, our model is 2kg so you can install it just like a cheap 6W speaker.”

Easy installation is a significant issue for ceiling speakers as a minute or so saved per speaker in a 500 speaker installation is a lot of time. Another way to reduce cost is to simply reduce the speaker count. Ferrari states that RCF are also working on products with wider coverage and more homogeneous SPLs enabling a reduction in speaker count for a given area. These products will be more expensive per unit, but if a consultant can be persuaded to specify fewer speakers to accommodate their increased power, the savings are there for the customer.

However the loudspeaker is just one half of the 100v equation. At the other end of the line lies the amplifier. Here too technological innovation continues. Rack space is at a premium in any AV system and PA / VA is no exception. Unfortunately the transformer, which forms the heart of a 100V amplifier, is also a large and hot component.

Ian Bridgewater of TOA UK explained how the company were overcoming this particular hurdle: “We’ve just introduced the DA series of transformer-less digital amplifiers. The 1000W version has 4 x 250W amplifiers in a 1u space. That’s up to ¼ of the size you’d expect. The beefier, 2000W version holds 4 x 500W class D amplifiers in only 2u. If you reproduce that space saving in a big system you are drastically cutting down rack space.”

So why isn’t everyone doing this? Neil Jarvis XXX XXX from Baldwin Boxall explains: “Whilst you can save a lot of heat and space by removing the transformer from the amplifier one thing it does give is electrical isolation. If you take the transformer out there’s the potential for very high current draws, which could be potentially very dangerous. You need some form of current limiting device in the amplifier.”

However a circuit breaker or other device then leaves open the possibility that the amplifier would cease operating due to a current surge - not ideal for a life safety system.

Energy efficiency is also a key point for amplifier manufacturers. Michael Roffler Technical Director of G+M Elektroniks explained: “The power consumption of the amp is critical because everything has to have a battery backup. If you are using a type A or B amplifier eating a lot of power, your UPS life is much shorter - no good for an emergency system.”

G+M Elektroniks specialise exclusively in 100V products for voice alarm and emergency systems. Their latest amplifier operates at an efficiency of 92% at full load. It’s based on a class T amplifier, and compares to around 80-85% for the class D amplifiers used by the majority of the market.

So, 100V equipment continues to get more efficient and more cost effective. With the continuing developments in 100V amplifier and speaker technology, the quality of the audio reproduced is also on the up, when compared with low-impedance systems. IC Audio’s Riedling elaborated: “When comparing low-impedance and 100v products you have to split 100v up into two groups. For full range speakers I would say that there is still no comparison. However, the 2-way products are really fine music products and the gap is now very small. The trend here is definitely towards higher sound quality. We have customers asking for quality sound in bards and restaurants and they still want to use 100V.”

However whilst products are improving the unit price is not coming down massively. This comes back to our old friend the transformer. In both amplifier and loudspeaker the transformer makes up the majority of the cost. Ever increasing industrial output from China is putting an exponential strain on the world’s copper supplies, the material from which transformer coils are made, driving up prices. In the end this is what may spell doom for analogue 100V line audio.

Already available in the market are products using digital amplifiers, which can be mounted directly onto a loudspeaker and are no larger than a cigarette packet. Clearly the concept of an active loudspeaker is not new, but it is when we’re talking about an 8W, ceiling speaker. At present these products are expensive, and not widely accepted by the life safety and voice alarm fraternity. However all the major loudspeaker manufacturers are either producing product, or in research and at the rate that electronics depreciate in price there will come a point where the cost of these products is down to a level where the advantages of digital systems are overwhelming.

Estimates vary as to when that point will come. But a time scale of 3-5 years seems popular for when we’ll start to see digital systems in reasonable use. However that won’t be the end of 100V. There will still be many applications where it’s the best solution for some years to come. Many observers also suggest that we’ll see hybrid solutions of 100V and digital technology. Almost all agree that whilst digital is coming, 100V will be with us for at least another ten years, probably more.

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