Efficiency of air movement

The technology inside audio amplifiers is moving on apace, with more efficient and more powerful electronics and greater connectivity now key features. However, there are also still important compromises that need making in terms of cost, which make amplifiers for installed use quite different from their better looking, live sound cousins.

”We are now at the cross over point where will be switching from one generation of technology to the next.” Stated QSC Audio’s systems specialist Santiago Alcala at the recent Prolight + Sound show. “In terms of installations, we are now talking about integrating all different technologies from lighting, video and audio into shared networks.”

There are undoubtedly exciting things on the horizon from a number of the major manufacturers, of which QSC is one, but certain things will remain the same in terms of the features required of amplifiers for fixed installation.

Cost is the big one for the main stream integration market. However it’s not just headline purchase price and squeezing out the most margin possible that’s important here, but the total cost of ownership. That translates to two things. Firstly, the reliability of a product. Cheap to buy doesn’t mean cheap to maintain and if you’re having to make regular trips to your amp rack to deal with faulty amplifiers, you’re spending money. The second factor, which is of more relevance to the customer than the installer, is energy efficiency. Installed sound systems are often operated 24/7/365 and that means they use a lot of electricity. Anything that will reduce the bill ought to be attractive to a client.

However these days, being bomb proof and cheap isn’t really enough. Modern networking technologies mean that AV devices can be configured, monitored or controlled remotely using PCs, or controllers and amplifiers are no exception. A whole new generation of amplifiers has therefore sprung up to take advantage of this, with the ever-present RJ-45 type connector on the back, and most of the major amplifier manufacturers have offerings in this space.

Crest Audio’s current generation of installation products is the CKi range, it contains three different models. The S model is the low impedance, 8 Ohm version, there is a V model, which serves the direct 70v market in the US and the X range, which is the 100v transformer equipped model. Crest Audio’s Jochen Frohn, explained some of the features that distinguished these products from touring style amplifiers.

“The main thing is that all of the controls and connections are on the back of the amps, with only indicators on the front to demonstrate fault status or whatever. When you set up the amplifier you are working at the back, setting up the cobranet bundles or whatever, and once you’ve done that then you can control the amplifiers via a PC anyway. Of course with all this extra hardware on the rear, there’s not so much space for cooling outlets, so you tend to find installation amplifiers use front-to-side cooling arrangements. This also has implications for rack design. You need to leave space at the side for the air to circulate.

Camco has two distinct lines in the installation market. The Q-Power series is the company’s workhorse. The class D Q-Power 10 offers everything from 100V to 16 Ohm operation, with 4 output channels and max RMS of 2500W. Q-Power 6 doesn’t deliver 100V but its class H output provides 1400W at max RMS. Additional energy efficiency for these models comes from the thermostatically controlled fans in the cooling setup.

The second range is the Tecton series. This is a range of Class AB and H, 2-channel amplifiers rated down to 2 Ohms and delivering up to 1900W of stereo power in the case of the Tecton 38.4. The Tecton amplifiers can also make use of optional plug-in cards (Extendable User Interface cards) to unlock network features such as Audio networking and remote control. One interesting reliability feature is that the Tecton amp’s electronics are suspended from the to of the case, facing downwards so any dust that would normally accumulate over time simply falls to the bottom, instead of sitting on capacitors or heat sinks and reducing their efficiency.

Maintaining our theme of efficiency we arrive at Martin Audio’s MA and Q Series’ series. The MA12K and 18K models claim to offer almost 95% efficiency. They are based on PWM (Pulse Width Modulation) technology combined with a two-stage switching power supply. The Q series of installation products features the patented Class TD technology, which combines the exceptional efficiency of a Class D amplifier with the high sonic quality associated with Class B designs. The Class TD output sections work in concert with the unique regulated switch-mode power supply to create what the company says is a superior overall power amplifier topology. Sagging or fluctuating mains voltage will not affect the power output delivered to the loudspeakers.

Powersoft’s K-series was designed specifically with a number of power saving features in mind. The core of the product is Powersoft’s regulated switch mode power supply with power factor correction and like Martin Audio the company claims it delivers efficiency of around 95%. The power factor corrector forces the current within the amp to behave coherently and in phase with the mains voltage, maximising the drawn power from the mains supply.

Returning to QSC Audio’s Alcala, the company has two main lines of installation amplifier, the ISA and CX ranges. ISA is the cost effective, contracting solution. It comes in four low impedance versions, and an additional 3 Ti models rated for 25, 70 and 100V applications. A unique feature of the Ti series their ability to drive a mixture of 8 or 4 Ohm outputs and a distributed system on the same channel simultaneously. This allows the contractor to reduce the number of required amplifier channels.

CX is a much more fully featured range of products, using QSCs efficient Powerlight technology and featuring so-called Data Ports, which allow the amps to be linked to a QSControl solution or to signal processing units. For 100V use, an external transformer is available, which converts the CX302 to a 400 Watt per channel isolated output.

There are also several contractor friendly features including 1 dB detented gain controls for easily repeatable settings and a custom security cover for tamper-proof installations. Active inrush limiting eliminates AC inrush current, cutting the need for power sequencers.

Yamaha Commercial Audio offers three different product ranges for the install market, depending on price point and application requirements. “The amplifiers for installed use start at the XP range.” Said Scott Fraser, Installation Manager at Yamaha. “That’s aimed around the area of the QSC CX range.” XP ranges in power from 110W per channel to 700W, all at 8 Ohm, and the 350W XP3500 can also be run for 100V in bridged mode.

“Next up is the PC-1N series, with those we can do networking, remotely controlled volume, triggering based on conditions in the amplifier and so on,” continued Fraser. PC-1N is a five model range offering 1600W per channel at 4 Ohm down to 400W. The middle of the range, PC3310N model can be operated in bridge mode for 100V use, and in this state produces 625W per channel.

One interesting feature of Yamaha’s range is the amplifier. Rather than conforming to the standard AB or D nomenclature the company uses its own EEEngine. The company says: “This is a revolutionary power amplifier driving technology that offers the function of a Class AB amplifier and the efficiency of a Class D amplifier. EEEngine gives you fantastic power, highly efficient driving function, and tremendous energy savings, all without sacrificing the sound quality demanded of a professional power amplifier.” EEEngine also has significantly less heat output than conventional power amplifiers, leading to longer lifetimes for the product.

These non-standard power amplification electronics adopted by the likes of Yamaha, and Martin Audio are certainly going a long way to increasing the headline efficiency of amplifiers. However QSC’s Alcala hinted at much broader changes to the way we consider energy efficiency. “Right now we talk about the efficiency of a particular device,” he said. “But I think moving forward we will need to think about the complete system, and also re-examine how we deal with the electrical energy itself. Amplifiers could well come in different forms to the one we currently recognise – the black box – and I think we will also see changes in the way electrical power is distributed, or even recycled between devices in the audio chain.”

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