15.2.2019

Keeping Installed Audio Simple

Installed audio systems often contain a large number of loudspeakers, spread over a wide area to create an even distribution of audio inside a building or a hall. Traditionally, the challenge in installed audio has been the long distances that can exist between power amplifiers and loudspeakers, with one power amplifier sometimes feeding several parallel loudspeakers. As a result, one cable arrives at each loudspeaker and the system is therefore easily installed by anyone, without the need for a special licence or certification for high voltage or high power electrical work.

When it comes to building systems, two main choices exist – either we have a low impedance loudspeaker directly connected to a conventional power amplifier, or step-up transformers are injected at the power amplifier output and the loudspeaker input. In the first case, in order to cover longer distances, the resistance in the interconnecting cable is reduced by simply increasing the cable thickness - but thick cables can lead to expensive installations. Therefore, using a step-up transformer initially appears to be a feasible solution. The power going into and leaving a transformer is essentially the same (although there are small losses), so when the transformer increases the voltage in the interconnecting cable, a smaller current is needed to deliver the same power - and when the current level reduces, there will be smaller losses in the interconnecting cable.

Remember, the voltage drop in a cable is related directly to the resistance and the square of the current that must be carried, and having the squaring in this equation makes the use of step-up transformers particularly effective - leading to systems requiring only thin cables, even when large power levels are passed to the loudspeakers. This has made ‘constant-voltage speaker systems’ using typically 70 Volt and 100 Volt audio distribution extremely popular. But transformers bring their own challenges, however, particularly relating to audio quality and bandwidth, and very often the phenomenon of ‘hysteresis’ in iron-core transformers introduces unwanted distortion of the audio signal.

As a result, the installed audio industry has been looking for a solution that can combine the benefits of using step-up transformers without their downsides. After the move to digital audio, it soon became clear that this would also be a solution to deliver audio to installed loudspeakers without any degradation along the way. Digital bits do not require a lot of power and can be delivered over very thin cables. However, such a loudspeaker must be active – it must contain its own power amplifier, and running a power amplifier calls for a power supply. There are some installed audio systems on the market that run a custom-connected multi-core cable to the loudspeaker, containing some conductors for the power and others for the digital audio, but these systems require dedicated hardware, and this tends to limit their flexibility and increase the system cost.

So, what would be the ideal solution for these installed audio problems?

Firstly, we should have a distribution system that does not compromise audio quality, does not limit the audio channel capacity of the system, uses standard hardware and cabling to reduce system cost and increase the efficiency of implementation - and only requires one cable into the loudspeaker.

Modern packetized networks, such as Ethernet, are agnostic about the data they carry. They offer all the benefits detailed above, and today they are ubiquitous and are installed into virtually any new building. IP networks are very happy to carry any format of loudspeaker supervision, monitoring, and management data, and Audio-over-IP has become a standard technology - generally considered to offer the highest audio quality without presenting hard technical limits to the number audio channels such a network can carry. This makes standard Ethernet a great candidate for a next-generation installed audio system.

Since we are aiming for a system that only requires one cable to run into the loudspeaker, this cable must also deliver the power we need within the speaker to generate audio. Ethernet networks do offer such power, and this technology is called Power-over-Ethernet (PoE). As the typical CAT cable used in such networks is thin, the conductor cross section is typically 0.15 sq.mm - and this is the only pathway available for the power to move.

When developing our next generation installed audio system, we started by focusing on this power source, since a speaker needs short but large bursts of power in order to deliver the dynamic acoustic output. However, PoE power is limited but can be continuous, so we developed new technology that enables us to transform this constant power source into the dynamic power needed within the speaker.

Genelec’s new Smart IP audio technology platform offers single cable connectivity into installed audio speakers, fundamentally with the same advantages as traditional constant-voltage speaker systems - but with an important technical twist: pristine audio quality is maintained, with no degradation of the audio signal. Additionally, there is no hard, technical limit to the number of audio channels, and all aspects of speaker performance can be continuously monitored and managed - enabling system supervision with third-party software using an API interface within the speakers themselves.

Genelec is already offering sophisticated and reliable acoustic calibration software for high channel count systems, and this know-how will naturally be applied within Smart IP, supporting the measurement methods relevant to the installed audio industry. This calibration system naturally runs over the standard IP network, and also uses the single CAT cable connected to the speaker.

Genelec Smart IP offers installed audio solutions with single cable connectivity but without compromising the audio quality. In order to create a Smart IP network, all we need are standard PoE+ capable IP switch devices. The speakers connect as standard IP devices, and Genelec System Calibration software can find, assign, acoustically calibrate and align all the speakers on the network in a matter of a few minutes, saving a huge amount of system installation time and increasing the quality of the final result.

Genelec Smart IP closes the historical loop – it maintains the simplicity of building installed audio but opens the window to new, uncompromised quality enabled by smart digital design. And since we do not plan to stop here, please stay tuned for more…

 

Aki Mäkivirta

R&D Director